Saturday, July 18, 2015

Completing the Set

Between 1997 and 2002, I collected well over a hundred Commodore computers, and dozens of disk drives, printers, monitors, modems, and other accessories.  By the time I stopped, my "Wanted" list had shrunk to almost nothing, and many of the things on it where only unicorn-like objects of rumor.

One of those computers was the Commodore 264, the namesake model of the "264 Series".  A set of computers based around the MOS 7360 "TED" chip, which grants the series the sometimes moniker of "TED Machines".  This series includes the Commodore 116, Commodore 16, Commodore 232, Commodore 264, Commodore Plus/4, and Commodore V364.

Luck and circumstance allowed me to find every machine on the list above, except one: The Commodore 264.  All my searching had only revealed one other owner, and while he was not selling, I did secure a promise that I would get first right of refusal when he does. :)

Thirteen years later, you'd think I'd have forgotten about it.  But a mindlessly OCD collector never forgets, and I finally struck gold on eBay:


This unit left the Commodore U.S. offices for a game company called Infocom, where it played some role in the porting of their famous Zork trilogy to the Plus/4.  A few years later, a fellow from Rhode Island was granted a tour of Infocom, his favorite game company.  He was given this computer, which the company no longer needed, as a gift.  After deciding it was not interesting, it went into storage until the owner decided the storage was a bit too full, and some of it needed to go.  So to eBay went this computer, and finally to my Commodore lab.



After taking it from the box, the first thing I noticed was that it needed a good cleaning, but that it was in remarkably good cosmetic condition.  An external inspection revealed that it did indeed share its case design with the Plus/4, with the exception that the power connector was an old round C64-style DIN connector, instead of the square custom connector common on the Plus/4s.



The case was held closed by some clear tape, which had long rotted away.  There were no screws holding the case together.  I would later surmise, when I put screws in, that it had probably never been screwed shut, like, ever.

After a quick visual inspection of the board, I decided that it was probably safe to attempt to turn it on.  I used a nearby C64c power supply and attempted to give it life.  Upon flipping the switch, the computer perfectly synced with my NTSC monitor, which wasn't surprising given its origin, but still gave me some relief.  The familiar 264 series color screen popped up, and BASIC appeared to initialize by placing its familiar message at the top of the screen.  Under that message was the READY prompt, but under that was a crash message and an immediate drop into the computers built-in machine language monitor.



I filed this information away, powered it down, and planned a more detailed inspection of the board itself.  While that was going on, the space bar and the four directional arrow key heads would be carefully removed for retr0brighting, since they showed signs of yellowing.

During my first board inspection, I noticed that the keyboard cable was not even connected to the board (the owner had been considerate enough to warn me about this), and several of the keyboard cable pens were bent up.  A light application of Superglue under the folded pins corrected this problem, so I turned my attention to the board itself:




Several interesting things popped out at me:

  • Every single IC is socketed! Repair will be simple when the time comes!
  • The TED chip (located upper-middle, in that square casing) had no protection from overheating, which, in the Plus/4, was provided by a metal contact that dips down inside the lid which covers that casing area, along with a dab of heat sink compound.  
  • The RF modulator, silver box in the upper-left, has "No 20" written on it.  Perhaps this was 264 board number 20?  Prototypes rarely had serial numbers, so I guess they needed to keep track somehow.
  • The KERNAL and BASIC ROM chips (bottom left, just to the left of those empty sockets) are, of course, only dated EPROMs.  They were still a work-in-progress at the time this unit was delivered.
  • The board assembly number is the same used in the Plus/4. No difference there at all.  And the empty sockets in the middle are already there, ready to receive the built-in software ROMs that given the Plus/4 its name.
  • The PLA chip (marked 1CCD), is also some sort of pre-production chip.
My next step would be to archive the KERNAL and BASIC ROM chips, which would also reveal which of the two, if either, caused the crash I observed during my initial test.





During removal of the BASIC ROM, I immediately saw a problem: pin 1 on the chip was bent up, and was either not making contact with the socket, or was making intermittent contact.  After removing the chip, I carefully bent it back into shape.

For reading in ROMs, I still use a Promenade C1 EPROM programmer on my Commodore 64c.  For software, I either use PROMOS 2.0 shell, or PROMSHELL 2.0, depending on the type of ROM that needs reading.  I had no trouble reading either chip, and saved them onto a 1581 3.5" floppy, for transfer to my PC and later uploading.

The ROMs were marked 1/19, which I surmised to refer to the snapshot date of the software on them, probably January 19th, 1984, which would be 3-4 months before release.

Comparing them with the ROMs from Jim Brain's Commodore 264 (marked 2/3) revealed that there are differences, though determining what they are and their significance will have to wait.

So, with my internal inspection and archiving done, and all the photographs taken, I carefully re-inserted the newly fixed keyboard cable, and re-connected the case.  Since it had previously been held together with tape, I scavenged some case screws from an old Plus/4 that was missing it's 7501 CPU altogether and used those to button it up properly.  The screws went in snugly, making me think that the case had never been screwed shut in its entire life.

Another power-on test showed that the bent pin on the BASIC ROM was, in the end, the only problem.  The computer was fully operational.  Further tinkering will wait until the differences in the BASIC and KERNAL ROMs are identified, so that I know what there is to tinker with.

Until then, I can bask in the satisfaction of having completed the 264 Series in my Commodore collection, and look forward to whatever secrets it may reveal in the future.





2 comments:

  1. For posterity, as of this date, there are 139 home computers in the collection, representing 101 different models of Commodore products. I didn't count the drives, printers, monitors, etc.

    ReplyDelete
  2. Do you know of any other true 264's? (besides the one in my basement)

    ReplyDelete