Sardis Technologies ST-2900 RAM-512 Board

The ST-2900 RAM-512 board is an expansion board that plugs into the ST-2900 CPU board to provide 512KB of extra RAM, typically used for a RAM-Disk or a printer buffer.

RAM-512 board features:

(The new NVRAM/RTC board will have 4x the capacity, yet will be smaller and cost less to build, and will be non-volatile.)

Once I had built and installed a RAM-512 board in my main ST-2900 computer system, I was hooked! It was so much quieter, faster, fewer floppy disk swaps, less wear and tear on the floppy disks and drives, etc. It was bliss! Fortunately I lived in an area where power outages were rare, so I left the system powered up 24/7 and usually didn't lose any data for half a year or more. (Of course I backed up the RAM-Disk contents frequently, just in case.)

One of my industrial customers paid me to write custom software to allow using an ST-2900 CPU and RAM-512 board set as a large printer buffer.

The RAM-512 board is slightly larger than the CPU or FDC boards, to allow for two 60-pin connectors. At the time I designed the board I couldn't find an appropriate stack-thru connector (like the PC/104 bus used 2 years later), or at least not one that was affordable.

The RAM-512 board was announced on page 48 of the September 1985 issue of '68' Micro Journal, and reviewed on page 16 of the June 1986 issue.


(Click on a picture for a larger version.)

icon to link to photo of top of bare RAM-512 board icon to link to photo of bottom of bare RAM-512 board
Pictures of bare board. (943-981KB .jpg)
icon to link to photo of top of assembled RAM-512 board icon to link to photo of angled view of top of assembled RAM-512 board icon to link to photo of angled view of top of assembled RAM-512 board icon to link to photo of bottom of assembled RAM-512 board
Pictures of assembled board. (597-895KB .jpg)
icon to link to scan of PCB artwork for top side of RAM-512 board icon to link to scan of PCB artwork for bottom side of RAM-512 board
PCB artwork (first version). (176-225KB .png)

icon to link to RAM-512 User Manual ST-2900 RAM-512 Hardware and Software User's Manual.
(4.4MB .pdf scanned image)
icon to link to additional notes for RAM-512 board -- not available yet Other notes for the ST-2900 RAM-512 board. Includes addendum/errata to the manual, etc.
(not available yet)
(??KB .txt)
icon to link to .zip file with DSK images of FLEX and OS-9 drivers for RAM-512 board Two DSK images (35T/SS/SD FLEX format, 35T/SS/DD CoCo OS-9 format) of source code and binaries of FLEX and OS-9 drivers for ST-2900 RAM-512 board. Also includes bootable version of MEMTEST.
(25KB .zip)

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

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Last revised 2022-May-29 22:17 PDT.
Copyright 2018-2022 David C. Wiens.


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