H89 CP/M hard-secored boot diskette

From: Patrick Rigney <patrick_at_evocative.com>
Date: Thu Apr 3 17:48:01 2003

> The Z90 is built to be 64K a H89 isn't. As far
> as I recall, the H89 took more than a simple jumper or
> switch to make it CP/M compatable.
> Also, one should note that HDOS came in both hard and soft sectored.
> Dwight

Dwight, I think you're right. Address decode is controlled by U516 and U517
on the CPU board... and those are PROMs of Heath's creation... close to
unobtainium. I have several different versions of each of these PROMs, but
I haven't yet figured out their contents and differences.

Oh, and regarding my earlier comment about the MTR EPROM... I went back and
looked at my old emails, and apparently there's more to the MTR-90 ROM
version story. You can use either 444-142 *or* 444-84 with the soft-sector
controller. Version 444-142 is reported to support both 40 and 80 track
drives; 444-84 supports only 40 track drives.

Tony, out of curiousity, what are your versions of the various PROMs and
EPROMs at U516, 517, 518, and 520 on your Z90?

Patrick
Received on Thu Apr 03 2003 - 17:48:01 BST