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IBM CGA Card Artifacting during Read/Writes to the Hard Disk

ButINeededThatName

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Nov 29, 2018
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Fort Wayne, IN
I've been running SpinRite for the past half-hour and it has made me aware of a very strange issue with my CGA-equipped 5160 (early style IBM CGA adapter), that being that the display gets a nice (un)healthy dose of artifacts that I can only describe as "multi-colored hyphens" whenever the hard disk controller (original Xebec controller) is writing data to the disk (ST-412). It's honestly one of the more humorous issues I've encountered, though it does get a little annoying after awhile. Thankfully, it only seems to happen in GUI environments.

Has anyone encountered anything similar or have a possible solution? It's not a massive deal if I can't get it sorted out since I probably won't be writing appreciable amounts of data in GUI environment, but I'd still like to sort it out if I can.
 

Ruud

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Heerlen, NL
No. Is it possible to try another CGA card? If not the same type, another one then?
 

reenigne

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Dec 13, 2008
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Cornwall, UK
Have you only noticed this in SpinRite and not while booting DOS? It's probably just operating in 80-column text mode and writing directly to VRAM without taking anti-snow precautions. This is a known issue with the original IBM CGA cards, not anything to do with the drive.
 

ButINeededThatName

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Nov 29, 2018
Messages
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Fort Wayne, IN
No. Is it possible to try another CGA card? If not the same type, another one then?
Unfortunately this is the only CGA card I have on-hand.


Have you only noticed this in SpinRite and not while booting DOS? It's probably just operating in 80-column text mode and writing directly to VRAM without taking anti-snow precautions. This is a known issue with the original IBM CGA cards, not anything to do with the drive.
So far it has only happened in SpinRite, but I also haven't ran many other programs with "graphics" outside of the DOS Shell. I do have it set to run in 80-Column mode, so that could be it. It's strange that it only happens during the program cycling between read and write commands, though.
 

vwestlife

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May 2, 2008
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central NJ
I'm pretty sure it's just typical CGA "snow". Try running a command-line program that accesses the hard disk, like CHKDSK. You should not see any snow then.
 

Eudimorphodon

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May 9, 2011
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Upper Triassic
Just for a laugh I wrote this. I don't have an original IBM CGA card so I can't say exactly what it'll look like, but I'm pretty confident it'll make it snow for you if you want to try it and see if that's a likely explanation. (Don't worry, it's harmless, all it does is poke one memory location in CGA video memory in a very tight loop. Hit escape to exit. If some benchmarking I did of another program I wrote that does something vaguely similar is correct it'll probably pretty much tank your entire screen while it's running with exactly what you're seeing in Spinrite, if the snow theory is correct.

On the flip side, if your video card doesn't snow this program does nothing, you'll just see a rapidly flickering/changing character in the upper left corner.)

I second that it's almost certainly just regular old CGA snow. It's been a long time but my recollection is that SpinRite displayed this constantly updated "map" of your hard disk on the screen while it did its business, and if it didn't specifically make an attempt to avoid snow I'm guessing it was just perfect at triggering it.
 

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