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View Full Version : Untouched Altair 8800 rev0 kit. What next?



edcross
August 7th, 2018, 06:04 AM
Dear forum, I got hands on this Altair 8800 rev0 kit in pretty good shape that appears to never have seen the light of actual usage. The system features the default base pcb with just two populated slots including the cpu card and 1k card with 512bytes of ram.

Despite the obvious use case limitations I love the system as is and I feel it shouldn't be expanded. That said I miss be able to experience and demo usage beyond front panel operation.

Is there any known card I could use to switch the 1K memory card with something more advanced combining IO + enough ram to at least get to run Basic? Any other out of the box ideas? eg bus riser card?

Look forward to your thoughts and ideas.

47166
47167

smp
August 7th, 2018, 07:04 AM
Excellent! I'd love to get my hands on one like that!

I suggest the JAIR-8080:

http://www.s100computers.com/My%20System%20Pages/8080%20CPU%20Board/8080%20CPU%20Board.htm

It's an all-on-one-board system where you can enable or disable RAM, ROM, SIO, etc for mixing and matching or testing other boards in your system. Best of all it has a nice multiple floppy disk emulator on the SD card.

You can see these for sale occasionally on eBay by the designer. You can also contact the designer on the Altair Computer Club Yahoo Group:

https://groups.yahoo.com/neo/groups/altaircomputerclub/conversations/messages

His name is Josh Bensadon, he's active, and he's very helpful.

Good luck!

smp

edcross
August 7th, 2018, 08:24 AM
That looks like a great piece of hardware, the fact that you can disable specific features is just fantastic. Thanks so much for sharing!

monahan_z
August 7th, 2018, 10:01 AM
Or see if you can get your hands on an old TDL SMB. Can run TDL basic from cassette!
John

deramp5113
August 7th, 2018, 07:56 PM
If you want to run original Altair Software, you’ll want to get an Altair 88-2SIO board or equivalent for the serial ports. The actual 2SIO is fairly hard to find and expensive. A Solid State Music (SSM) IO4 board can be strapped to look like a 2SIO board as far as most Altair software is concerned. Martin Eberhard’s 88-2SIOJP is a great drop-in (and enhanced) replacement for the 88-2SIO. See it at http://deramp.com/2SIOJP.html.

Unfortunately, none of these boards include RAM. You could solder in two new edge connectors and add a RAM board, or a board like the Altair FDC+ (to give you RAM and let you run Altair disk software). I believe Martin has some of the Sullins connectors that fit the original Altair motherboards.

Mike

Marty
August 9th, 2018, 02:35 PM
Hi All;

If you are at the right place and the right time, sometimes You can find a 16K or 32K or 64K Ram Board, on Ebay, or maybe someone on one of the Forums might have something that they would be willing to Sell to You..

Get connected with the various S-100 groups and start asking for things that You need to make it into a System that is to Your Liking..

And above all Read Everything You can get Your hands on about the S-100 (Altair) Buss.. Local Library and such..

THANK YOU Marty

MarsMan2020
August 10th, 2018, 10:28 AM
That looks like a great piece of hardware, the fact that you can disable specific features is just fantastic. Thanks so much for sharing!

The JAIR8080 is a great board, Josh put a lot of time into the design. I just built one to help with debugging an Altair that I acquired.

However as mentioned above, the serial and parallel ports are not directly compatible with unmodified MITS software. Thankfully the JAIR design makes it relatively easy to only use what you need from the board.

If you want to stick with the two slots on the backplane, you could run a JAIR8080 for CPU+RAM+ROM in one slot, and the 88-2SIOJP that Mike mentions in the 2nd slot for serial I/O (or use the JAIR8080 for CPU+RAM, and use the ROM features on the 88-2SIOJP). I think that be the easiest path to run MITS software like BASIC that uses the 88-2SIO without modifying the backplane.

Also - if your backplane is the Rev 0 that is only 0.063" thick, be careful when installing/removing cards. My understanding is that MITS doubled the thickness on later revisions of the 4-slot backplanes to .125" based on the thin design breaking in some instances.

Chuck(G)
August 10th, 2018, 12:01 PM
Does the JAR8080 work with the 8800 front panel?

32K was really out of the range of the Rev0 board set--back in the day that this was new, you couldn't fit that much RAM into the system. I thought I was doing okay with 2 4K DRAM boards (terrible things!).

What might be period-correct would be an 8K SRAM board (using 64 21L02/91L02 chips), an SIO A board or two, and the CPU. That's your 4-board set, which is about all the original Rev0 power supply could handle. If you had an ASR TTY or KC audio tape adapter, that would be enough to run BASIC or even the Processor Technology monitor/editor/assembler.

MarsMan2020
August 10th, 2018, 12:38 PM
Does the JAR8080 work with the 8800 front panel?

Yes, it has locations for both the Altair and IMSAI front panel connectors.

glitch
August 10th, 2018, 01:02 PM
The JAIR8080 is an excellent option, especially since you won't have to modify your system at all.

I've put together some custom boards to keep rev 0 machines in as-is states in the past: usually wire wrap or point-to-point wired, with 32K RAM, some amount of ROM, and a serial port that implements one channel of the 88-2SIO. I've never laid it out as an actual circuit board though; I probably should at some point.

MarsMan2020
August 10th, 2018, 04:09 PM
The JAIR8080 is an excellent option, especially since you won't have to modify your system at all.

I've put together some custom boards to keep rev 0 machines in as-is states in the past: usually wire wrap or point-to-point wired, with 32K RAM, some amount of ROM, and a serial port that implements one channel of the 88-2SIO. I've never laid it out as an actual circuit board though; I probably should at some point.

I'm about to start working on a board to go with my Altair with 1/4 of an 88-4PIO and an 88-ACR compatible modem section, since my chassis came with cabling for the both of those but not the cards. I have a hard time keeping wire wrapped and point to point boards neat and tidy enough so I'm going to go ahead and get PCBs made.

Perhaps instead I should do:
-1/4 of a 4PIO
-88-ACR compatible modem (still researching different ways to implement the modem)
-1/2 of an 88-2SIO
-32-64KB of RAM and 16K ROM

This could be used to either provide 'MITS Compatible' I/O to a JAIR board (leaving the RAM and ROM unpopulated), or on its own with a MITS 8080 board as a 2-board solution.