The Peripheral Technology PT-69, which was only 50% larger than the ST-2900 CPU board, was probably the main competition for the ST-2900.
The PT-69 started shipping almost a year before the ST-2900. It appears that one of their main design criteria was to make it totally compatible with software for SwTPc SS-50 bus systems, whereas I was willing to forsake some compatibility for superior features. (In any case, the effort to make software compatible with the ST-2900 was usually fairly minimal.)
A comparison of the ST-2900 vs. the original PT-69:
At first only TSC's FLEX operating system was available for the PT-69, but later they also offered OS-9 Level I and STAR-DOS.
There are some details I don't know. How did the PT-69 generate its baud rate clocks? My guess is that they might have used a 14.7456 MHz crystal for the SAM chip, thereby running the CPU at only 921.6 kHz, and picked off the selected 16x baud rate clocks from a /3 and /2 divider chain fed by the 3.6864 MHz output of the SAM chip. Did they implement a periodic interrupt to support FLEX printer spooling and OS-9 multi-tasking? If so, did they use the MC146818 to generate it? At what frequency? Did the clock chip have battery backup circuitry and a connector for an external battery, or an on-board battery holder?
The only information I have found so far on the PT-69 is from ads and reviews in '68' Micro Journal. If you have more information on the original PT-69 board, such as color photos, user manuals, schematics, or EPROM dumps or listings, please contact me.
The editors of '68' Micro Journal reviewed the PT-69 on pages 19-21 of the November 1984 issue. Several users wrote in with fixes for the PT-69's problem with incompatible disk formats, such as pages 38-40 in the June 1985 issue, and pages 49-51 in the September 1985 issue.
(Click on a picture for a larger version.)
Ad in October 1983 '68' Micro Journal.
"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-Jun-01 12:30 PDT.
Copyright 2019-2022 David C. Wiens.