H89 CP/M hard-secored boot diskette

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Fri Apr 4 12:35:26 2003

 I guess the next question is, does anyone have the
dumps of these chips or what the new mapping is??
I suspect that there is some remapping of the memory
and some for the I/O. I don't know why it would take
3 chips though. I'll have to dig through my stuff to
find a schematic. I may be able to figure it out from there.

>From: "Patrick Rigney" <patrick_at_evocative.com>
>> > > Tony, out of curiousity, what are your versions of the
>> various PROMs and
>> > > EPROMs at U516, 517, 518, and 520 on your Z90?
>> >
>> > That would involve getting to the Z90, which is not going to be
>> > trivial....
>FYI, I found this while trolling through some links on retroarchive.org.
>Excerpt (edited) from an Arpanet message dated 17-feb-1984:
>"When I ordered CP/M the first time and it didn't work, I called
>Heath and they said "Oh, yeah, you need a hardware upgrade!"
>So I did the following:
>1) Replaced the 444-42 in U517 with a 444-66
>2) Connect a jumper from the middle pin of U503 to pin 17 of P509
>They assured me this would work. However, to make the full upgrade,
>I could also do:
>3) Replace the 444-40 in U518 with a 444-62
>4) Replace the 444-43 in U550 with a 444-61
>If I did this, I would lose cassette capability. Since this wasn't
>necessary (they said) I decided to just do 1 & 2.
>When I did this and it still didn't work, I called Heath again. They
>said it should have worked and my disk must be bad. So they sent me
>a new disk..guess what, still didn't work. Then they say hardware
>problem with the disk drive. That's when I put my problem on the net.
>Mr. D. C. Finch of Phoenix was kind enough to write me a letter
>(they have R/O access to the net) which told me that indeed 3 & 4
>were necessary (at least for CP/M 2.2.03 and later). So this morning
>I called Heath again and they said, "That's right, you have to replace
>all three chips!" Just wish they had said that back in November!!
>I'll be happy to give anyone the details of Mr. Finch's letter if
>asked, I don't think most people are that interested.
Received on Fri Apr 04 2003 - 12:35:26 BST

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