Schedule January 2007
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Wed Jan 03 - general, Thu Jan 04 - Tape Team, Wed Jan 10 - general, Thu Jan 11 - Tape Team, Sat Jan 13 - 2nd Sat., Wed Jan 17 - general, Thu Jan 18 - Tape Team, A Proposed Demo, Sat Jan 20 - Ron & Bob, Wed Jan 24 - general, Thu Jan 25 - Tape Team, Sat Jan 27 - 4th Sat. Wed Jan 31 - general,
Wed Jan 03 - general,
- Present were: Allen Palmer, Bill Flora, Glenn Lea, Robert Garner
- In the morning, Bill Flora ran the 1402 Card Reader Ripple Test again with no failures.
- (The Group Mark test deck causes occasional errors. A card of all group marks causes a mis-read. )
- Allen Palmer ("Mr. Neat") has installed a pegboard for hanging his tools.
- (Now it will be easier the "borrow" from Allen than Ron Williams :-))
- Message from Robert Garner January 03, 2007 3:32 PM
Woz (w/ John [Toole]) did stop by for about half an hour!
He totally enjoyed the system, asked lots of questions, and had many interesting observations.
When I discussed future 1401 system programming classes and demos, he remarked that
- "the working 1401 will be the best part of the Museum"!
He thought the 1401 classes should begin with transistors, SMS cards and on up!
(image sent Jan 24th)
Bill and Glenn were getting card reader check errors again (while trying to get something to demo for Woz.)
Perhaps because we had the system off for several hours (putting 1402 skins back on) and it hadn't warmed up?
I asked Bill to give Ron a call tonight on 1402 status.
Also, Allen noted that the TAU causes the 729 to stretch tapes (again).
p.s. We need Ron's "power's of 2" print program next to the 1401 so we can toggle it in on short notice.
Thu Jan 04 - Tape Team from Bob FeretichTAU Debug Status - (Ron W. & I)
The "tape stretching" that was reported yesterday was not a problem for us. We "loaded" tape about a dozen times today. The tape was smoothly drawn into the columns every time except once. That time the supply column stuttered once then loaded.
We observed that the TAU's skew and error indicators were stuck on. This was a new problem that cropped up sometime in the last three weeks. We traced the problem to two bad cards (a 3-input NOR on one card and a 2-input NOR on the other). These two NOR gates are cross wired to form a set-reset latch. The outputs of each of these gates were stuck minus (-5.8 volts). Either of these gates having its output stuck minus would cause the observed failure. It is curious that both of these cards (card bags labeled 02b3c15 & 02b3f15) failed within three weeks of each other. Coincidence???
During the last work session I fixed a card punch error in the Move Tape (5040) diagnostic, but was unable to verify the fix. Today, we loaded and verified this fix.
We set the sense switches to continuously repeat the Move Tape diagnostic and ran it for nearly the entire length of a tape. (about 10,000 fifteen-character records) For this diag, a record is written, the tape is backspaced, the record is read and compared, and then the sequence is repeated with a different record.
Results of the long diagnostic run:
- Sixteen error clusters occurred. Each cluster consisted of three to eight consecutive failing records.
- Bad spots on tape caused some of these error clusters. (Fewer errors occurred as we moved deeper into the tape.)
- Eight of the clusters showed a write/read data compare failures on the first record of the cluster. No other data compare failures occurred. Other errors were parity or skew errors.
- On most data compare errors, a single bit was picked or dropped. Picking the A-bit was most common, but sometimes the A-bit was dropped. Sometimes the entire record was trashed.
- Scoping the OR of the received clipped data bits shows that all bits of a character arrive within a 2.5 microsecond window. We were running at 556 cpi density (about a 22 microsecond character frame). I don't know if this is within specifications, but at least one skew error was reported.
- Frequent CPU A-Reg errors occurred. (TAU read data is delivered to the A-Reg.) The error indicator glowed dimly during the entire run. These errors were not being reported in the TAU error indicators nor printer report.
- Printing an error report line often turned on the "Printer Check".
- The diagnostic finally crashed when the 1401 CPU branched into the print buffer (201- 332) and loaded a Group Mark as an opcode. The error report showed that a longer than 15-character record was read just before the crash. Data read from the tape is transferred directly into the print buffer. The program starts at about address 400. It is possible that the erroneously large incoming record trashed the beginning of the program, but a Group Mark with a Word Mark should have protected the program.
We disparately need spare TAU SMS cards. There were no TAU cards in the Repaired Cards box. Only two TAU cards were in the BAD Cards box. I found a batch of bagged bad TAU cards in the rolling shelf unit. It looks like they were removed from the Bad Cards box so that they would get higher repair priority, but put aside and forgotten. I placed them back into the Bad Cards box (they are all labeled TAU). We would appreciate getting these cards repaired ASAP.
Wed Jan 10 - general
- Present were Ron Williams, Bob Erickson, Ed Thelen, Frank King, Chuck Kantmann, Bill Flora, Allen Palmer, Robert Garner.
We came in and were shocked to find Allen's neat corner even neater. This is not fair!! I mean like humiliating.
- Allen and Ed finished connecting power supply wiring on the second 729 Mod V tape drive (Allen Plamer on the floor with screw driver, Ed Thelen in comfy chair reading disconnect log entries - this is the best way to do it - according to Ed.)
After that power supply was connected, Allen got Frank King and Bill Flora to help lift another power supply into another 729 tape drive. Ron Williams stood by with 2x4s, ready to play Archimedes. Sounds simple and quick for folks used to 8 pound PC power supplies - BUT we are dealing with ?250? heavy honkers (I'm bringing a bathroom scale Saturday to weigh one) that are big and clumsy. Get a finger under that turkey and the memory will last as long as you do!! Not quite as awkward as an auto engine.
Allen and I spent a long time trying to get that power supply secured (bolted down). The power supply has a flange under a 6 inch shelf about 1.25 inches high. This flange has two slots held down by four little bolts. Trying to manipulate those two little bolts that can only be held with the sides of two fingers is difficult - well #$%^&* - I guess that is what surgons learn and practice. Then you try to torque 'em a little. :-((
- OK - Allen wound up doing it. :-((
- The 1402 had been getting error checks last session after Bill had remounted its covers, just, of course, before Steve Wozniak arrived! Ron Williams and Bill Flora considered actions: After examining card-to-printer results, they zeroed in on the problem and pushed in a loose control-wire pin in the reader unit. The wire is very taught and installing the cover bumped it loose. Bill remarked the wire should be lengthened.
