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Hi,

I'm using CP/M 2.2b v2.3 on an 8800c with an FDC+ in Mode 4 (FD-55GFR as 330k 8") and I'm finding that my disks are randomly being marked as read-only, resulting in random fatal BDOS errors when I try to save my work in WordMaster, for example. A warm boot returns the drives to R/W but they flip back to R/O seemingly at random … the system sometimes cold boots into R/O, and other times consecutive runs of `stat` can show a drive flipping from R/W to R/O without anything else happening. My system is working perfectly in every other way (specifically I have had no other issues with the operation of my disk drives).

A possibly relevant data point is that I used single-density drives an Minidisk mode for many months and never saw this issue.

So my question is, how could this happen, and how might I fix or work around it? I would be perfectly happy just doing a hot patch with DDT to make the R/O check a no-op, if that's an option.

Anyway, I'm kind of stumped. Any suggestions would be greatly appreciated!

Thanks,

rob

Are you using HD media with the Teac drives?

Mike

Yes, it's new old stock 3M DS/HD 1.2M diskettes.

Sounds like the directory checksum vectors stored at the end of the BIOS may be getting clobbered. What RAM size does the CP/M banner specify when it starts? What are you using for RAM at the top of memory?

Mike D

I'm booting from your 56k CP/M image, using RAM (at 0000) and ROM (at F800) on the FDC+.

`survey` reports BIOS starting at C703, BDOS at B906, and ROM starting at F800 as expected. So there is some unused space above the BDOS I think.

- rob

It seems to be a slow corruption that gets worse and worse; if I reformat the disk and start over then it's okay for a while. I wonder if there's a hardware issue in both of my drives. :-\

Does CP/M report a read or write error and then set the drive to R/O, or does it just switch to R/O without reporting an error?

Mike

It switches to R/O without reporting any errors, and without any evident provocation. Consecutive runs of `stat` can show a drive flipping from R/W to R/O. I haven't experienced any other crashes or file corruption; this is the only symptom I have detected.

- rob

If it was actually getting corrupt data from the disk during directory access, you should be getting a bdos read error as well as the R/O change. It sounds like the directory read from disk has no error, but the corresponding checksums don’t match. This sounds like a possible RAM issue. Are you using the RAM in the FDC+ board? What other boards are in the system?

Mike

I'm using the RAM in the FDC+ but I can turn that off and install my Flex64 board, which I haven't tried out yet. Other boards in the system are an 882SIOJP and an 88-LPC clone I hacked up (definitely the most sketchy board in the system so I'll remove it just in case).