The GMX 6809 CPU III from GIMIX Inc. was a high-performance 6809 processor card for the SS-50 bus. It was designed specifically to run Microware's OS-9/6809 Level II operating system with minimal overhead, to maximize performance.

GMX 6809 CPU III features:

The GMX 6809 CPU III had similar capabilities as the CMS 9639 (for the EXORbus) from Creative Micro Systems.

Intelligent serial I/O boards for the SS-30 bus allowed many users to simultaneously use the system without bogging down the main processor with interrupts for each character.

A separate SS-30 bus CRC Generator board was available to speed up calculating the 24-bit CRC that each OS-9 memory module contains. Using the memory-to-memory DMA on the GMX 6809 CPU III, an 8KB module could be checked in 8.5 msec. vs. 455 msec. or more using the software routine. But it required masking interrupts for the duration of the DMA transfer to the CRC Generator because it wasn't reentrant. (Why didn't they rather set a "busy" flag to prevent starting another transfer until the first one was completed, to avoid masking interrupts?)

Does anyone have or know where to find a boot image for OS-9-GMX III? It would likely consist of the OS9Boot file on floppy disk or on a hard drive, as well as part of the kernel in an EPROM.

Søren Roug has posted scanned copies of several user manuals relating to the GMX III system, such as the DMA III disk controller and the OS-9 GMX III Support ROM. Unfortunately he hasn't found any boot disk image for the GMX III.

The history of GIMIX would also be very interesting. It appears that the founder, Richard Don, passed away in 2005, but I will try to contact his family to see if they would be able and willing to provide me some history.

(Click on a picture for a larger version.)
B&W ad photo (1.7MB .png) and color ad photo (525KB .jpg)
Pictures of Gene Buckle's GMX system (155KB-855KB .jpg)

Gene Buckle gave me permission to post pictures of his GMX system. The six pictures are:

The 2764 EPROM on the SIOP3 board says "OS-9 V2.00 (c) 1983 MSC". I wonder if that means it is actually running a separate copy of OS-9 Level I on this I/O board? The purple chip at the bottom is an AMD Z8038 Z-FIO, which is a dual-port 128-byte FIFO buffer that provides an interface between the 6809 on the SIOP3 and the 6809 on the GMX 6809 CPU III.

GMX 6809 CPU III User's Manual.
(scanned image, 5.8MB .pdf)
GIMIX CRC Generator Board User's Manual.
(searchable scanned image, 207KB .pdf)
Microware OS-9 Level Two System Designer's Guide (handwritten annotations are mine).
(scanned image, 5.2MB .pdf)

"OS-9" is a registered trademark of Microware LP.

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Last revised 2021-Nov-27 11:56 PST.
Copyright 2021 by David C. Wiens.

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