Reproduction 8080A CPU boards for the IMSAI and Altair are now available for shipping

[gekaufman]

Reproduction 8080A CPU boards for the IMSAI and Altair are now available for shipping.

Glitch is also planning to offer parts kits for both boards.

First, a special thanks to the generous assistance of Santo Nucifora (who loaned me a blank Altair 8800 CPU board) Glitch (who cleaned up gerber files and built up the IMSAI prototype, and Martin Eberhard (who built up the Altair Prototype).

I arranged to have an original Altair 8800CPU Revision 1 and IMSAI MPU-A Rev-4 CPU boards scanned to Gerber files thru Gardien Services.

My goal in this project was to make available a close replica of the original boards. The reproductions are true to the original design and can be constructed using the original manuals (available on the www.s100computer.com site and other locations).


The boards are a very close copy of the vintage board and have been produced with hard gold plating on the fingers and a matte green finish that is similar to the original board. A small mark has been placed on the rear of each to indicate they are a reproduction so they are not passed off as an original in the future.

Here is the original Imsai CPU board that was scanned:

A writeup by Glitch of his prototype testing is here:

http://www.vcfed.org/forum/showthread.php?62636-Gary-Kaufman-s-IMSAI-MPU-A-Reproduction-Board

And the reproduction board is here

Full sized images are at:

http://www.the-planet.org/gkaufman/S100/Imsai/Repro_Front.jpg
http://www.the-planet.org/gkaufman/S100/Imsai/Repro_Rear.jpg


The prototype of the Altair 8800CPU board is here:

And the reproduction board is here:

Full sized images are at:

http://www.the-planet.org/gkaufman/S100/Altair/Repro_Front.jpg

http://www.the-planet.org/gkaufman/S100/Altair/Repro_Rear.jpg

The cost of the scanning was significant, and added to the cost of the boards.

Either IMSAI or Altair boards (Bare) are $30 each, shipping in the USA is $6.70 priority mail for any number of boards.

Payment is by paypal to gkaufman@the-planet.org
Please use the friends/family option or add 4% to cover paypal fees.
Please email me your shipping address (it is not sent automatically by Paypal with the friends/family option).
I'm also happy to take a personal check, please email or pm for my mailing address.
I should be able to ship within a day or two in most cases, and priority mail is 2-3 days to most locations.

I'm happy to ship to non-USA destinations, please email me directly for postal costs, or look on the USPS website. Postage is at my actual cost.

BTW, I also have spare 4mb SRAM boards and 8086 CPU boards still available, $15 each.

Thanks!

- Gary

 

[Chuck(G)]

Nice work, Gary, but I notice a few differences between a "real" 8800 CPU board your duplicate.

The "real" ones are not solder-masked-they were bare boards with tinned traces. Also, the front-panel Molex connector uses round, not square pins. I'm sure there are other minor differences, such as use of film resistors instead of composition, but I'm working from memory.

Were these departures mostly due to available parts and production facilities?

 

[gekaufman]

Chuck -

I started with an Altair 8800 "Revision 1" board. The Revision 1 corrected the incorrect Molex connector spacing on the original run. This board did have a solder mask and gold plating on the connector, so the appearance is actually surprisingly true to the original. The holes will accommodate round or square pins. I'm only providing bare boards, the choice of resistors etc would be up to the builder.

If desired it would be fairly easy for me to arrange a run without solder mask or gold plating on the connector that would closely mirror the earlier revision.

Hopefully it will be a fun retro project for folks (like me) who missed out on an original Altair.

 

[Chuck(G)]

Gary, thanks for the explanation!

I'll confess to having only the Rev. 0 CPU board, so I was working from that. I can't say that I had fun assembling it on my kitchen table back in the day; I recall doing a fair amount of grumbling about the cheap white stranded wire, however.

Exactly what was the issue with the Rev. 0 Molex connector spacing? I don't recall having difficulties there.

 

[gekaufman]

Exactly what was the issue with the Rev. 0 Molex connector spacing? I don't recall having difficulties there.

My understanding is that they used .15 instead of .156 spacing - and you had to cut the 8 pin connector in half to "encourage" it to fit into the PC board.

That said, I don't own a "real" Altair. Perhaps someone with first hand experience can add information.

A poor student at the time - my first CP/M experience was with Digital Research's "Big Board". My Imsai came a bit later

- Gary

 

[Chuck(G)]

Nope, I don't recall that connector business at all. And when I got a Z80 card to take the place of the 8080 one, I used a standard 0.156" spacing female Molex and a DIP plugin header to make an adapter. I think I still have the thing.

Only a few things stick out in my memory about my Altair (still have it, sitting on a shelf for decades):

1. The terrible white hookup wire that would break if flexed more than a couple of times.
2. The horrible 4K DRAM boards that would change data when you hit the "reset" switch
3. The traces on the front panel carrying one side of the AC line (note that there is no solder mask, so watch what you touch!
4. The poor quality of the power supply. I'm certain that the filter caps on mine have dried out long ago.
5. What it seemed to me was a gratuitous inclusion of a 74L00 on the front panel just so a circuit could be wire-ORed.

Still, it was a great toy, but had it been available, I would have gladly shelled out for the better-constructed IMSAI box.