- A card of all group marks causes a mis-read. The -21 volt power supply in the 1402 reader drives current through the read brushes and through magnetic core memory during a card read cycle. We have discussed measuring currents in memory (voltage across limiting resistors in series with wires through cores).
- Frank King talked with others about changing the 083 sorter from 50 Hz to 60 Hz. This involves "re-tuning" the feroresonant regulator (we have no experience - but some of us would like some), and changing the drive pulleys due to the higher speed of the motors. The sorter was left plugged into the utility outlet of the 1402 reader/punch.
- Robert Garner went upstairs to present to the administration Bob Erickson's request to restore a newly arrived IBM 513 duplicating/summary card punch, currently with a newly arrived IBM 403 accounting machine. About 2:30 Kirsten Tashev arrived at the 1401 area and went with Bob Erickson into Invisible Storage to view the newly arrived IBM 513 and discuss why restoration for usage by the 1401 team would be a good idea. (Bob watched for this old stuff like a hawk!!) Bob found that the 513 is crankable but rather stiff - maybe 40 years of drying/oxidizing oils and greases are responsible. We were later joined by Al Kossow.
Bob's Rational for restoring a reproducing card punch
- (A reproducing card punch can take one deck of cards, and duplicate it by punching appropriate holes in another blank card deck.) (This is especially important in "object" decks that are run frequently - like every day.)
- As decks of cards are read through any card reader, even the 1402 card reader, wear occurs and eventually the deck becomes marginally readable and should be reproduced. Kirsten asked why the 1401 reader/punch (the 1402) could not be used to do this necessary reproduction? Bob answered that the 1402 punch is not as robust as the punch unit in a reproducing punch.
- A likeness of an old fashioned "Tab Room" would be incomplete with out a reproducing punch.
- Robert Garner wants me to get the simulator demo program punched via ?CardAMation? and available for demo. I mentioned that the card reading was faked, as the simulator in ROPE does not currently support card input. (Ron Mak proposes a work-around.) Robert suggests that Ron Williams visually check the card reading code, assemble it in ROPE, give the results to Bob Feretich for conversion to whatever, then to CardAMation, and hand fix anything necessary. Will try soon.
Status of machine when we left - Card Reader pretty good, might have to read a program deck twice, Processor seemed to work, Printer - powers of 2 and printer art printed just fine. (People seem to forget that we can order and get delivery of folded tracker printer paper suitable for the 1403 from Office Depot :-))
- A study of the IBM 513 Summary (and Reproducing) Punch, newly arrived in invisible storage
513 Name Plate
513 Front View
-w Patch Panel
513 Back Gearing
513 Motor Generator
- A study of the IBM 403 Accounting Machine, newly arrived in invisible storage
403 Printer Tractor
-w Patch Panel
403 Card Reader
403 Right Side View
Thu Jan 11 - Tape TeamTAU Debug Status 1/11/07 - (Ron W. & me)
We started out a few steps back again today. Characters that we read were received with their 8-bits set to zero. The failure was consistent so it was not too difficult to troubleshoot. We isolated the problem to a jumper wire on the back of the 729's read amplifier gate. The pin socket that was crimped onto the wire was failing. Wiggling the wire at the socket made and broke the connection. There was even a state that passed an attenuated signal. This may have been responsible for some of the intermittent errors that we saw in previous weeks.
We then ran the Move Tape diagnostic (5040) for a good portion of the tape without error. Previously this diagnostic seemed to cause a large number of 1401 A-Reg parity errors. None of these errors occurred during this run.
We ran the Card-to-Tape (5000). Eight to sixteen errors were reported each time we ran the test. The most common error seemed to be TAU compare errors with the TAU's A-Reg set to 0000001 and its B-Reg set to 0000000. Neither of these characters are legal, so we think that the TAU is sampling data when it not supposed to. These errors occur on the read back part of Write instructions. The error is probably occurring in the read back timing. The primary difference between this test and Move Tape is that the tape operations in Move Tape occur more quickly so the tape flows smoothly. Card-to-Tape incurs a card read delay between each record, causing the tape prolays to chatter. We checked the Write Delay and the Write Disconnect Delay. They look ok. The root cause is still TBD.
Other strange things we observed:
- We were running Card-to-Tape with the read back sense switch (G) on. After several minutes of running, the 1401 jumped to execute a Group-Mark with Word-Mark instruction in the print buffer. We verified that the begining of the diagnostic was not corrupted. We also saw this happen once last week with the Move Tape diagnostic.
- Twice today the 729 lost Ready status for no apparent reason.
- We ran the tape off the end of the reel. It took a lot of messing with the 729 to reset it after that. (Including a few power off/on cycles.) I am not sure what we did to reset the drive. I have also seen this happen several weeks ago.
- On occasion, the 729 refused to Unload tape. I think this a problem with the mercury switch on the back of the take-up shaft. I adjusted it so that the contacts were horizontal and the problem went away. Might be a fix or a coincidence. We need to wrap the switch's bulb in something tacky so it neither slides nor rotates in its clip.
- We accidentally executed a Rewind operation using the address of the 1402 Card Reader. Several cards got mangled as they were sucked up from the output hopper.
Sat Jan 13 - 2nd Sat
- Present were: Ron Williams, Bob Erickson, Tim Coslet, Ed Thelen, Grant Saviers, Jeff Stutzman and Ron Crane.
- As promised, we weighed a 729 tape drive power supply - with a bathroom scale. It weighs 140 pounds. Well, OK, that is about 2.3 60 pound bags of cement - and just about as easy to handle.
- About one hour after starting the 1401, it began misbehaving :-(( - classic temperature sensitivity. Ron Williams finally traced it down to one transistor in the Overlap system affecting the Storage Address Register (STAR). Chill the transistor and the machine works, heat the transistor and the machine fails. The transistor leaked too much as the temperature rose :-((
The red line in the right hand screen shot is where the base line should be. The leaking transistor floated the base line (a 'false' value) up (into the 'true' range) confusing the machine.
Tim Coslet expressed frustration trying to test the double sized SMS cards with out a test fixture to aid making power and signal connections. After some discussion, Grant Saviers will make a double wide test fixture somewhat similar to the single size SMS test fixture made by Ron Williams (with lead in the base to increase stability ;-)) Grant plans to use two SMS sockets rather than the green S-100 BUS socket shown.
