Path: utzoo!mnetor!uunet!husc6!rutgers!mtune!codas!usfvax2!tscs!gerard From: gerard@tscs.UUCP (Stephen M. Gerard) Newsgroups: comp.sys.ibm.pc Subject: Re: Bios upgrade for old AT Message-ID: <182@tscs.UUCP> Date: 10 Mar 88 00:18:24 GMT References: <3903@batcomputer.tn.cornell.edu> Reply-To: gerard@tscs.UUCP (Stephen M. Gerard) Organization: Total Support Computer Systems, Tampa, Florida Lines: 30 Keywords: Low-down underhanded IBM ploy In article <3903@batcomputer.tn.cornell.edu> sparks@tcgould.tn.cornell.edu (Steve Gaarder) writes: >We have an old AT (model 99) which we use as a file server with Novell >Advanced Netware 286. We recently purchased a Miniscribe 40 Meg drive >for it. This drive is, I believe, a type 36. Now we have a problem. >Our machine only supports 4-bit drive types. This, I understand, can >be fixed by upgrading the bios. >So, folks, the question is: what can I do to upgrade my bios? Is there >a way to get the IBM ROMs? Can a buy a Phoenix or other bios that will >work in my AT? Is there a clever hack I can use? If this article appears twice, sorry. Our neighboring site had some news hungar pains, and appears to have eaten this article. You can solve this problem if you have access to an EPROM programmer and two 27256 EPROMs. Basically, you have to pick out a drive table entry that you are not likely to need, and set the values for that entry to values that match your drive. The drive table is composed of sixteen 16 byte entries that specify the number of heads, cylinders, Write Precompensation Cylinder, the landing zone, etc. This table begins at location 0xE401 in the IBM AT BIOS (the BIOS resides in memory at segment offset 0xF000). After changing the drive table, you will have to adjust the checksum byte or else your machine will not be happy with you. :-) If you have access to an EPROM programmer and wish to tackle the project, write me via e-mail and I will tell you the specifics. ------------------------------------------------------------------------------ Stephen Gerard - Total Support Computer Systems - Tampa - (813) 876-5990 UUCP: ...{codas, gatech}!usfvax2!tscs!gerard US-MAIL: Post Office Box 15395 - Tampa, Florida 33684-5395