I am occasionally getting an IO ERROR when executing commands, even when I successfully executed other commands before it gave me the error. If I check the kernel using CLOSED APPLE+CONTROL+RESET, it gives me the error message "IOU FLAG E5:1". If I check the kernel using the same method before the IO ERROR message appears in the console, the diagnostics tool tells me KERNEL OK.
To add to the confusion, after I run into the IOU FLAG error, if I reset the computer using OPEN APPLE+CONTROL+RESET, the drive cannot recognize the disk, spinning endlessly. In order to fix it, I have to take the disk out (after stopping the drive) and manually rotate the disk so that the index hole is visible. This manual fix also allows me to use commands after the IO ERROR message is shown (if I try without the fix it displays the error again. I have found this out from trial-and-error)
To make my and your brain hurt further though, the drive is very random. It can go for a long time without me needing to manual fix it, but all of a sudden it wants to be handheld by rotating the disk as stated in the paragraph above. I could not make a pattern out of this no matter how long I stared at the screen.
All of the above makes me think it is a drive issue (I have two Disk II's). If so, can anyone tell me what's wrong and tell me how to fix this or point me to resources that show me how to correctly fix this? I am a relatively new to vintage computing and have done maintenance on the Mac 128k internal floppy drive.
Is your IOU socketed? If so make sure it is seated properly. Not a bad idea to check all the socketed chips. Make sure you are grounded first of course. Check for any signs of corrosion, etc.
The business with the index hole is very odd, because the Disk II has no index sensor and there is no index signal to the interface card. So manually rotating the floppy disk is not doing anything.
The error "IOU FLAG E5:1" is a failure of the soft-switch test (see "Understanding the Apple IIe"). E5 is just the chip designation for the IOU chip, and 1 refers to the failed test. It means that the MIXED soft-switch was incorrect when its initial state was tested. MIXED is one of the latches that is not automatically reset, but is only initialized on power-up.
What could be happening is that after a crash (from what it is not apparent), the state of the MIXED soft-switch is different from what the diagnostics expect on power-up, so the test fails. This doesn't tell you anything about the cause of the problem.
These might or might not be relevant to your symptoms, but beware that a rotting diskette or rotting disk-jacket can cause symptoms like those:
Here are some photos showing various effects of rot on a batch of Photo Drive Up diskettes.
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IMG_1031.JPG
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Sorry for the mediocre quality of the photos, but I'm away from home right now so I don't have access to my camera -- these are just a handful of pictures that I happened to have loaded in a photo organizer on my laptop. (If anyone has good pictures of diskette rot or clogged heads, please share!)
The IOU is socketed correctly and there are no signs of corrosion anywhere on the boards, chips, or cards.
Good to note. Thanks.
I guess the manual rotation could've been dumb luck, or a result of corrosion as the comment below you states.