This is an overview of the south west corner of the 1401 room - with some serious folks. Tim Coslet (left) and Ron Crane are fixing sick SMS cards.
Bob Erickson and Jeff Stutzman worked on the plastic shield for demonstrating the 077 collator. Jeff came up with the ideas of:
- - use chrome edges to hide the glued corners
- - use thin lamps under the chrome edges to light the machine
And no, the 077 was not modified to install the plastic. The brackets are part of the machine to secure the normal metal "skins". Some extenders were crafted to better place the plastic.
Wed Jan 17 - general
- Present were Ron Williams, Bob Erickson, Frank King, Glen Lea, Chuck Kantmann, Bill Flora, Robert Garner, Ed Thelen.
- Grant Saviers brought in a "1401 SMS Test Fixture" which we had requested just last week. Talk about prompt design, fabrication and delivery!!
Grant also brought in a Tektronix TDS 220 two channel sampling scope - purchased via e-bay!!. Something about 100 megahertz capability, which should work well on our 87 kilohertz machine - talk about 10,000-1 oversampling ;-)) The machine is not a "scope" - in that there is no long CRT - it is very light and very handy :-))
Bob Erickson and friends finished up enclosing the moving parts of the 077 collator in sheet plastic. And moved it to a prominent place at the entrance of the 1401 room. Really Great historical sequence :-))
- Ron Williams found a card in the 1401 that was occasionally causing the 1402 Card Punch to punch in wrong rows (like row 13 ;-))
- The above is the good news. Most of the others left to miss the commute traffic, but Ron Williams, Bob Erickson and Ed Thelen stayed on to struggle with the flaky 1402 card reader. The 1402 card reader and/or electronics is just not reliable. Frequently rather small test decks (to test other functions) do not get read correctly and must be re-read to get the test to run. (1401 "object" deck do not have sum checks, but depend upon a reliable card reader and the read check system.)
There was a hypothesis that sagging 21 volt power supply might be causing the Group Mark sensitivity. A group mark in a punched card has two successive holes, (eight and seven) and one other hole. Cards with mostly group marks seem[ed] to get misread more than other cards. (A card of all slashes also has successive rows punched out (zero and one)).
Ron Williams points out that testing with group marks has the advantage that the group mark is non-printing, and that most mis-reads of a group mark character (in the sense of missing a punch) yields a printable character, except of course missing all three punches which will also print as a blank. (Much easier to visually check and analyze.)
So we read and printed a deck of cards with all group marks - and watched the output of the 21 volt power supply.
Characteristics of the errors as printed on the printer (about 100 lines/test)
- The scope, set on DC, 5 volts/cm yielded no apparent sag or other interesting news.
- The scope, set on AC, 0.1 volts/cm yielded some 0.03 volt spikes, but that did not seem consistant with reading blank cards vs group mark cards.
- Placing a additional 0.8 amp steady load across the power supply caused a 0.8 volt DC sag, but no apparent change in the read error rate.
- It was also noted that voltage sag was not the likely problem as the row 8 seemed as likely misread as row seven - or even row 12 of the group mark character.
- (There seemed bursts of high frequency noise that we could not sync on - maybe artifacts from building electrical noise???)
Print outs of the Group Mark Tests
- Errors were not "random" or "Gaussian".
- About 6 lines per 100 had errors (one or more printed characters)
- If a line had an error, there was a 50 % chance of having more than one
- One or two lines per 100 had 10 or more errors
- There was a noticeably higher density of errors on the right hand side of the page
Executive Summary So I (and Ron Williams and Bob Erickson) decided that the 21 volt power supply was not likely the culprit in the bad read error rate.
So - now what???
Bob Erickson carefully examined the test deck for hole alignment. It was not particularly good, not bad.
- Bob suggested we flip the deck side for side (the 80 column is now the 1 column) and most the errors now appeared on the left side of the print out. - Previously most of the errors had appeared on the right hand side of the print out.
Bob Erickson tried an old CE trick of looking for where the brushes were contacting the card, relative to the holes. He took some grease and smeared it lightly over a row of holes, and read the card. The brushes dragged some of the grease further down the card, making the brush traces visible.
- Bob thinks the read brushes are slightly mis-registered relative to a properly punched card. The amount of mis-alignment should not be causing our torment.
- Ron Williams and Bob Erickson are planning to come in this coming Saturday. - More card reader??
Thu Jan 18 - Tape TeamTAU Debug Status - 1/18/07
The new sampling scope that Grant brought in works great. It was essential for troubleshooting the intermittent bug described below.
The WriteTapeMark (WTM) instruction was not working. When executed the CPU hung waiting for the TAU to complete the instruction. I replaced a card in the WTM logic to fix the problem.
I erased the entire tape, then executed a read record operation from the TAU control panel. One of the manuals recommended this technique to troubleshoot intermittent errors. A specific error occurred frequently. The error indicators were: Error - on
A Reg VRC error - on
R/W Reg VRC error - on
A Reg = 0000000
B Reg = 0000000
R/W Reg = 0010000
The A, B, and R/W registers are reset to zeros at the beginning of a character time and bits are set to one based upon the character received on the Tape Channel Read Bus. This is interesting because data from the 729 passes through the A-Reg or B-Reg to get to the R/W-Reg. I set the scope up to trigger on activation of the Error latch and started looking for the cause of its activation. I found a 1 microsecond glitch that occurred 85 microseconds before the Error latch activated. The glitch originated in the 729 and was passed through the A-Reg, but was too narrow to trigger the A-Reg latch. Either the R/W-Reg latch was faster or the logic along the path stretched it slightly.
The glitch's root cause was noise in the 729's read pre-amp. The gain on all the read pre-amps were set much too high. Instead of 8Vp-p, the signals (measured at the 1401 to 729 interface) were 12 to 14Vp-p.
We previously set these levels to 8Vp-p, but I think that we made substantial 729 power supply adjustments after that. The adjustments must have seriously impacted the levels of these signals. I remember during our first the pre-amp level adjustment, the adjustment pots were set at their upper limits to obtain the 8Vp-p level. Now the pots are set much closer to center.
After these level adjustments, the above error still occurred, but much less frequently.
I then ran the tape diagnostic battery as a batch. Move Tape, Load Tape, and Tape VRC diagnostics ran without error. The Backspace/Skip diagnostic was last in the batch and the card reader started mis-behaving. After several read attempts I got this diagnostic loaded, but multiple errors were reported. I am not sure that the diagnostic program loaded correctly.
I did not try to run the Card to Tape diagnostic today.
