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Memory parity error when doing large disk operations?

OK, so the first three bytes of C000.BIN are 55 AA 40. 55 AA is the signature bytes for an option ROM, 0x40 * 512 is telling the BIOS to expect 0x8000 bytes, putting the end of the ROM at 0xC7FFF. (And, in fact, the ROM is empty past 0xC78B3.)

Mysteriously, C800.BIN is entirely filled with FFs. There's nothing there. The VGA card appears to be playing nice here. (That doesn't mean that there isn't some other conflict, but...)

What model is the HDD controller, and can you install it, and run the commands again? C000.BIN should be identical, I'd expect C800.BIN to be different. No need to connect the HDD, just insert the controller.
 
The controller is a Western Digital WD1004A-WX1. It doesn't say Rev. A anywhere on the card, so I assume it's not the Rev. A version. I'll make the new files and send them to you in a bit.
 
That's interesting, because your dump has it at 0xCA000. (ROM appears to end at 0xCBDFB, but then there's 0x00s from 0xCBDFC to 0xCBFA2, then 0xFFs from 0xCBFA3 to 0xCBFFE, and a 0x25 at 0xCBFFF.)

Can you get a high quality photograph of the card? (Good enough to see any designations, as well as current jumper positions.)
 
Oh whoops, I removed the wrong jumper! Do you want another dump at C8000? I'll send you a picture of the card, too.

Edit: Sent you the C8000 dump and a picture of the card.
 
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OK, I'm not seeing anywhere that conflicts are happening on what you sent me, the ROMs are mapping correctly. I haven't actually run the checksum algorithm against it, though.
 
That's very intriguing. Thanks for looking anyway! Yet it works perfectly with the IBM CGA card, and it worked fine with the CGA card it originally shipped with. And it can be used perfectly fine as a floppy-only system. Strange indeed.

Would it be any use to provide you a dump after I get the memory parity error?
 
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