Hi all -- I'm just going to repost some info that I posted on the MFM emulator discussion forum (the MFM HDD emulator project -- which is awesome -- is here:
https://www.pdp8online.com/mfm/mfm.shtml)
The problem with MFM drives, well, hey, yeah they all die. Soooo... I had been wondering about using a hardware MFM drive emulator on a microchannel machine. Got it working yesterday (yay!). I know there are alternatives (MCA scsi adapters, ZZXIO's great McIDE product, etc) but this one is also just fun, and I suspect MCA MFM Controller cards might be found on ebay not too expensive-ly? I haven't looked recently. That said, building the MFM emulator isn't really cheap (you can also buy a prebuilt one from these folks (no affiliation):
https://decromancer.ca/mfm-emulator) but hey -- inexpensive and MCA/PS2 don't really go together
-- MFM Discussion Post below --
Hi all -- not sure if this was already accomplished, but I was forever curious as to whether I could get the emulator to work with any of my microchannel PS/2 machines. I had acquired a model 80 with an mfm controller card and dead drive, and my model 50 came with a (working-ish) 20mb mfm drive and the model 50 mfm controller (both cards are equivalent, see
https://www.ardent-tool.com/storage/MFM.html), specifically the "late model" mfm adapter, IBM PN 90X8643.)
ANYWAY, long story short, I was able to eventually get it to work in my model 50 (I assume this will also work in the model 80). Using the 90X8643 card and the two cables that came in my model 80 (a 34 pin control cable with two drive connectors and a twist, much like an ibm floppy cable -- though I'm not sure if the twist is in the same location) and a 20 pin data cable, I connected to the emulator using the card edge connectors, set the drive select jumpers to 2 (e.g, DS1, e.g., second position in the jumper block of 1-4) and (CRUCIALLY) removed the resistor pack from RN1. There is a discussion on the ibm cabling on the page link above).
I set up a drive on the mfm with 615 cylinders and 4 heads (20mb) and set the PS2 bios to type 2 (a full listing of the IBM types is here (I think it's pretty accurate):
https://www.win.tue.nl/~aeb/linux/hdtypes/hdtypes-3.html
At this point the PS2 hated the drive. So I saved the changes to setup, rebooted back in, and pressed CTRL-A on the main menu to get to the low level format option. I chose that, and the PS2 complained that the drive wasn't ibm. So i pressed f3 and it asked if I wanted to "prepare it" and I said yes. It hated that too, so I pressed F3 AGAIN, and then it asked if I wanted to FACTORY prepare it, so I said yes, and away it went
This low-level format takes quite a long time, especially with bigger drives, so make sure you have other things to do.
After that, I was able to restart the machine (I had to actually power it down, not just reboot) and then installed dos 7 after using dos 7 fdisk to create a partition.
I was also alble to get a type 22 (30mb), type 4 (60mb) and a type 9 (112mb) drive working. Sometimes it was a bit gremliny and fdisk would fail with "can't read fixed disk". Playing with the arbitration level setting of the mfm controller card in the ps2 setup and powering off (rather than rebooting) seemed to do it, though I haven't yet 100% established the pattern. I think perhaps there's a bug in the ibm code somewhere, not sure.
ANYWAY, with stacker installed on the 112mb drive, I've got a nice model 50 with an mfm drive and a 250mb or so C partition. Happy! The emulator works a treat.
I also played around a bit with speedstor 6.5 when I was having the gremlins, but though it worked it didn't seem necessary, as the IBM setup low level format was always able to complete successfully. speedstor can be found on minuszerodegrees.net
Best to all, Alison