A Proposed DemoThe following is a Demo of a proposed demo of the 1401 system - a) Guests enter the 1401 area and are introduced to the 1401 and card processing in general b) Guests are invited to key punch their name(s) onto an IBM card starting at column 1 c) The guest's name card is inserted into the demo deck, which has already been set up with a date card - There is one card run per guest card, - The first name in the guest card (say "Steve") is printed in double sized BIG characters - The second name (say Wozniak) is printed further down the page in double sized BIG characters - A fixed greeting is printed in single sized BIG characters - The date card is printed in single sized BIG characters - The rest of the deck (pairs of 65 column data cards) are printed in normal print 130 characters wide. This text is by Robert Garner, introducing the 1401 d) Each guest gets to keep the IBM card the guest punched, and the printout :-))The following in an example
SSSSSSSS TTTTTTTTTT EEEEEEEEEE VV VV EEEEEEEEEE SSSSSSSS TTTTTTTTTT EEEEEEEEEE VV VV EEEEEEEEEE SS TT EE VV VV EE SS TT EE VV VV EE SS TT EE VV VV EE SS TT EE VV VV EE SSSSSS TT EEEEEEEE VV VV EEEEEEEE SSSSSS TT EEEEEEEE VV VV EEEEEEEE SS TT EE VV VV EE SS TT EE VV VV EE SS TT EE VV VV EE SS TT EE VV VV EE SSSSSSSS TT EEEEEEEEEE VV EEEEEEEEEE SSSSSSSS TT EEEEEEEEEE VV EEEEEEEEEE WW WW OOOOOO ZZZZZZZZZZ NN NN IIIIII AAAAAA KK KK WW WW OOOOOO ZZZZZZZZZZ NN NN IIIIII AAAAAA KK KK WW WW OO OO ZZ NN NN II AA AA KK KK WW WW OO OO ZZ NN NN II AA AA KK KK WW WW OO OO ZZ NNNN NN II AA AA KK KKKK WW WW OO OO ZZ NNNN NN II AA AA KK KKKK WW WW WW OO OO ZZ NN NN NN II AA AA KKKK WW WW WW OO OO ZZ NN NN NN II AA AA KKKK WW WW WW OO OO ZZ NN NNNN II AAAAAAAAAA KK KKKK WW WW WW OO OO ZZ NN NNNN II AAAAAAAAAA KK KKKK WW WW WW OO OO ZZ NN NN II AA AA KK KK WW WW WW OO OO ZZ NN NN II AA AA KK KK WW WW OOOOOO ZZZZZZZZZZ NN NN IIIIII AA AA KK KK WW WW OOOOOO ZZZZZZZZZZ NN NN IIIIII AA AA KK KK V V III SSSS III TTTTT EEEEE DD TTTTT H H EEEEE CCC OOO M M PPPP U U TTTTT EEEEE RRRR V V I S I T E D D T H H E C C O O MM MM P P U U T E R R V V I S I T E D D T H H E C O O M M M P P U U T E R R V V I SSS I T EEEE D D T HHHHH EEEE C O O M M M PPPP U U T EEEE RRRR V V I S I T E D D T H H E C O O M M P U U T E R R V V I S I T E D D T H H E C C O O M M P U U T E R R V III SSSS III T EEEEE DD T H H EEEEE CCC OOO M M P UUU T EEEEE R R H H III SSSS TTTTT OOO RRRR Y Y M M U U SSSS EEEEE U U M M H H I S T O O R R Y Y MM MM U U S E U U MM MM H H I S T O O R R Y Y M M M U U S E U U M M M HHHHH I SSS T O O RRRR Y Y M M M U U SSS EEEE U U M M M H H I S T O O R R Y M M U U S E U U M M H H I S T O O R R Y M M U U S E U U M M H H III SSSS T OOO R R Y M M UUU SSSS EEEEE UUU M M JJJ AAA N N U U AAA RRRR Y Y 33333 222 000 000 77777 J A A N N U U A A R R Y Y 3 2 2 0 0 0 0 7 J A A NN N U U A A R R Y Y 3 2 0 00 0 00 7 J A A N N N U U A A RRRR Y Y 3 2 0 0 0 0 0 0 7 J AAAAA N NN U U AAAAA R R Y 3 ,, 22 00 0 00 0 7 J J A A N N U U A A R R Y 3 , 2 0 0 0 0 7 JJ A A N N UUU A A R R Y 333 , 22222 000 000 7 TEXT BY ROBERT GARNER IBM 1401 THE IBM 1401 "DATA PROCESSING SYSTEM", INTRODUCED IN OCTOBER 1959, WAS THE "MODEL-T FORD OF THE COMPUTER INDUSTRY" AND "ONE OF THE MOST IMPORTANT AND SUCCESSFUL PRODUCTS IBM HAD EVER ANNOUNCED." ABOUT 15,000 1401-FAMILY COMPUTERS WERE MANUFACTURED AND DELIVERED WORLDWIDE IN THE 1960'S, FAR EXCEEDING INITIAL EXPECTATIONS. BY MARCH 1961, AFTER ONLY A SINGLE YEAR OF FULL PRODUCTION, 2,000 MACHINES HAD ALREADY BEEN DELIVERED TO CUSTOMERS. BY THE VERY NEXT YEAR, 1962, INCOME FROM THE