Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cwjcc!hal!ncoast!dchou
From: dchou@NCoast.ORG (David Chou)
Newsgroups: comp.sys.ibm.pc
Subject: IBM-AT BIOS ROMS
Message-ID: <1989Sep19.021545.8110@NCoast.ORG>
Date: 19 Sep 89 02:15:45 GMT
Organization: North Coast Computer Resources
Lines: 18

I have recently tried to update a hard disk in an IBM-AT with a
Miniscribe 3085 and have found that the geometry for this disk is not
in the BIOS tables (only 14 are in the tables).  I prefer not to use
a TSR such as Disk Manager.  Fortunately (or unfortunately) I have a
copy of the IBM AT Tech Reference Manual and have located the disk
geometry tables.  It is therefore possible for me to copy my BIOS ROMS
into 27128 EPROMS and alter one of the existing disk types.  Unfortunately,
I suspect that the BIOS does a checksum on the BIOS ROMS, but cannot
find where it is being done or where the checksum is being performed.
Is there anyone out there who has any information on how this is being
done?  I have already found the code where the system performs checksums
on auxiliary ROMS, but this does not seem applicable for the BIOS ROMS.
Incidentally, the system is one of the original 6MHz ATs with 128K
stacked DRAMS.

Thanks in advance.

David Chou     ncoast!dchou@hal.cwru.edu