My ST-2900 Computer Systems

I sold my last remaining inventory of ST-2900 boards and components in 2017, but kept three complete systems, which are described on this page.

(Click on a picture for a larger version.)

System 1

System 1 pictures (530-957KB .jpg).

System 1 is a fully configured 3-board (CPU + FDC + RAM-512) ST-2900 system that was my main computer for many years. It is powered by an Apple II clone switching power supply, and is mounted onto a 1/8" aluminum base plate, but has never had any cover.

It has two 5" 360KB floppy disk drives -- full-height Qume QT-542 and half-height QT-142. I connected a used Cybernex MDL-110 CRT terminal (made in Canada) running at 9600 bps to serial port 1. Serial port 2 went to an SPE-1 switch, one port of which connected to my SwTPc 6809 system running FLEX/9, and the other to a modem. A Star Micronics Gemini-10X dot matrix printer (connected to the SwTPc's parallel port) rounded out the system. My SwTPc by this time was used only as a printer buffer and EPROM programmer -- poor thing!

The Qume QT-542 floppy disk drive was wonderful. After I configured it for the optimal step rate, it was fast and quiet and reliable, making only a soft swishing sound when seeking, not buzzing like some drives. But it cost me almost C$450.

When I added a RAM-512 board to this system, it was even better! The RAM-Disk made no noise whatsoever, was much faster than a floppy disk drive, and having a third "drive" minimized swapping floppy disks. It wasn't quite as good as a hard drive, but was the next best thing.

I haven't powered this system up for over 21 years, so don't know if it still works. If and when I get it cleaned up and working again, I might be interested in selling it.

System 2

System 2 pictures (44-73KB .jpg).

System 2 is a 2-board (CPU + FDC) system that was originally assembled by my brother and used by him for about two years. He also built the custom sheet metal box (approx. 9" x 10" x 5"). It has an Apple II clone switching power supply.

The 3" floppy disk drive is a single-sided 360KB Shugart SA300 that cost almost C$300. Its size matches the ST-2900 boards very well, and the system garnered lots of interest whenever I exhibited it. On the rear panel we installed a connector to allow attaching one or two optional external 5" floppy drives. We never did install a second 3" drive even though the box has room for two drives.

Instead of using an expensive separate CRT terminal, we installed a Term-Mite ST video terminal board from MicroMint, connecting it to a keyboard from a surplus Microtel Telidon system, and a 12" NEC JB-1201M monochrome composite video monitor.

My brother also successfully repaired a surplus GE TermiNet 1200 printer to use with this system. Someone had sheared off all the card-edge fingers on its many circuit boards so they could sell the gold! The printing mechanism had raised characters moulded on the ends of metal fingers that were attached to a rapidly rotating flexible belt. Little solenoid-operated hammers hit the fingers at the right time as they passed by, achieving approximately one complete line per second (120 characters/sec.), which was quite fast for its time.

Eventually I designed and built the SASI adapter to connect an external 10MB hard drive to this system. It was then used mainly to run my custom accounting software for several years.

When the Term-Mite failed, I connected a used Qume QVT-102A CRT terminal to this system instead.

I haven't powered this system up for over 21 years, so don't know if the computer or hard drive still work. If and when I get them cleaned up and working again, I might be interested in selling them.

System 3

System 3 pictures (354-480KB .jpg).

System 3 is a 2-board (CPU + FDC) system in a custom aluminum chassis (approx. 5" x 9" x 6"). The cover was cut from my SwTPc system's cover (sorry!). It has a Power-One linear power supply.

I exhibited this ST-2900 system with two borrowed external 5" floppy disk drives at the Vintage Computer Festival in Seattle in February 2018. I used a Toshiba T2400CS (1994-era '486 notebook computer) with Windows 95 running HyperTerminal as the serial terminal. I demonstrated FLEX and OS-9 running on this ST-2900.

But I originally (in 1990 or 1991) intended to run this as a diskless system, connecting its serial port(s) to an IBM PC clone, which would run software to allow the ST-2900 to use the PC's keyboard, display, printer, floppy and hard disk drives, etc., similar to the DriveWire software for the CoCo that came out several years later. But I never finished my software.

I wrote a driver for OS-9 to implement a tiny RAM-Disk in the ST-2900's main memory (since this system doesn't have a RAM-512 board). OS-9 was to be booted by converting the OS9Kernel and OS9Boot and RAM-Disk files into Motorola S-Record (S19) file format, then loading them into the ST-2900's RAM via the serial port using ST-MON's 'L' command and the upload command in a terminal emulation program on the host PC. I don't remember whether I got it working at that time.

I am currently upgrading this software, which will eventually allow booting and running OS-9, NitrOS-9, FLEX, or SK*DOS, on an ST-2900 system with no disk drives connected. Of course loading the operating system via a slow (9600 bps) serial port, and only having a tiny RAM-Disk that can't be saved, is of limited use. But it's a fun project.

When the NVRAM/RTC board becomes available, I will install one in this system to allow it to boot and run without any floppy disks, but without needing to upload the operating system via a slow serial port. And it will provide lots of non-volatile storage for programs and other files, finally making this a very useful system. But how will I load files onto the NVRAM/RTC board?

One other ST-2900 user has ported DriveWire to the ST-2900, including the ability to boot (Nitr)OS-9 via DriveWire. This will make a diskless system even more capable and easy to use. And it will make it easy to get files to (and from) the NVRAM/RTC board.

"FLEX" was a trademark of Technical System Consultants (TSC).
"OS-9" is a registered trademark of Microware LP.

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Last revised 2020-Jun-23 13:43 PDT.
Copyright 2020 by David C. Wiens.

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