IBM 1401 SURPASSED OLDER CARD-PUNCH/UNIT-RECORD ACCOUNTING MACHINES FOR THE FIRST TIME. BY 1964, 40% OF ALL EXISTENT COMPUTERS WERE 1BM 1401-FAMILY MACHINES. ITS FOLLOW-ON FAMILY COMPATABLE MACHINES, 1410, 1440 AND 1460, WERE SOLD UNTIL 1970. THE 1400 FAMILY WAS SO SUCCESSFUL THAT IT LED TO THE INDUSTRY'S FIRST PROGRAM-COMPATIBLE COMPUTER CLONE, THE HONEYWELL H-200, OR "LIBERATOR." A RUMORED 1480 WAS DISCONTINUED IN FAVOR OF THE 360/25. THE GOAL OF THE 1401 DESIGN WAS TO OFFER A FLEXIBLE BUSINESS COMPUTER OF AT LEAST THREE TIMES THE SPEED AND AT LOWER COST THAN THE UBIQUITOUS, CARD/UNIT-RECORD, COLLATE/MERGE/PRINT, PLUG-BOARD-BASED ACCOUNTING MACHINES OF THE 1950'S (SUCH AS THE IBM 407 AND 604). ALTHOUGH OFFERING A GENERAL-PURPOSE COMPUTER WITH PROGRAMMABLE MAGNETIC-CORE MEMORY WAS A COST RISK, BY CLEVER ARCHITECTURE DESIGN AND USE OF MODERATE-SPEED, ECONOMIC TRANSISTOR CIRCUITS, THE GOAL WAS ACHIEVED. BY FIRST READING CARD/UNIT-RECORD INFORMATION INTO THE MAIN MEMORY OF THE 1401 BEFORE MANIPULATING IT, COLLATE/MERGE/PRINT OPERATIONS WERE MUCH FASTER THAN ON THE OLD CARD MACHINES. AND THE DATA COULD BE QUICKLY ACCESSED TO/FROM MAGNETIC TAPE FOR STORAGE - MUCH FANTER THAN HANDLING DECKS OF CARDS (WHICH ALSO WORE OUT AND HAD TO BE REJUVENATED VIA DUPLICATION). THE 1401 ARCHITECTURE WAS DESIGNED FOR EFFICIENTLY HANDLING BUSINESS DATA-PROCESSING APPLICATIONS. ITS CENTRAL PROCESSING UNIT (CPU) CAN EFFICIENTLY MANIPULATE VARIABLE-LENGTH CHARACTER STRINGS AND PERFORM VARIABLE-LENGTH DECIMAL ARITHMETIC (UNLIKE TODAY'S FIXED-WIDTH BINARY ARITHMETIC). FOR INSTANCE, THE CPU CAN OPERATE ON TWO NUMBERS WHERE EACH IS OF AN ARBITRARY LENGTH OR NUMBER OF CHARACTERS. A 1401 CHARACTER IS ENCODED IN 6 BITS, AN END-OF-WORD "WORD MAKE" FLAG BIT, AND A PARITY CHECK BIT. NOTE THAT EVEN THOUGH A CHARACTER WAS 8 BITS WIDE, THE TERM "BYTE" HAD NOT BEEN INVENTED YET. 1401 SYSTEMS COULD BE CONFIGURED WITH 1,400 TO 16,000 CHARACTERS OF MAGNETIC CORE MEMORY (4,000 MIN TYPICAL). MEMORY IS ADDRESSED VIA DECIMAL CHARACTER STRINGS, NOT BINARY DIGITS AS IN NEARLY ALL CONTEMPORARY COMPUTERS. MAGNETIC CORES RETAIN EITHER A "1" OF "0" DEPENDING ON THE CLOCKWISE OR COUNTERCLOCKWISE DIRECTION OF THE STORED MAGNETIC FIELD. AN EXALTED FEATURE OF THE 1401 WAS ITS RELIABLE AND ROBUST INPUT/OUTPUT PERIPHERALS - A LONG IBM TRADITION INCLUDING AN 800-CARD PER MINUTE CARD READER, A 250-CARD-PER-MINUTE CARD PUNCH, A 600-LINE-PER-MINUTE LINE "CHAIN" PRINTER, UP TO SIX REEL-TO-REEL TAPE DRIVES, AND A 20-MILLION-CHARACTER MAGNETIC DISK STORAGE UNIT. THE SYSTEM AND PERIPHERALS CONTAINED CONSIDERABLE ERROR CHECKING LOGIC. THE 1401 MAY HAVE BEEN EQUIBALENT TO THE MODEL-T IN POPULARITY FOR IBM, BUT WAS FAR MORE COMPLICATED TO MANUFACTURE. WHEREAS THE MODEL-T HAS ABOUT XX COMPONENTS, A LARGE 1401 SYSTEM COMPRISES ABOUT 20,000 MECHANICAL PARTS AND ABOUT 50,000 ELECTRICAL COMPONENTS (10,000 TRANSISTORS AND 14,000 DIODES ON 3,000 CARDS). A TYPICAL, 4K-CHARACTER 1401 SYSTEM RENTED FOR ABOUT $7,000 PER MONTH IN THE 1960'S, EQUIVALENT TO $42,000 PER MONTH IN TODAY'S DOLLARS (6X DUE TO INFLATION). THIS RENTAL FEE INCLUDED MAINTENANCE SERVICE AND OPTIONS FEATURES. A TYPICAL 1401 SYSTEM WOULD HAVE COST ABOUT $370,000 IF PURCHASED OUTRIGHT IN 1961 OR $2,240,000 IN TODAY'S DOLLARS. MOST SYSTEMS WERE RENTED, A "CASH COW" FOR IBM. MAIN MEMORY ITSELF WAS VERY EXPENSIVE IN THE 1960'S: ONE 8-BIT CHARACTER OF 1400 CORE MEMORY IN THE 1960'S COST ABOUT FIVE DOLLARS (OR $30 TODAY). THIS IS 300 MILLION TIMES MORE EXPENSIVE THAT TODAY'S COST OF MEMORY (ABOUT 0.1 MICRO-DOLLARS PER BYTE).
