Schedule May 2009

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Wed May 6 - General, Thurs May 7 - Tape Team
Wed May 13 - General, Thurs May 14 - Tape Team, Sat May 11 - 2nd Sat
Wed May 20 - General, Thurs May 21 - Tape Team, Sat May 23 - 4th Sat
Wed May 27 - General, Thurs May 28 - Tape Team,

Wed May 06 - general

Thursday May 07 - Tape Team


Wednesday May 06 - General

Thursday May 09 - Tape Team


Saturday May 16 - 2nd Saturday

Wednesday May 13 - General

Thursday May 14 - Tape Team

Wednesday May 20 - General

Thursday May 21 - Tape Team

TAU Debug Status - 5/21/09

I installed a new Emulator kernel driver that had some improved checking of messages coming from the Adapter (PIC). I suspected that the Windows "Blue Screen" crashes were being caused by an unexpected message. My suspicion was correct. The failing sequence was...
  • The 1401 TAU writes a record to the Emulator Adapter. The Adapter buffers the record and transmits a Upload Request Event to the Webserver/driver.
  • Before the Webserver responds, the 1401 TAU glitches the Select line in the tape interface. The glitch is caused by a second tape operation being directed to the same drive. The type of latch used in the TAU is reset a half cycle before it is set again.
  • The glitch is detected by the Adapter and it records that it is no longer selected.
  • The Upload Data command from the Webserver is received while the Adapter is deselected and it responds to the Webserver that the Upload was command was being requested from a non-selected drive, resulting in an error condition.
The glitch window was very small, which matches the rarity of the occurrence of this error. The proposed fix is...
  • Patch the driver to detect and log this occurrence rather than crash, if/when it occurs. This fix has been made and verified.
  • Modify the adapter firmware to tag the data to be uploaded with the drive to which it was directed. Then when the Upload Command is received, check this tag rather than the current select status. This fix is planned to be installed next week.
Jeff, I need the ICD2 to load the new firmware. Can you bring it to the shop on Monday?


Saturday May 23 - 4th Saturday

Ed Thelen was having another adventure. He had complained Monday to his doctor about his left foot dragging.

Wednesday May 27 - General

  • Present were: Ron Williams, Bob Erickson Bill Flora, Glenn Lea, Don Luke, George Ahearn, Judith Haemmerle, Joe Preston, Stan Paddock, Bill Newman, LaFarr Stuart, Ed Thelen, Robert Garner.

  • Bill Newman is getting used to the unusual logic of the SMS cards in the 1401. "Complemented Transistor Diode Logic (CTDL)" Both PNP and NPN transistors are used as logic elements. The result is unusual, there are two voltage levels for TRUE or "1" and two different voltage levels for FALSE or "0", depending upon the output circuit type. From IBM Standard Modular System page 15

  • People asked George Ahearn (who helped design/implement the 1401) if he had troubles locating the correct circuit type. He said that they sometimes asked/begged for some particular circuit to be added to the SMS system - but there was great reluctance by IBM to add even more SMS card types - the 1401 uses more than 100 SMS card types.

  • LaFarr Stuart came for a visit - and told many applications of 4 K card only (no tapes) 1401s , including a billing application for Las Vegas Telephone that used all 5 hoppers in the 1402 Card Reader Punch. A "cash card" that was mailed in the bill went to the middle pocket.

  • Bill Flora discovered a/the reason the joggler for the middle pocket of the CT 1402 was not working - The spring clutch was deformed because the two parts of the central shaft had separated and the middle of the spring dropped into the gap.
    One half of the clutch shaft - the gap between this and the other half had opened. two halves together

  • Damaged clutch springs Left is a broken spring, the one nearest the penny is from newly found spares.

  • Judith started searching the Intenet for spare clutches and/or springs. Believe-or-not she found a guy with parts who knew they were for a 1402 - and said that there was little call for them since a burst of activity for "Y2K" - figure the chances of that?

