Altair8800 'kit' - can you identify this stuff?

From: Dwight K. Elvey <>
Date: Thu Jan 27 13:09:20 2005

>From: "William Layer" <>
>Display / Control board (rev 1) removed, and showing evidence of a burnout in
the lower left, 7400 chip I think. Someone has socketed every chip on the board,
with a collection of random colorful sockets. The board shows some small rework
with kynar, to fix lost pads/traces on one socket pattern. Needs a couple of
switches replaced. Marked "3421K" in black Sharpie.

 Get a schematic and start plaing with it. Like the IMSAI panel,
it uses the processor to actually generate the addresses and
fetching from the bus. You should check for shorts with an
ohm meter before powering up. After powering up, check for anything
that is hot. These old TTL parts would run slightly warm but
should not be hot. Be ready to remove the power quickly in case
of smoke. With power applied, even FR4 will burn if sustained
with an electrical arc.
 There is a schematic and layout on that CD ROM that has many
of the schematics and such ( I've seen but don't have it my self ).

>8080 CPU card (rev 1) removed and showing signs of modification (a mystery chip
has been added with glue & kynar), and CPU is missing. Marked "3423K" in black

 The extra chip is most likely to generate the correct status signals
for the refresh of the dynamic RAM. The early boards were designed
around static RAM systems and it wasn't until later that the status
signals were added. The earlier DRAM boards had no standard way of
providing these signals so there are several different ways this
was done.

>A card marked "MCT R30 ASSY 105510" (seems like serial or parallel I/O)

 List major IC's?
>A card marked "SD Systems VersaFloppy II" (must be the disk controller)

 Will most likely only work with the Z80 processor board. The 8080 was
a little on the slow side to handle the disk transfers. Most 8080 systems
used a DMA interface for disk drives. I did look at some tricky software
that I believe would have worked on a 8080 but it required transfering
4 bytes at a time. It has been some time since I looked at doing that
so I'm not much help now. I think the main thing was that after the
controller gave the status, you had something like 13 uSec to read
the data or it was lost.

>A card marked "SD Systems Expandoram II" (must be the memory card, and it's
fully populated. No idea what the capacity is)

 It depends on which chips are there. If it has the four banks of 16K
chips, you have 64K. It could also be populated with 18K or 4K
chips but that is unlikely as it came out just when the 16K chips
were getting available. See my note above about the refresh signals.

>A card marked "SD Systems SBC-200" (has a Z-80A cpu, and what I think is the
matching Z-80 buss driver chip. Has 4 ROM sockets, two of which are populated.
One is clearly marked 'EDO BIOS'. Also has edge connectors marked serial &
parallel I/O. Seems like a multifunction card; CPU, ROM & I/O)

 This is most likely the main processor that was used with the system
for CP/M.

>A card marked "Signum Systems MICE-48" with a long ribbon cable leading to an
emulator probe, bearing an EPROM chip. (It's clearly an In-Circuit Emulator
device, my guess is that it was emulating an 8048 or similar)

 Most likely correct here.
>A card marked "Vector 8800V", which is a complete and utter disaster of Kynar
and flying components. I wouldn't let this thing near a running system. (seems
like a generic breadboard card, which has been built into some form of custom
hardware, has a large device marked "Analog Devices 940", and about 12 other
chips, plus a pile of discete components)

 I believe the 940 is an amplifier module but I'm not sure. It
could be a voltage converter as well. They made many discrete
circuit instrument amplifiers that had especially low offset
inputs. I would get this was an analog board of some type.


 It looks like a good project.
Received on Thu Jan 27 2005 - 13:09:20 GMT

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