The card deck to run the above demo follows,008015,022026,030037,044,049,053053N000000N00001026 0001 L068116,105106,110117B101/I9I#071029C029056B026/B001/0991,001/001117I0?0002 ,008015,022029,036040,047054,061068,072/061039 ,00100110400003 000 L003089,040040,040040,04004010400004 000 L003094,040040,040040,04004010400005 000 L003099,040040,040040,04004010400006 11111 L005205)201201,040040,04004010400007 000N/0801MJ29/82MJ32337MU74U24 L030364,338339,343344,35135810400008 M337089MJ32094M0'1S05MS05U!0AS51089 L035399,372379,386393,04004010400009 AS51094CJ35094B431SCJ36S05B379/M089337 L038437,407414,419426,43104010400010 B605MU74U24M337089MJ39094M0'1S05MS05U!0L039476,442449,456463,47004010400011 AS51089AS51094CJ35094B515SCJ36S05B463/ L038514,484491,498503,51004010400012 M089337B605MJ40/82MU99U24B605MV24U24 L036550,522526,533540,54404010400013 B6051M025U24B605/332/,201 L025575,555556,563567,57157210400014 ,2661M0652651M0653302B580 L025600,580581,588589,59659710400015 .601H/80MS47/98MS47/90MJ39S39/332/ L034634,605609,616623,63063410400016 M/90089MU'0S05AS51/90MJ43S14CJ44S05 L035669,642649,656663,04004010400017 B686/MJ45S13B870CJ46S05B709/MJ29S13B870L039708,675682,686693,69870510400018 CJ47S05B732/MJ48S13B870DS05S14CS05S48 L037745,716721,728732,73904010400019 B769/MJ49S13MS48S14B870CJ50S05B870U L035780,751758,765769,77604010400020 CJ51S05B800TAS52S13CJ52S05B819TAS52S13 L038818,788793,800807,81204010400021 CJ53S05B838TAS52S13CCJ50S05B870SB870T L037855,826831,838839,84685110400022 MS47S14MJ36S05NMS14S31AS14S31AS14S31 L036891,863870,871878,88504010400023 AS14S31AS14S31AS14S31AS14S31AS31S31 L035926,899906,913920,04004010400024 MS31S14A/98S14A/98S14AS55S14MS39099 L035961,934941,948955,04004010400025 MS14089MVS4S22MJ32094CSP1S22B'27T L033994,969976,983990,04004010400026 MS05S06SSP1S22DS22S69MS69S22B'34MJ36S06L039'33,'02'09,'16'23,'2704010400027 AJ39094MS062?1AJ56099CJ40/82B'81S L033'66,'41'48,'55'62,04004010400028 MS062?1AJ56099CJ59094B983TAJ56099 L033'99,'74'81,'88'93,04004010400029 CJ40/82B/19SAJ56099M099S39CJ62099B635T2L039/38,/07/12,/19/26,/33/3810400030 CJ40/82B/52S2AS51/98CJ65/98B616T/332 L036/74,/46/51,/52/59,/66/7110400031 /2B00000WCOL:000 L016/90,/76/77,/81/82,/83/8810400032 WROW:000PCHAR:00INDX:111 L024S14,/96/99,S05S06,S07S1210400033 MASK2:00WORK3:000PCOL:000ZERO3 L030S44,S21S23,S29S32,S37S4010400034 0000001100200516 L016S60,S48S49,S52S53,S56S5910400035 0804020101608 L013S73,S63S65,S67S69,S70S7210400036 04020100 L008S81,S76S78,S80040,04004010400037 0000000000000000000000000 L025U24,040040,040040,04004010400038 L025U74,040040,040040,04004010400039 VISITED THE COMPUTER L025U99,040040,040040,04004010400040 HISTORY MUSEUM 00000000000000L039V38,040040,040040,04004010400041 0412040404041414170102030431 L028V66)V39V39,040040,04004010400042 3102040201011402061018310202 L028V94)V67V67,040040,04004010400043 3116300101171406081630171714 L028W22)V95V95,040040,04004010400044 3101020408080814171714171714 L028W50)W23W23,040040,04004010400045 1417171501021200000000001212 L028W78)W51W51,040040,04004010400046 1417171731171730171730171730 L028X06)W79W79,040040,04004010400047 1417161616171424181717171824 L028X34)X07X07,040040,04004010400048 3116163016163131161630161616 L028X62)X35X35,040040,04004010400049 1417162317171517171731171717 L028X90)X63X63,040040,04004010400050 1404040404041400000031000000 L028Y18)X91X91,040040,04004010400051 0702020202181217182224221817 L028Y46)Y19Y19,040040,04004010400052 1616161616163117272121171717 L028Y74)Y47Y47,040040,04004010400053 1717252119171714171717171714 L028Z02)Y75Y75,040040,04004010400054 3017173016161614171717212213 L028Z30)Z03Z03,040040,04004010400055 3017173020181700000000120408 L028Z58)Z31Z31,040040,04004010400056 0001020304160015161614010130 L028Z86)Z59Z59,040040,04004010400057 3104040404040417171717171714 L028!14)Z87Z87,040040,04004010400058 1717171717100417171721212110 L028!42)!15!15,040040,04004010400059 1717100410171717171710040404 L028!70)!43!43,040040,04004010400060 3101020408163114171921251714 L028!98)!71!71,040040,04004010400061 1234567890123456789012345678901000012 L038J36,J29J30,J33J36,04004010400062 00200 ,3.- L011J47,J40J41,J44J45,J46J4710400063 24ZSJA001 L009J56,J49J50,J51J52,J53J5410400064 009132007 L009J65,J60J63,040040,04004010400065 /338080 0066 STEVE WOZNIAK JANUARY 3, 2007 1 2 TEXT BY ROBERT GARNER 1 2 1 2 IBM 1401 1 2 1 2 THE IBM 1401 "DATA PROCESSING SYSTEM", INTRODUCED IN OCTOBER 1959 1 , WAS THE "MODEL-T FORD OF THE COMPUTER INDUSTRY" AND "ONE OF THE 2 MOST IMPORTANT AND SUCCESSFUL PRODUCTS IBM HAD EVER ANNOUNCED." A 1 BOUT 15,000 1401-FAMILY COMPUTERS WERE MANUFACTURED AND DELIVERED 2 WORLDWIDE IN THE 1960'S, FAR EXCEEDING INITIAL EXPECTATIONS. BY M 1 ARCH 1961, AFTER ONLY A SINGLE YEAR OF FULL PRODUCTION, 2,000 2 MACHINES HAD ALREADY BEEN DELIVERED TO CUSTOMERS. BY THE VERY NEX 1 T YEAR, 1962, INCOME FROM THE IBM 1401 SURPASSED OLDER 2 CARD-PUNCH/UNIT-RECORD ACCOUNTING MACHINES FOR THE FIRST TIME. BY 1 1964, 40% OF ALL EXISTENT COMPUTERS WERE 1BM 1401-FAMILY 2 MACHINES. ITS FOLLOW-ON FAMILY COMPATABLE MACHINES, 1410, 1440 AN 1 D 1460, WERE SOLD UNTIL 1970. THE 1400 FAMILY WAS SO SUCCESSFUL 2 THAT IT LED TO THE INDUSTRY'S FIRST PROGRAM-COMPATIBLE COMPUTER C 1 LONE, THE HONEYWELL H-200, OR "LIBERATOR." A RUMORED 1480 WAS 2 DISCONTINUED IN FAVOR OF THE 360/25. 