General Category > Lisa Troubleshooting and Repair

Sun20 Formatting Issues

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AlexTheCat123:
I just got my hands on a Sun20 drive (firmware revision F) and it was working just fine, but I was curious about the drive's LLF-ing serial interface, so I tried formatting it in an attempt to document the LLF process.

Interestingly enough, according to the source code, the firmware will only jump to this diagnostic interface program if it detects an error when starting up, so I just unplugged the MFM data cable to make it give an error and then plugged it back in after getting into the diagnostic mode. After I got connected to to the drive over serial, I ran the F and F! commands to format the data tracks and the system track, respectively, but now I think I might've killed the drive by doing this. Whenever I power cycle the drive, I get an "Error reading system track" message over the serial port and it refuses to accept any commands from a Lisa. After looking through the source code a bit, it seems like this "system track" is the drive's spare table, so it's definitely important!

After looking through the source code some more, I noticed that many of the diagnostic routines seem to be unfinished (or just missing altogether) and that the more involved looking format routine that asks for the number of cylinders, heads, sectors, and a few other things (the F and F! commands don't ask for any of this stuff) never gets called at all because there's a JB instruction that just jumps over it if the drive encounters an error (which will always be the case when entering diag mode).

So I patched the ROM by replacing that JB with a few NOPs just to see if that formatting routine would work. Now it gave me a "No drives online..." error (which seems to be a lie because it can clearly talk to the drive in future steps) instead of the "Error reading system track" message, but sure enough, it let me enter all of the drive's parameters and then basically did the same things that the F and F! commands did (as well as verifying the data track format, which the F command doesn't seem to do).

All of those steps in the formatter seem to work just fine, but then it says "Error in writing system track" when it moves onto the step that actually tries to write a ProFile spare table into the system track. And I'm still stuck with the same "Error reading system track" message when I power cycle the drive with that JB instruction added back in. I'm not knowledgeable enough to try and troubleshoot/fix the formatting routines in the ROM, so does anyone have any insight into formatting these things? Am I just stuck with a dead drive or is there some way to recover from this? I'm going to feel so bad if I killed it as a result of my little experiment!

compu_85:
If someone else has a working SUN drive and access to an MFM Emulator, the disk could at least be read in so the control tracks could be understood.

Looking on Bitsavers, seems like there are at least 2 revisions of the Sun MFM board.

I see there's a rezero system track command, RZ!. Perhaps start there? Does the burn in test do anything?

-J

blusnowkitty:
A lot of the Sun20 disks I've seen on eBay listings have used the Kalok KL-230 drive, which according to history was one of the worst, most bottom of the barrel drives you could get back in the day. Is yours a Kalok? It may not have been your fault, the drives are just that unreliable.

sigma7:
If you haven't already reviewed this thread, have a look:

Sun20 Questions/Revival

In particular, note the "subtract 2" quirk.

AlexTheCat123:

--- Quote ---Looking on Bitsavers, seems like there are at least 2 revisions of the Sun MFM board.
--- End quote ---

I've got the older??? revision that has the three OMTI PLCC chips instead of just one.


--- Quote ---I see there's a rezero system track command, RZ!. Perhaps start there? Does the burn in test do anything?
--- End quote ---

The RZ! command works fine, but the formatter seems to automatically recal to the system track before formatting, so unfortunately that command doesn't really help with getting it to format.

And the burn-in test starts off okay, but it gets stuck on step 5 (reading the data tracks). Looking at the source code, it seems to just get stuck in an infinite loop on this step. And power-cycling the drive after getting through those first few steps of the burn-in test still yields the same error. Also, that burn-in test never asks for cylinders, heads, sectors, or anything else, so it just seems like it just runs the regular F and F! commands instead of that special formatter.


--- Quote ---A lot of the Sun20 disks I've seen on eBay listings have used the Kalok KL-230 drive, which according to history was one of the worst, most bottom of the barrel drives you could get back in the day. Is yours a Kalok?
--- End quote ---

Luckily, my drive is a Kyocera KC-20B, so I don't think the drive itself is at fault here. It seems like it's just the formatting that's screwed up.


--- Quote ---If you haven't already reviewed this thread, have a look:

Sun20 Questions/Revival

In particular, note the "subtract 2" quirk.
--- End quote ---

I already took a look at that thread and unfortunately, none of those suggestions seemed to help. And, despite what that thread says, it seems like you have to enter numbers in decimal instead of hex. It just gives the "oooh,oooh" error and makes you start over if you enter any digit that's not 0-9. I tried both capital and lowercase letters, but neither worked.

Does the Helmut Post guy from that thread who was working on the LLF procedure have a different revision of the ROM by chance? He seemed to be able to get things to work (and he could presumably get into the formatter without having to get rid of that JB instruction), so maybe the ROM revision matters? I've tried both D and F and they both fail the same way. I also tried revision C, but it doesn't do anything at all, so I'm guessing that it's only intended for use with the other revision of the control board.

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