Remembering some odd PC problems in the past

[james_s]

While discussing some vintage PC troubleshooting I was reminded of two strange problems I experienced with different PCs many years ago, I never solved either one and the hardware is unfortunately long gone so I can't pull it out and have another go, I just got curious if anyone has speculations on what was really going on.

The strangest one, we had a Packard Bell 386sx-16 which came with a 40MB Western Digital IDE hard drive. The system worked perfectly in the stock configuration but some years later we tried upgrading the hard drive and ran into difficulty. Tried a 170MB Conner, a 250MB Maxtor and eventually a 340MB Western Digital, tried the onboard IDE interface and an ISA card that came with one of the drives, at one point got it to boot for a while on the 170MB drive but then it stopped. I remember I was able to get the 340MB drive working to the point where I could partition it, format it, copy files onto it, navigate the directory structure in DOS and list folder contents without any problems at all. The moment I tried to execute any program from the drive though the system would instantly hard lock. Primary while booting from a floppy or secondary booting from the original drive both behaved the same way. Ended up putting the original 40MB drive back in the system where it worked perfectly, built a new 386DX-40 system for the 340MB drive where that worked perfectly although that system had a weird problem of its own. Eventually scrapped the Packard Bell and continued to use that old 40MB drive for a few years for transferring large (by mid 90s standards) files around and it worked fine for that too. Darndest thing, it has bothered me ever since.

The other one was that 386DX-40 with a Sound Blaster Pro card which at the time was running DOS 6.2. Mostly it worked fine but in games that used wav sounds IIRC it would play the sound followed by an awful screeching noise vaguely resembling the squawk of a modem, it would make that noise about once a second while playing longer sounds. I remember trying everything, different IRQ, DMA and memory addresses, I lived with it for about a year before upgrading to a 486DLC-40 CPU on a newer board at which point the same sound card worked perfectly.

[chris_leyson]

I would put my money on buffer overrun.

[andy3055]

I would say that those were limitations on the MOBO.

[shakalnokturn]

I recall one, maybe two occasions when things actually worked as intended.

[james_s]

What buffer? This was a 386 running DOS, and the problem was clearly the motherboard, the same sound card, hard drive and software worked fine on a newer board but what was actually happening? It was either a hardware fault or a design flaw in both cases but what that was I don't know. I really wish I still had the hardware so I could stick a logic analyzer on the bus and see what it's doing.

[andy3055]

Could it have been the MOBO BIOS?

[james_s]

Beats me. I'm not knowledgeable enough about the very low level stuff to know what is different about trying to execute something off a disk and just creating/listing/moving/deleting files. I could run the DOS installation and it would go all the way through but then IIRC it would lock up as soon as "Starting MS-DOS.." was displayed. If I booted off another disk I could use the system but trying to execute anything stored on the hard drive would cause it to lock up instantly every time.

[Red Squirrel]

IRQ conflicts could be quite a headache, only ran into that once though.

Or random lockups.  Windows 98 was BAD for that.  You're just doing your work minding your own business then everything freezes for no reason.   Or random BSODs were fun too.   Windows 98 thought me to save my work often.

[james_s]

This was way before Windows 98 that I dealt with this, probably 1992-1993, I wasn't even using Windows at all with the 386, it came with DOS 4.0 and was later upgraded to 5.0 and I think eventually 6.

[GlennSprigg]

Then again... "MOBO" threw me Waaay off track, according to the 'Urban Dictionary' 
https://www.urbandictionary.com/define.php?term=Mobo
(I'm old, so I'll just shutup now!!)