1 2 1 2 THE GOAL OF THE 1401 DESIGN WAS TO OFFER A FLEXIBLE BUSINESS COMP 1 UTER OF AT LEAST THREE TIMES THE SPEED AND AT LOWER COST THAN THE 2 UBIQUITOUS, CARD/UNIT-RECORD, COLLATE/MERGE/PRINT, PLUG-BOARD-BAS 1 ED ACCOUNTING MACHINES OF THE 1950'S (SUCH AS THE IBM 407 AND 2 604). ALTHOUGH OFFERING A GENERAL-PURPOSE COMPUTER WITH PROGRAMMA 1 BLE MAGNETIC-CORE MEMORY WAS A COST RISK, BY CLEVER ARCHITECTURE 2 DESIGN AND USE OF MODERATE-SPEED, ECONOMIC TRANSISTOR CIRCUITS, T 1 HE GOAL WAS ACHIEVED. BY FIRST READING CARD/UNIT-RECORD 2 INFORMATION INTO THE MAIN MEMORY OF THE 1401 BEFORE MANIPULATING 1 IT, COLLATE/MERGE/PRINT OPERATIONS WERE MUCH FASTER THAN ON THE 2 OLD CARD MACHINES. AND THE DATA COULD BE QUICKLY ACCESSED TO/FROM 1 MAGNETIC TAPE FOR STORAGE - MUCH FANTER THAN HANDLING DECKS OF 2 CARDS (WHICH ALSO WORE OUT AND HAD TO BE REJUVENATED VIA DUPLICAT 1 ION). 2 1 2 THE 1401 ARCHITECTURE WAS DESIGNED FOR EFFICIENTLY HANDLING BUSIN 1 ESS DATA-PROCESSING APPLICATIONS. ITS CENTRAL PROCESSING UNIT 2 (CPU) CAN EFFICIENTLY MANIPULATE VARIABLE-LENGTH CHARACTER STRING 1 S AND PERFORM VARIABLE-LENGTH DECIMAL ARITHMETIC (UNLIKE TODAY'S 2 FIXED-WIDTH BINARY ARITHMETIC). FOR INSTANCE, THE CPU CAN OPERATE 1 ON TWO NUMBERS WHERE EACH IS OF AN ARBITRARY LENGTH OR NUMBER OF 2 CHARACTERS. A 1401 CHARACTER IS ENCODED IN 6 BITS, AN END-OF-WORD 1 "WORD MAKE" FLAG BIT, AND A PARITY CHECK BIT. NOTE THAT EVEN 2 THOUGH A CHARACTER WAS 8 BITS WIDE, THE TERM "BYTE" HAD NOT BEEN 1 INVENTED YET. 2 1 2 1401 SYSTEMS COULD BE CONFIGURED WITH 1,400 TO 16,000 CHARACTERS 1 OF MAGNETIC CORE MEMORY (4,000 MIN TYPICAL). MEMORY IS ADDRESSED 2 VIA DECIMAL CHARACTER STRINGS, NOT BINARY DIGITS AS IN NEARLY ALL 1 CONTEMPORARY COMPUTERS. MAGNETIC CORES RETAIN EITHER A "1" OF 2 "0" DEPENDING ON THE CLOCKWISE OR COUNTERCLOCKWISE DIRECTION OF T 1 HE STORED MAGNETIC FIELD. 2 1 2 AN EXALTED FEATURE OF THE 1401 WAS ITS RELIABLE AND ROBUST INPUT/ 1 OUTPUT PERIPHERALS - A LONG IBM TRADITION INCLUDING AN 800-CARD 2 PER MINUTE CARD READER, A 250-CARD-PER-MINUTE CARD PUNCH, A 600-L 1 INE-PER-MINUTE LINE "CHAIN" PRINTER, UP TO SIX REEL-TO-REEL TAPE 2 DRIVES, AND A 20-MILLION-CHARACTER MAGNETIC DISK STORAGE UNIT. TH 1 E SYSTEM AND PERIPHERALS CONTAINED CONSIDERABLE ERROR CHECKING 2 LOGIC. 1 2 1 2 THE 1401 MAY HAVE BEEN EQUIBALENT TO THE MODEL-T IN POPULARITY FO 1 R IBM, BUT WAS FAR MORE COMPLICATED TO MANUFACTURE. WHEREAS THE 2 MODEL-T HAS ABOUT XX COMPONENTS, A LARGE 1401 SYSTEM COMPRISES AB 1 OUT 20,000 MECHANICAL PARTS AND ABOUT 50,000 ELECTRICAL 2 COMPONENTS (10,000 TRANSISTORS AND 14,000 DIODES ON 3,000 CARDS). 1 2 1 2 A TYPICAL, 4K-CHARACTER 1401 SYSTEM RENTED FOR ABOUT $7,000 PER M 1 ONTH IN THE 1960'S, EQUIVALENT TO $42,000 PER MONTH IN TODAY'S 2 DOLLARS (6X DUE TO INFLATION). THIS RENTAL FEE INCLUDED MAINTENAN 1 CE SERVICE AND OPTIONS FEATURES. A TYPICAL 1401 SYSTEM WOULD HAVE 2 COST ABOUT $370,000 IF PURCHASED OUTRIGHT IN 1961 OR $2,240,000 I 1 N TODAY'S DOLLARS. MOST SYSTEMS WERE RENTED, A "CASH COW" FOR 2 IBM. 1 2 1 2 MAIN MEMORY ITSELF WAS VERY EXPENSIVE IN THE 1960'S: ONE 8-BIT CH 1 ARACTER OF 1400 CORE MEMORY IN THE 1960'S COST ABOUT FIVE DOLLARS 2 (OR $30 TODAY). THIS IS 300 MILLION TIMES MORE EXPENSIVE THAT TOD 1 AY'S COST OF MEMORY (ABOUT 0.1 MICRO-DOLLARS PER BYTE). 2 1 2
Sat Jan 20 - generalRon Williams and Bob Erickson came in and added "TLC" to the 077 collator's new clear plastic cover. (see previous Wednesday)
There were frequent visitors to entertain :-))
Wed Jan 24 - generalPresent were Ron Williams, (Bob Erickson was attending to a sick car - head gasket :-((, Allen Palmer, Glen Lea, Ed Thelen.
- After checking with Allison of CHM, we moved the remaining two of our 729 tape drives from in-visible storage back to the 1401 Restoration Room. (They had been parked there for the months that their motors, clutches, bearings and various components had been reworked, restored, rejuvinated, re... )
The reworked, checked 140 pound power supplies were dollied from the work bench area to the 729 area. Allen and Glen started reassembling the tape drives.
- Ed took pictures of previous printouts of the 1402 card reader miss-reads of cards. This was using the 1402 card reads of a deck of all 80 colums of non-printing Group Marks (punches 12-7-8) which yield printing characters of a hole is not read. (12-7 prints as G, 12-8 prints as H, 12 prints as +, 7 prints as 7, 8 prints as 8, 7-8 is no-print).
