[sebhc] h17 and h8d disk images

Barry Watzman Watzman at neo.rr.com
Wed Sep 1 20:44:11 CDT 2004

I may be having a "bad memory day" -- it's been 20 years, after all --, but
that's not my recollection.  The Microsoft stuff for HDOS, of course, only
worked under HDOS.  For CP/M there was a "vendor" byte in the CP/M serial
number that an applications program could check, and all of the Microsoft
software for CP/M (sold by Heath) did check that and wouldn't run unless it
had one of {I think} 3 values, the values assigned to Lifeboat (which sold
CP/M for Heath systems, for a while), Heathkit and Zenith Data Systems.

But I don't believe that we played any games with the memory mapping in any
of the software that I was responsible for (which was all of the systems
software under CP/M for the H-8 and H-89).

-----Original Message-----
From: sebhc at sebhc.org [mailto:sebhc at sebhc.org] On Behalf Of Dan Lanciani
Sent: Wednesday, September 01, 2004 9:31 PM
To: sebhc at sebhc.org
Subject: Re: [sebhc] h17 and h8d disk images

Dave Dunfield <dave04a at dunfield.com> wrote:

|Does anyone know if CP/M just switches to RAM once, or does
|it toggle between ROM and RAM (say to access ROM functions)?

The operating system proper just switches to RAM; however, various
CP/M applications sold by Heath were buggered to work only on Heath
hardware.  They did this by switching the ROM back in and checking
for some known bytes.  I have a vague memory that something that came
with the OS did this as well.

				Dan Lanciani
				ddl at danlan.*com
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