Daybreak hard drives (was Re: Collectibles for the future)

From: Eric Smith <eric_at_brouhaha.com>
Date: Wed Nov 11 18:22:40 1998

Tony wrote:
> If it's a Daybreak, then I've got a pinout of the hard disk module
> connector (module C8), so you can try putting in a normal ST506 drive.

If it's not already on the web somewhere, please send it to me, and I'll
add it to my retrocomputing pages. I didn't get a C8 with my 6085, so
I could certainly use this info.

I've been thinking about designing an interface card to replace ST-506
interface drives with ATA (IDE) drives. It's getting hard to find
Maxtor 2190s at a decent price, and I'm not sure how many more years it
will be possible to keep them running at all.

The basic concept would be to simply sample the MFM (or RLL) channel
code at somewhere around 50 MHz as it is being written, and store the
data on the ATA drive. The interface would keep one track buffered in
RAM. Whenever the host requests a head change or seek, the buffer would
be written to the ATA drive (if it is dirty), and reloaded with the data
for the new track.

This would require a much larger ATA drive than the original drive it is
emulating, 102K bytes per track. To emulate a Maxtor 2190, this requires a 2G
ATA drive. You could even emulate drives larger than that by emulating more
cylinders.

The tricky part is that it might be necessary for the simulated drive
to mimic the effect that write precompensation in the host's controller
is intended to circumvent.
Received on Wed Nov 11 1998 - 18:22:40 GMT