And with the deck flipped end-for-end, card column 80 read by brush in column 01. Note that misreads shifted to left of printout :-| Or did the right side just get better and we over looked the few errors on the left? (Maybe we indeed did!!)
- Ed Thelen took a long executive lunch (with a former co-worker, male) and when he came back at 3:00, feeling pain, the card reader quit completely, would not pick a card under program control. Ron and Ed looked at the problem briefly, then Ron invited Ed to walk out of the room backward, retracing his arriving steps. Even that did not help. (Since it wasn't Voodoo, there must be a more scientific explaination of the problem.)
- By then it was almost "go home" time - and Allen had still not seen the little present that Ron had prepared for him ;-)) We just gotta have a little fun, and Allen says that he likes Camaraderie. Oh Yes!!
This is the tag which was attached to the new bracket that Ron had made for Allen's magnifier extension lamp. And this is the bracket and mounting plate, made to replace the failed plastic bracket for Allen's portable magnifier lamp. First a little background.
- Ron Williams had made a podium (to hold open schematics) similar to this for himself. Allen admired it so much that Ron made this identical one for Allen. Note the IBM Blue paint.
Note the power strip Allen added to the rear to better connect his magnifier extension lamp and other electric devices. OK - getting ready to fit and mark for drilling And away we go. No sweat :-))
- If you want to do precision work, like having snug holes for screws for no slip
Make sure to use precision methods - so you don't have to rework your work And don't have teasing friends about watching the clock After a great deal of heckling, the project is finished (very properly done). Everything snug and tight - nothing wiggles. People were around to help tease, and admire Now I don't have to feel so embarrased for some late software projects I have heard about.
Thu Jan 25 - Tape Teamand a later e-mailTAU Debug Status - 1/25/07 (Grant and I) Today we continued to troubleshoot intermittent errors in tape operations. Again we erased an entire tape and read it via TAU CE Panel operations. The most common error was still phantom bits occurring on the Read Bus A-bit during the read operations. The TAU indicators were: Error - on A-Reg VRC Error - on R/W Error - on CBA8421 A-Reg 0000000 B-Reg 0000000 R/W-Reg 0010000 The noise bursts were similar to that found last week, but errors were less frequent. The noise was traced back to the skew adjustment Lumped Delay Line Card (BJ__) in the Read pre-amp circuit. The TAU samples the Read Bus only during the "Read Cond" phase of tape operations, but random noise bursts were visible in the 729 even when no tape operations were in progress. For this bit, the delay was jumpered to its minimum. That is, the output jumper wire was connected directly to the card's input pin. Since, other than some circuit loading, the card should not have been participating in the circuit, I removed it. The noise disappeared. We replaced the card with one from the other 729-V drive. No noise. The BJ card contains no active components. Grant gave the card a cursory examination. There were no obvious failed components, but the noise bursts resumed when the card was plugged back into the tape drive. The card is now in the "Bad Cards" box. With the replacement card, we were able to read the entire blank tape without error. We also wrote data records to the entire tape without any read-back errors. (Three bit patterns were used.) When read back, two errors occurred. These were probably at the points where I flipped switches to change the bit pattern. These results are very encouraging. We were unable to run tape system diagnostics due to the broken card reader. Other Tape Drive Problems: The take-up capstan-in switch needs adjustment. High-speed rewind operations require that someone walk over to the drive and tickle the switch to make the drive unload the head. It seems that the switch magnet is too far away and frequently does not detect the capstan being in. Repeated rewinds eventually pop the mercury switch out of its clip on the take-up reel shaft. Other drives have a non-slip rubber tube pressed over the switches glass bulb to prevent it from sliding out of the metal clip. When the mercury switch is out of its clip, rewind operations hang on the transition of high-speed to low-speed. I did not log the above 729 problems, because the logbook for the functional 729 is missing. Allen, do you have it? Other Problems: About eight ceiling fluorescent tubes over the CPU and tape drives are burnt out. It would be a lot easier to see what pins we are probing if they were working. Can we get them replaced? I reported them in December and again today, but follow-up will probably be needed. Regards, Bob
Could be a bad inductor or capacitor. Whatever it is, the noise bursts were intermitent. Bursts occured about every 5 minutes. Maybe the card was tuned into some other noise source in the room. Regards, Bob --- Robert B Garner
wrote: > > These results are very encouraging. > > Yes! > > > The BJ card contains no active components. > > What the heck does it do then? (Like "junk DNA?" > ;-) > Perhaps problem is a bad cap? > (We've also had faulty inductors...) > > - Robert
Comment by Ed Thelen (Ron Williams does not do e-mail)How interesting !!! The misreads by the 1402 are also bursty, like non-random noise,
Sat Jan 27 - 4th Sat
Present were: Ron Williams, Tim Coslett, and visited Ron Crane (hello) Jeff
- 1402 Card Reader didn't work when startup, then started working -
- Card Feed problem disappeared, bad contact??
- Harlan Snyder showed up to visit, he got very ill last August - still looks a bit frail.
- Tim fixed cards -
- Bob Erickson was AWOL, son visiting from Tahoe
- Then will be cruising for a month or so.
- Both key punches down:
- - the Morgan Hill key board locks up - feed, register, punch one key, then lock.
- - Selam's needs card guide, you must hand feed each card
Maybe Frank King, Glen Lea can get one or more working soon
- - very inconvenient having no effective keypunch
- A divide problem cropped up as they left.
Wed Jan 31 - general
Present were: Ron Williams, Bob Erickson, Frank King, Bill Flora, Allen Palmer, Chuck Kantmann, Robert Garner, Ed Thelen
- Ron Williams and Bill Flora scratched heads trying to figure why the card reader - two feed cycles instead of three cycles - Bill has seen it happen also -
- Bill and Frank chased the 1402 card reader motor time out problem, The motors run all day.
- Allen Palmer - worked hard in his corner.
- Bob Erickson - both keypunches now work, one was operator error - auto duplic cockpit error, the
- Demos for visitors
- On the test line - final test was an actual CAP Test - essentially payr DFT TEST - particular function - about a whole box, Ripple Read is half a box.
- Space Suppress - 6 line/8 line/neutral - print blanks, until fault - - radio - scope, trigger on op-code - don't even have to trigger -
- Smart book - test decks for particular gates when margining
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