Technology and retro computer blog

Altair 8800 S100 boards

MITS 8800 CPU board - the cpu card works fine but on close inspection assembly is very rough.  Many of the traces have been re-soldered, and it looks like quite a few hacks have been done to this card.  The traces are prone to blackening.  And at one stage the machine wasn't working properly, it wouldn't respond to the front panel when turned on.  On removing the cpu card I noticed that the contacts on the card's edge connector were very blackened, so I lightly rubbed them with some steel wool, (not recommended, use an eraser instead).  This fixed the responsiveness problem.  Obviously the contacts weren't making a very good connection.  A simple fix which I was pretty happy with.  This particular cpu board has an Intel 8080A processor installed, date on the chip is 1974.


California Computer Systems 64k dynamic ram board - since getting the Altair  I've purchased a couple of memory cards, the first was a TDL16k which unfortunately had stuck bits.  I also purchased this CCS 64k which seems to be ok.  Being a 64k card it provides the Altair the maximum amount of memory.  It's also a fairly late s100 card dated 1980.  There's a set of bank select jumpers in the top left corner which allows any 16k block of memory to be disabled.  I've tested the CCS64k using the Altair Rom monitor by John Garza and it gives it a clean bill of health.


Cromemco 8k Bytesaver - The 8k Bytesaver is an 8k prom card that can read and write 2708 eproms.  It has capacity for eight 2708 eprom chips (1k each).  These cards were developed by Cromemco primarily for use in an Altair.  I have two 8k Bytesavers that I can use in my Altair.  The 8k Bytesaver has enough capacity to store 8k Basic on seven eproms and still have enough space to store a 1k monitor program for loading software and examining memory.  I've also created socket adapters for using more modern 2716 eproms and 2816 eeproms with the Bytesaver (see post).  Using the Bytesaver I can load 8k Basic into the Altair with a few switches after power up.


Solid State Music IO4 - the serial card in the Altair is an SSMIO4.  This is a very rare s100 serial card because it can be configured for use in different s100 machines.  Importantly for the Altair it can be configured exactly like the MITS 88-2SIO to run MITS software.  See my guide about configuring the SSM IO4 for the Altair.


MITS 88-S4K memory card - I have two of the MITS 88-S4K cards.  One seems to work fine, but the other is a little flakey.  I've managed to do a simple memory test on both cards using the Bytemover program.  The Bytemover program moves a 1k chunk of memory from any 1k location withing an 8k boundary.  Using this you can copy the program from one 1k chunk to another and then run that copy.  If the copy moves the memory successfully it's a good test of the memory in that location.


MITS 88-2SIO Serial Card - the MITS 88-2SIO pictured above is configured for RS232 serial interfacing.  The wirewrap hack that you see on the left, sets serial ports 0 and 1 to addresses 20 and 22 (octal).  This is the standard terminal I/O address for 88-2SIO to use MITS software like Basic.


MITS disk board 1 rev. 0 X3 - this is one of the two boards that makes up the MITS floppy disk controller.


MITS disk board 2 rev. 0 X2 - this is the other board in the disk controller set


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