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For sale :: IMSAI 8080

OK, first, they don't seem to know what the front panel switches do. Next the RAM card is not likely a 64k static card. Maybe a 64k dynamic but the chips don't have enough leads to support that much of the address space.
The card called a single board computer is likely an I/O card with chips like Z80-SIO and such.
It does look like a nice IMSAI though.
Dwight
 
Dwight Elvey said:
OK, first, they don't seem to know what the front panel switches do. Next the RAM card is not likely a 64k static card. Maybe a 64k dynamic but the chips don't have enough leads to support that much of the address space.
The card called a single board computer is likely an I/O card with chips like Z80-SIO and such.
It does look like a nice IMSAI though.
Dwight
Click to expand...

I take it back, it is a Z80 SBC card, by SD systems.
See:
http://www.s100computers.com/Hardware Folder/SD Systems/SBC/SD Systems SBC.htm
Dwight
 
The math for the RAM card, assuming it was static RAM.
8 columns, 64k/8 = 8k per column.
8K requires 13 address lines.
16 pin parts also need a data I/O, chip select, rd/wr, power and ground.
16 - 5 = 11
I need more pins or more chips.
Dwight
 
Dwight Elvey said:
The math for the RAM card, assuming it was static RAM.
8 columns, 64k/8 = 8k per column.
8K requires 13 address lines.
16 pin parts also need a data I/O, chip select, rd/wr, power and ground.
16 - 5 = 11
I need more pins or more chips.
Dwight
Click to expand...

From the top view they gave us, it appeared to be an vanilla 8K RAM board to me, but I can't really tell.

The surprising thing for me - going along with the thought of "do they know what they're doing?" - was that second processor board (the one they called an SBC) also plugged in along with the IMSAI CPU when they were playing with the front panel? If so, I guess there's pretty much why some of the FP light patterns seemed to be odd. I've never tried to run an S-100 system with two processors in it at the same time - both fighting to be the primary CPU.

SIGH.

smp
 
IMSAI 8080 microcomputer serial number 003669. Powers on, all switches appear to work.
IMSAI CPU board http://www.s100computers.com/Hardware Folder/IMSAI/8080 CPU/8080.htm

Seals Electronics Static RAM Board http://www.s100computers.com/Hardware Folder/Seals Electronics/8K RAM/8K Static RAM.htm
64 socketed AM91L02APC 1k x 1 static RAM

SD SYSTEMS Versafloppy II (rev P) http://www.s100computers.com/Hardware Folder/SD Systems/VersaFloppy/SD Systems Versafloppy.htm
No floppy disk drives

SD SYSTEMS SBC (Single Board Computer) S-100 card http://www.s100computers.com/Hardware Folder/SD Systems/SBC/SD Systems SBC.htm
I assume this was used in place of the IMSAI CPU.
 
Pepta said:
I was thinking $2500 or best offer.
Click to expand...

That's the high end of reasonable, it does look like it's pretty clean and is at least shown to not have smoked when you powered it up! The SD Systems SBC-100 or SBC-200 is curious, that's not a board that is designed to operate with another CPU card in the system, and it looks like this machine does have the IMSAI CPU board.

You might (gently and carefully) pull the cards and photograph them, so folks can determine for sure what's in there.
 
smp said:
From the top view they gave us, it appeared to be an vanilla 8K RAM board to me, but I can't really tell.

The surprising thing for me - going along with the thought of "do they know what they're doing?" - was that second processor board (the one they called an SBC) also plugged in along with the IMSAI CPU when they were playing with the front panel? If so, I guess there's pretty much why some of the FP light patterns seemed to be odd. I've never tried to run an S-100 system with two processors in it at the same time - both fighting to be the primary CPU.

SIGH.

smp
Click to expand...

I know that CompuPro had an 8085/8088 board that you could switch between them using an I/O port. Also, the S100 Computers "new" boards have several processor versions that can co-exist, again, using a port address to switch between the boards. But, only one CPU was operating at a time.

Rich
 
Very clean machine. Cosmetically looks to be in great shape. Probably doesn't come with mud wasp nests, like mine did. The MPU card may be early, judging from the size of the crystal and white ceramic CPU. Fun to toggle in the front panel, but will take some work to get serial and disks running.

Why not pop out the disk interface and SBC and toggle in some small programs?

Here's a simple counting program at 0000:

16 FF 7A D3 FF 01 FF FF 0B 78 B1 C2 08 00 15 C3 02 00
 
smp said:
That fits right in with the normally seen eBay prices. You should put up your auction and post a link to it here.

smp
Click to expand...

Is it though? I see them listed but I never see them sell. It's also likely that the one we see listed now is the same one we always see.

It looks nice to me and its nice to see it working, I'm just not clear how you know what the going rate is on these unless there are completed "sales" to reference.
 
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