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WD Silicondrive 512MB CF issues on 486

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First post, by keenmaster486

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System: 486 DX2/66 with a VLB IDE controller and Startech 3.5" drive bay CF adapter.

System worked perfectly with an ordinary IDE hard drive previously.

Trying to use a WD Silicondrive 512MB CF card now.

I have four of these cards and have tried two of them so far with the same results.

The BIOS autodetects the geometry as 1011, 16, 64.

I can easily FDISK and FORMAT the cards with a single primary DOS partition, and copy the system files as I normally would, and it boots just fine.

I can copy files to the drives.

Here's the problem: it only *mostly* works. I get random read errors, and it seems to alternate between being very fast and very slow (if I open EDIT and close it over and over, sometimes it loads instantly, and others the HDD light flashes for a second before it loads).

I can consistently make it fail if I try to load Commander Keen 4, 5, or 6 (not 1, 2, or 3). It doesn't make it past the loading screen - and crashes with a "terminal error drive C" or something like that.

I've tried loading files onto the card from a modern PC with USB adapter and FTPing files using MTCP (keeping the CF card only in the 486 from FDISK onward) and there's no difference in the behavior.

Any ideas?

World's foremost 486 enjoyer.

Reply 1 of 4, by mbbrutman

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It sounds like a timing issue or an older CF card. Try to slow down the machine in the BIOS or slow down the onboard IDE controllers directly. If you can get it stable at a lower speed that would be a good data point to have.

Even though they are supposed to be drop-in replacements, CF Cards are not IDE hard drives. There may be small timing or error handling differences.

Reply 2 of 4, by keenmaster486

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mbbrutman wrote on 2025-03-17, 17:24:

It sounds like a timing issue or an older CF card. Try to slow down the machine in the BIOS or slow down the onboard IDE controllers directly. If you can get it stable at a lower speed that would be a good data point to have.

Even though they are supposed to be drop-in replacements, CF Cards are not IDE hard drives. There may be small timing or error handling differences.

Makes sense. But if I get it working at a slower speed, how does that help me other than to tell me that the CF card isn't broken? I kind of already knew that since both of the cards I've tried have exhibited the same behavior.

I forgot to mention I did purchase a 512 MB SanDisk Ultra II card NIB on eBay to serve as a "control" / primary card if I can't get these working, so I'll have to report back when I get that one if it works.

World's foremost 486 enjoyer.

Reply 4 of 4, by douglar

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I think those WD Silicon Drives have a small "on-device" ram cache. Could that explain the performance variation?

Check the device firmware version using an ATA info tool if you can. It might clue you in on the date of the device. WD Silicon Drives have been around for a while. Some of those small capacity WD Silicon Drives are old, like really old. If the firmware is older than 2003, I would avoid the drive unless you are looking for a challenge. I found that some of those early CF's use noticeably slow flash and flash controllers. Slow enough to notice on a 486. Slow enough to make you consider using a hard drive instead.

What VLB card are you using? Older controllers often had jumpers that let you manually configure the transfer rate. It's possible that your VLB controller is jumpered incorrectly.

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