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AMPM: Alpha Micro S-100 Models

Alpha Micro, of course, started in the S-100 business with their WD-16 offerings beginning with the 1977 AM-100 two board system. This was quite lucrative for the company and even after introducing non-S-100 units such as the AM-1000 continued to produce S-100 systems well into the mid-1980s.

Since most of the S-100 systems are largely minor variations on a theme, I have chosen to subsume them all into this grab-bag page. Most AM S-100 boards are fairly vanilla technically except for the AM-100 itself, which uses some of the S-100 lines for DMA and many not be generally compatible with later systems. For that matter, while most of the other cards are properly bus-compatible, they may not be case-compatible: some of these cards are quite large and may not fit in anything other than a real Alpha Micro card cage.


This is an AM-1041, a fairly typical S-100 system, although it appears to have been upgraded to what is effectively an AM-1042 (I'll discuss the difference in a moment). It comes as two large, heavy! rackmount boxes; I purchased it from a collector (hi, Bob!) which was in fact the first such unit I have seen on eBay in close to a decade.

The top one is the S-100 card cage, shown here open. We'll come back to it in a moment.

The bottom is the disk box. Both the top and bottom boxes have the reset button, status window and power keyswitch, which I don't have keys for; the reset button is not connected in the disk box. The left slot goes to a really rusted out tape drive, and the 32MB Winchester hard disk is in the middle.

Rear ports. The S-100 card box has a staggering full 16 ports, the maximum for this form factor, and all of them are active. The disk box is exactly the same except the (obviously) non-functional ports are blocked off.

Inside the disk box. This drive was a fairly lately manufactured Winchester-type drive, with an installation date of 1987. The tape streamer and hard disk are under the same cage.

Back to the card box now. There are six cards installed in the AM-919 motherboard in this unit, two visible here; from front to back, they are an AM-710 memory board, an AM-100/L 68000 CPU board, an AM-500 hard disk controller and three AM-300 serial boards. The AM-300 serves a whopping six serial channels, so three gives us eighteen potential ports, of which the backplane has only room for the 16 we saw! As for the AM-500, it's a fairly straight-forward DMA-based HAWK HDC with a Zilog Z80 CPU.

The AM-100/L. Strictly speaking, the AM-1041 is a AM-100/T unit, which is WD-16; the AM-1042 is exactly the same as the -1041, but has the /L (and is 68K-based). It is a testament to Alpha Micro's thoughtful design that, once you updated the software, the hardware upgrade meant simply replacing the CPU board because the bus lines were already swapped to maintain the same endianness. Indeed, this appears to be exactly what happened with this unit. The 68000 CPU is the largest chip, at the bottom middle near the card edge.

Finally, guess which backplate goes to which unit. ... Okay, wrong. The AM-1041 logo is actually on the disk box; the AM-900-02 label goes on the card box.

This unit is not currently operational. Although it is physically intact, the fuses and fuse holders are gone and I have no keys for the power switch, so I'll need to install new holders and fuses and bypass the key to get it to a state where I can even test it out. This is too big to do right now. When I get a little more room on my workbench, we'll be trying to get this beast to run, though I am somewhat apprehensive about the state of the hard disk (and the streamer will need a lot of reconditioning).


One of these days ...
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