  • This is the completed assembly, a spare clutch spring is in the front.
    If you don't understand the clutches completely, join the crowd ;-))

  • Jim Somers presented this card to me - signed by my friends at CHM

  • LaFarr saw the Babbage Demo :-)) and took the Visible Storage tour. :=)) About 4:00 he chauffeured Ed home - the surgeon said Ed should not drive for a month. As we left, Stan ( a wanna-be markeeteer?? ) had 3 of us point a random places where Bill Newman was troubleshooting some esoteric "Edit" instruction bug - we should have had a stylish model !!

Thursday May 28 - Tape Team

Autocoder Debug Status - 5/28/09 (Allen P., Ron W., & me)
  • Loaded the new firmware into the 729 Emulator. The new firmware was supposed to fix a timing issue that caused intermittent errors.
  • Ran the 4 Tape Autocoder Program (actually 5 tapes, the 5th tape is for the optional listing file). To execute properly, the 729 Emulator must emulate FIVE 729 tape drives.
  • Intermittent errors occurred on the first two attempts. The symptom seemed to be the TAU not dropping GO between tape operations.
  • After lunch the intermittent errors disappeared.
  • Autocoder ran. It detected 8 errors in the source program.
    #1 - missing JOB card (it was missing)
    #2 - missing CTL card (it was missing)
    #3-8 - lack of two spaces separating the operand from the comment on cards
    Note that the cross-assembler does not enforce these errors. The 1401 Autocoder seemed to generate correct output also, even though it complained about the errors.
  • Made fixes to the program source file. (Also: Autocoder requires that every input record to be 80 characters in length, even if it is read from tape.)
  • Autocoder ran successfully, indicating no errors!
  • We ran Autocoder four times without any failures.

From Sam Sjogren

Actually, the current version of the cross-assembler does enforce the rule about two spaces (at least two) being required between operand and comments. When I was modifying the tape copy program on the emulator to use different virtual tape drives to try and work around the timing issue we had around the time of Chris Holloway's visit I had to insert spaces on some lines to get rid of the error messages.


From Robert Garner

I am delighted to report that, remarkably, after much work over the past 20 months, in addition to helping to bring up the (operational) tape subsystems on both 1401s, Bob Feretich and his Thursday tape crew have succeeded in running a 5-tape Autocoder on the German 1401 via his ["729 Tape Drive Emulator"], (which employs about 20k lines of code)!

The Autocoder image that is running is the very one that Paul Pierce recovered for us from the 7-track Autocoder source tape we procured with the Connecticut 1401 system last year!

This capability makes it possible to hold classes which involve students learning computer architecture and writing programs that run on our restored 1401(s).

Congratulations tape and 1401 restoration team!

- Robert

Robert Garner [RG] responding to Grant Saviers [GS]

[GS] The whole team should celebrate! (unfortunately, I'm out of town next week)

[RG] Per our previous email exchange, are you still willing to hold a 1401 get together/celebration at your place? Any thoughts on which Weds? THANKS!

[GS] Thus, for me, successfully running Autocoder is the first time we have proof that the DE 1401 really works.

[RG] Autocoder is indeed a great test! (Some time ago we ran most of the diagnostics (although I'm not sure how good they really are.)

[RG] We'll have to hook the "729 Emulator" (i prefer that name over "TAU analyzer") to the CT 1401 now!

[GS] For a computer, I never believe "it works" until the O/S loads and a big Fortran program compiles.

[RG] I'll bet you Bob will try the Fortran compiler next! ;-)

[Ed Thelen comments] Oddly, there is a card only version of 1401 FORTRAN. LaFarr says you fill the 1402 card reader tray with the remaining 62 passes (after the first pass and the FORTRAN source deck) and let the machine go to work. The CPC assembler can also work in a card only 4 K 1401 :-))

[RG] You'll be waiting a long time for that OS to run... (Although Alan Kay told me he wrote a simple spooling OS for the 1401. Did you see the emails with Brooks et al, that it looks like IBM's first OS may have been released on the 1410?)

- Robert

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