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AMPM: Alpha Micro AM-1200 Series

If the AM-1000 was Alpha Micro's Commodore 64, then the AM-1200 series was its Commodore 64C: essentially the same unit, but with improved engineering and a more refined design. Chief amongst its evolutions was better firmware and mercifully a proper SASI implementation, but it still retained the same form factor along with the similar overall feel and performance of its parent to function as a nearly exact replacement. You might consider opening the AM-1000 page in a separate tab and flipping back and forth for an informative comparison.

Despite its improvements over the AM-1000's idiosyncrasies, the AM-1200 is still the rarer unit (I do own two as it happens, though only one is operating), so it's not quite the landmark that the AM-1000 is. Like the AM-1000, the AM-1200 came in several derivative models, including the base 20MB hard drive-equipped AM-1200B, the 35MB AM-1200E and the 70MB AM-1200XP, the latter two having eight additional serial ports; we will illustrate both the vanilla 1200B and the 1200XP, which also has the 5.25" floppy drive option factory-installed (AM-210 FDC on an AM-220 I/O board, which is the AM-1000/AM-1200 version of the S-100 AM-210).

Pictures

Portrait, of the AM-1200XP, but the 1200B is the same. Admittedly, this is where the 64:64C analogy breaks down, since the form factor was intentionally the same and the two units from the outside looked pretty much identical.

The front panel, however, is different. The reset button is a more stylish black recessed job, and a disk activity light was added; unlike the AM-1000, the specific variant letter is not stamped on the badge. The floppy drive in the AM-1200 series is equivalent to the AM-1000's, using an AM-210 compatible FD controller which is on an AM-220 board.

Rear ports, first of the AM-1200B. The base 1200B has five serial ports, one of which is a DB-25 (for some reason) and the others being "DB-9" (DE-9), and a single parallel port. The VCR interface is on the right. The bottom right cover plate is for a Centronics-style external SASI interface, close enough for early SCSI drives and emulators that can be configured to act like one.

On the AM-1200XP (and AM-1200E), the port layout is the same but eight new ports are added on the lower right.

If we slide off the top, we get a look at the mainboard, which is fairly and unsurprisingly similar to the AM-1000 (take my word for it). The elongated DIP at the right next to the open position is the CPU; more about that in a second. This is of the AM-1200XP, but the AM-1200B is almost identical. Click the image for a 132K enlargement in a new window.

The top board is on a "hinge" and after removal of its restraining screws, simply lifts up. Notice the AM-1200XP's extra ports go directly to headers on the board, not to a separate card. There are jumpers next to the pin headers for configuring the individual port types. The serial hardware is already on the logic board, so adding ports to an AM-1200 is just a matter of adding the actual physical ports themselves.

In the AM-1200XP the hard disk is at left, which is an ST-506 drive connected to the internal SASI, but like many such systems is dead. I subsequently removed it and fitted it with a BlueSCSI attached to the external SASI port. The floppy drive is in the middle and the AM-220 board is on the right, with the power supply underneath it. The streamer (when present) and floppy drive connect to the AM-220.

The AM-1000 was only ever powered by the 68000, but the AM-1200 was announced with the virtual memory capable 68010 although AMOS/L never supported virtual memory. However, what it was released with is another story: initially the unit was, just like the AM-1000, released with a 68000 (as shown in serial #6106, the 1200XP, at right). Alpha Micro later did indeed ship the 68010 as announced, as shown in serial #52470 (the 1200B) at left, and at least some of these units ran at a faster 10MHz. I suspect these were in fact repurposed AM-1100Es reused as shippable AMOS systems after the UNIMOS line was canned. Nevertheless, notice that the official model number for both units is as part of the AM-1000 series!

Performance

There are effectively two performance tiers for the AM-1200, the original 68000 and then the later 68010. Both benchmarks are with with SI.LIT with an attached BlueSCSI to the external SASI port.

The 8MHz 68000 incarnation is nearly dead identical to the AM-100/L and AM-1000.

Computing Index (CX), relative to AM-100: 4.6
48 bit FP Index (4X), relative to AM-100: 4.6
Floating Point Index (FX), relative to AM-100/L: 1.0
Disk Index (DX), relative to ST-506: 3.0

The 10MHz 68010 incarnation is certainly faster ...

Computing Index (CX), relative to AM-100: 5.7
48 bit FP Index (4X), relative to AM-100: 5.7
Floating Point Index (FX), relative to AM-100/L: 1.2
Disk Index (DX), relative to ST-506: 3.4

... but all of these gains, except the disk due to I/O limits, are strictly scaled by clock speed (approximately 25%). That said, although the 68010's small microarchitectural improvements are effectively below the statistical noise floor, these later systems are still the ones to get. A 25% speed boost is nothing to sneeze at.

Potpourri

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