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Using GoTek floppy emulators on a Professional 350/380

czunit

Veteran Member
Joined
Aug 7, 2015
Messages
764
Good morning!

Wanted to get this down here for others who might have this issue: I have a pair of Professional/380 systems that I used to use long ago with P/OS 2.0. One system had a RD52 drive (31mb) and the other had an RD51 (10mb). The better system has a working RX50+controller, hard disk controller, 256k external memory, a TMS board (with daughter card and phone base) and a genuine Ethernet card, condition unknown.

So I finally decided it was time to load up POS 3.2 on a slightly larger drive. I had a working RD53, which is pretty much the biggest disk you can use on a Pro so I started with that. I had done a fair bit of work restoring both disks of a pair of RX50's, so I had those. And I had an old Compaq DeskPro/4100 running Windows 95 that I could use to make disks and the DECUS downloads for POS and some of the other applications. I also have a pair of GoTek's, but they didn't seem to work on the 380.

First step was to get disks made. The compressed images on the DECUS archives can be expanded easily with 7Zip but then they are in a TeleDisk format and that program is old, and doesn't really work on DOS emulators with USB equipped floppy drives. Drat. So I fired up the 4100 (getting that going was an adventure), started making disks, then the 1.2mb drive failed due to dirt and debris from old disks piling up on the head. Made enough floppies to load the basic OS, but this was not going to work for all the accessories like Synergy and Pro/Toolkit.

So I started looking at the GoTeks. It turns out there is a DOS program called SAMDisk.exe (made by world of SAM) which DOES run on Windows 10 DOS and CAN convert teledisk to .DSK extensions which a Gotek with Flashfloppy can read. Hooked a Gotek to my 11/73 to verify I could mount a disk under RSX (yes, they are good) then tried two of them with a 34 pin ribbon cable to the Pro floppy interface.

No dice. Tried various jumper combinations, sometimes it would pass diagnostics, but would never mount the disks. Then in one iteration I found that if I switched the disk while it was trying to read the volume mounted briefly and crashed the system. Interesting.

Reading the RX50 documentation I saw that the key to the RX50 is it's a true Shugart interface, not "ibmpc". This means the disk ready signal and the door closed signal are reversed and that is what threw the Professional. It doesn't affect RQDX3 equipped sytems, probably because we just do a mount command to mount floppies and they don't watch the state of the door and disk ready.

So here is the proper configuration:
On the first drive, set the drive select jumper to position 2
On the second drive set the drive select jumper to position 3
Use a true 34 pin straight through ribbon cable, don't use one with a twist. If you only have a twist one, remove the cap at that end and reverse those ribbons to make it straight through.
On the FF.CFG file make sure the drive type is set to Shugart (not IBMPC) and the default is set to RX50.
Remove any other jumper you may see on the gotek crossing the last two pins.

Then hook it up and give it a go. I was able to boot the the diagnostic disks (requires both drives) as well as POS install media. You can change disk images during install, I recommend selecting the next image when the computer is waiting for it, then waiting a few seconds for the GoTek to settle down and the OS to see the disk and mount it.

So far the system is now up with the DECNET software installed (and passing loopback tests), Synergy running (more on that later, problems), and even the Pro/Serve software so I can make the system into a Decnet server. There's a lot in there, and it's much easier to install with the GoTeks as opposed to a large pile of floppies.

Good system. Let me know if this works for you.
 
No problem. I loved the Pro, and one of my pet projects now that I have it running is to figure out how to do a Sysgen of M+ to support the Split I/D of the Pro/380. I don't think it's impossible, just need to do a lot of trial and error. Which would be a lot easier with virtual floppies and a Gesswin disk emulator to do snapshots. :)
 
Which GoTek model works with DEC Pro? There are many models on the web page.
 
They have to be flashed with the proper code. Best bet is to buy one on Ebay that is already flashed for Dec use. I believe that is flashfloppy
 
From my own experience, the hardware doesn’t matter. But make sure to run the flashfloppy software on it. There are version with nice oled display and encoder nob. They are handy if many different floppydisk images are on the USB stick.
 
I discovered that my Pro350 will always fail the floppy drive POST test unless the first Gotek has a diskette image selected. If you intend to boot from the hard disk, just use a blank formatted image. After a week of studying logic analyzer traces and a lot of fiddling around I was never able to figure out what it was looking for. The RX50 drive does not behave this way, I finally built up an 8051Dumper and grabbed a firmware image from the diskette controller board. One of these days I'll get inspired enough to disassemble it and get the answer. If anyone else wants to take a crack at it drop me a PM and I'll send a copy.
 
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