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Service technician diagnostics disk for QNX 2 machine?

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Service technician diagnostics disk for QNX 2 machine?

Postby obsol33t » Tue Dec 05, 2017 10:50 pm

I have an old CEMCORP/UNISYS Lexicon server from the mid-late 1980s that was used to run a network of ICON terminals in a school. It boots the "ICON Series System Software 3.00.04" which is based on QNX 2.05b. It seems to be working well.

I've imaged all of the floppy disks that came with it as well as the MFM hard drive. I have installation disks for the ICON Series SSW versions 3 and 4. I want to use version 4 so that I can install some newer applications, and bought a second MFM drive to install it on. It is a Seagate ST-4096 80 MB drive.

A former student assistant network administrator of these Lexicon servers remembers a teacher calling in a service technician to work on it one day. He had a special service technician diagnostics disk that could do things like low level format a drive, and maybe even change the drive geometry settings. This former student recently imaged the ROM chips and disassembled the code. He discovered that it is hard coded to use 17 sectors/track and 4 heads, so only the number of cylinders can be increased to a maximum of 1023 which means it can only use up to 33 MB. The WD1002-05 controller doesn't seem to have a BIOS that I can enter on boot to configure anything.

I'm hoping that someone here might be familiar with mid-late 1980's computers running QNX 2, and might know what this mysterious service technician disk may have been. It would be even better if someone has an image of such a disk! I've tried booting an MSDOS boot disk on the machine and it won't boot. I suspect it might only support booting a QNX 2 filesystem.

Any help would be greatly appreciated.
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Re: Service technician diagnostics disk for QNX 2 machine?

Postby maschoen » Fri Dec 22, 2017 4:04 am

I'm somewhat familiar with drives of that period. Here's what I recall.

QNX 2 has a low level format program for floppies. I don't think it worked on hard drives. I believe you are right that it would take a special program. These are very old drives you are talking about. Once we started seeing IDE and EIDE drives, low level formatting was not something that was done. The drive handled such issues internally. I could be wrong, but the idea that a 80Mb drive is still functional seems unlikely, especially a Seagate. I have a lot of old drives that I used on QNX 2, none that old that are working.

I imagine the disk you mention was put together by the ICON people. I don't think QNX had such a disk. The type of "geometry setting" that you could change on such a drive was the interleave between sectors. The idea is this. If a drive had zero interleave and you asked the controller to read one sector and then read the physically next sector, you could guarantee a complete rotational delay. If you asked the controller to read multiple sectors, one right after another, it would. Until later in its life, QNX 2 always read just one sector at a time. I'm pretty sure I wrote the first driver that would read multiple sectors and cache them. This was for an Iomega Bernoulli Box would had a relatively long rotational delay. If you formatted the drive with the right interleave, you could increase performance. Later drives did automatic internal caching.

If you have a DOS program that will low level format the drive, you should just get an old PC that you can run DOS on and format the disk.

I've been pretty successful in running QNX 2 on EIDE drives. I think up to 500Meg is no problem. After that you might not be able to use the extra space. I wrote an IDE LBA driver for QNX 2 that is available if you think it will help.
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