8-bit IDE hard drives, controllers

[Herb Johnson - null account]

Roger Merchberger posted some days ago (I get the digest which is always 
late) in the thread "Wowzers... The things I found... Long!"

 > In other news, I found an 8-bit IBM PC compatible hard drive 
interface > not sure if it's MFM or RLL (they used the same cable set) 
Model
 > number is  WD1002A-WX1 up for grabs. It'll run 2 drives, but I only
 > have a cableset for 1.

That reminds me of recent posts about other 8-bit ISA (IBM PC bus) hard 
drive controllers. Some of the EARLIEST IDE (not MFM) hard drives used 
an 8-bit data bus, not the 16-bit which became standard subsequently. So 
some of the earliest 8-bit ISA IDE controllers and drives are not 
compatible with subsequent drives and controllers. I don't know or 
remember an easy way to determine this, beyond checking the specs of 
drive or controller. There is no difference in the connector.

The conflict might cause damage, so "try and see" is not the best idea.
Fortunately there were not a lot of those drives produced, but it's 
something to consider when restoring systems of the era around the first 
IDE hard drives.

Herb Johnson
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