I often buy machines that need repairs because they are much cheaper and i get a kick out of fixing them.
I have benefited from a lot of support from ARC members. I try to pay those debts back/forward by doing repairs for other people. There are many in the vintage/retro community who do this. Andrew P and Daniel immediately come to mind.
This sometimes gives me the bonus of working on machines that i don’t own and has included a Lisa, A2000, X68000, 128D, Computer phone, ECS 4500, Microbee etc.
If i agree to do the job there is no labour cost, no warranty and no time limit! There’s no harm in asking, particularly if you have something interesting. No recaps though; i loathe them.
This machine is as much a tool as it is a toy. I use it to run the Proteus EPROM programmer (thank you, Andrew) which is very handy for programming old school EPROMs with high programming voltages.
The machine is quick enough to operate well with Windows 3.1 as well as doing a good job with a lot of DOS games.
Pro-Log was a major manufacturer of STD cards. The cards here arrived in a collection of almost 100 STD cards (thanks yet again, Andrew). I guessed by their appearance and dates that they probably went together, and later found that they were all related to a Pro-Log System 20.
The card cage is not the original unit but works fine. The system boots a ROM version of MS-DOS 3.2. The ROM card also has 128k of RAM for a RAM disk with provision for battery backup.
The 8088 processor card has 128k and with two additional 256k RAM cards the total system memory is 640k.
The system also includes a CGA card, floppy disk controller card, printer card, and a prototyping card.
The system includes a solid state disk drive card with two drives (nominally H: and I:) each of which can hold 4x 64kB EPROM or static RAM.
The H: drive has three EPROMs programmed with MS-DOS 3.2. Imaging the ROMs and concatenating the binaries produces an image file just like those used with a Gotek or a Greaseweazle.
An operator’s manual was and utilities disk were recently uncovered from the same source as the cards. It would have been better at the start, but it confirms a lot of things and hints that there was once a SCSI card available. It also lists compatible 7000 series Pro-Log I/O cards.
The system has two SASI cards that I thought might accept a SCSI2SD card.
The drive configuration comes up in two places – firstly in configuration of the master or single user system configuration program, and then again when the drive is formatted.
In both cases, the following information is required:
SASI card number: 0 worked for one card but I tried multiple numbers with the other card without success
Drive Number: It allows 1 or 2. 1 seemed to be SCSI ID 0.
The configuration also deals with partitioning. The default partition size is 4MB which is the optimal size. With large drives, that’s a bit of a nuisance because you need a lot of partitions. Having some optimal 4MB partitions and a larger sub-optimal partition seemed like a reasonable compromise.
The drive selection gave some geometry, but the specifics probably don’t matter with a SCSI2SD. The SCSI2SD was set up with a simple 32MB disk at ID 0 with 512B sectors. Termination needs to be on.
The process went like this:
Create a fresh single user floppy disk
Run the Configuration program and select modify
Set up the hard disk as above
Format the hard disk using HFORM30 with the same disk parameters
At this point the new drives were available starting at E: but when the directory was listed it appeared the disk was read only and the directory looked corrupted. It didn’t seem to matter if the format was done first and then the configuration.
The “Creating Boot Tracks” section of the System Initialisation Procedure mentioned a program called ERASEDIR but really just in the context of making faster hashed entries. Running this program on each of the drives resolved the issue. It says to run this after BOOTDISC (which writes the boot tracks).
So:
Run BOOTDISK and write to E: – only the first partition can be a boot partition. It can also be written to A:.
Run ERASEDIR on each of the new drives from e: to the last one.
Copy all the files from the A: to E: using DO DCOPY A: E:
When the system is powered up, it looks for a bootable drive. If a boot floppy is in A: it will use it; otherwise it will boot using E:.
Importantly, a floppy disk drive must be connected otherwise the system will not boot from the SASI
Programs were then copied on to the solid state disk from a gotek. TurboDOS supports multiple user areas so the these can be used as directories. User 0 files marked a global can be accessed by all users.
All users are assumed to be using Televideo 950 terminals. A lot of the software on the 8″ disks was configured to use this popular terminal.
This was a home build based on the Pulsar Little Big Board. The machine came with an open rack with two 8″ floppy disk drives and some scary looking power supply wiring. It runs CP/M or TurboDOS.
The mains wiring and chassis earthing has been brought to a level where it no longer strikes fear. The chassis has been enclosed in clear perspex so that the authentic bespoke build and striking 8″ floppy disk drives can be enjoyed.
The drives are Y-E Data YD-180.
The Little Big Board design is well known in Australia, having been published in Electronics Today International.
