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Shutdown screen oddities on LC III and 475

LazarusNine

Well-known member
I've been going through trying to determine the state of a few of my machines recently (all have recapped logic boards), and I've noticed a sporadic oddity when shutting down, and I don't know if it's related to a logic board issue, something to do with the aged HDD or even the PSU. If you look at the attached photo, you'll see that the 'safe to shutdown' screen is missing a bunch of letters. It doesn't happen every time I shut down, but it is relatively frequent. Any idea what could be causing this? Faulting ROM chips? RAM? VRAM? It's just a bit of a mystery to me. It's happened on both an LC III and my one (sort of) working 475. Mind you, I was swapping the HDD between them, and I will be testing a new PSU later today (mAcTX for LC with Pico PSU) and swapping in a SCSI2SD drive solution tomorrow.
 

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Byrd

Well-known member
Presuming every other function while the computer works is fine? No glitching in OS, games, etc? I'd be reinstalling the OS fresh, or boot without extensions to see if you can replicate it.
 

Crutch

Well-known member
That is extremely weird. I doubt it’s anything in hardware. What System version are you running? The fact that all the f’s in the message are missing almost makes me think your Chicago font in RAM got corrupted somehow. But I don’t see how that could happen in such a targeted way that wouldn’t break other things or be noticeable elsewhere. Mysterious.

Yes try running without extensions and a fresh System install. I bet that fixes it. I’d love to know the cause though.
 

joshc

Well-known member
I've had similar weirdness before when the System file was corrupted, try a fresh reinstall.
 

cheesestraws

Well-known member
Mind you, I was swapping the HDD between them

If it moved with the HD, then it's probably either the HD or the software on it. My bet would be on the latter, though that doesn't explain why it would only happen sometimes. That said, a hard drive failure that only affected the letters 'uppercase I' and 'lowercase f' sounds almost too bizarre to be true (though nothing is too bizarre to be true of computer hardware). So, try a reinstall first I suspect?
 

bdurbrow

Well-known member
HDDs are lossy storage devices; even back then they used error correction codes to function. It could well be a sector that's marginal; and for whatever reason the error correction is intermittently returning something non-printing in the affected locations of the "It is now safe to" string.

The reason why SpinRite works is that it's exercising the drive, over and over, coming in at various directions and speeds (well, seek distances), essentially "rubbing the controller's nose in it", until it gets one last good read before marking the sector bad and writing the data someplace else.
 

dan.dem

Well-known member
Do you have RAM Doubler installed? The off center "Restart" in the button indicates it, if memory serves me right. Probably, this is what messes up your fonts.
I cannot believe that an altered HD content can happen without the internal error correction throwing a read error message. So I think it is a software error, likely a corrupted system or font file or system extension.
 

bdurbrow

Well-known member
Early error correction wasn't nearly as robust as modern devices have. A fair bit of early weirdness was traced back to just that. Usually, when a marginal sector is detected, it just gets silently moved; but if it has developed multiple bit errors in both the main data and the ECC bits - especially if the center of the track is OK, but the edges are where the problem spots are - it could happen that the entire sector computes OK, when read with both the corrupted data and the corrupted ECC values.

Or, there's something happening at runtime that's overwriting those specific bytes; perhaps a race condition (thus it being intermittent). I'm afraid I don't remember enough MacsBug to know if you can watch the page of memory to catch whatever it is in the act.
 

LazarusNine

Well-known member
Thanks for all of these replies. It truly is a bit perplexing. @dan.dem I don’t have RAM Doubler installed on this machine, but that was an interesting observation. @Byrd Weirdly enough, this is the only evidence of any kind of issue or corruption I’ve noticed in the usage of the computer. Everything else seems so work as expected, aside from the fact that the five year-old battery I have in there needs replacing, as certain system settings are not retained after a full shutdown. @joshc Yep, I’m just going to a do a full reinstall on a new HD (BlueSCSI) once that arrives. Will keep you all posted if the problem resurfaces after that.
 
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