news@hagbard.dc.luth.se (news) (10/03/90)
Hi, I made a copy of my bios (eprom copy) with the intention of adding some additional hard drives to the drive table. There are only 10 bytes of extra code in the new bios, but it just won't boot the computer! Why ? Is there some kind of checksum in the code some were ? or what ? I would like to get the computer running as quick as possible. Any kind of help or hint would be appreciated. Use email. Thanx, /Ingvar (ingsa@ext.luth.se)
james@bigtex.cactus.org (James Van Artsdalen) (10/03/90)
In <1518@hagbard.dc.luth.se>, news@hagbard.dc.luth.se (news) wrote: > I made a copy of my bios (eprom copy) with the intention of adding some > additional hard drives to the drive table. > There are only 10 bytes of extra code in the new bios, > but it just won't boot the computer! Why ? > Is there some kind of checksum in the code some were ? Probably. First find out what the checksum of the original ROM(s) were. It's probably zero. In any case, you need to make the new checksum the same. If you have a 16 bit wide BIOS, it's possible that both ROMs need to have the right checksum. Find one or two unused bytes in the ROM reasonably near the bytes you changed (ie, within the same half of the ROM). It's quite likely that there are lots of unused areas in the last 8K of ROM. Just arrange for the values in those two bytes to cause the overall checksum(s) to be the same. If someone used a CRC or 16 bit checksum, the problem may be harder. -- James R. Van Artsdalen james@bigtex.cactus.org "Live Free or Die" Dell Computer Co 9505 Arboretum Blvd Austin TX 78759 512-338-8789
thoger@solan1.solan.unit.no (Terje Th|gersen) (10/03/90)
In article <1518@hagbard.dc.luth.se>, news@hagbard.dc.luth.se (news) writes: |> Hi, |> I made a copy of my bios (eprom copy) with the intention of adding some |> additional hard drives to the drive table. |> There are only 10 bytes of extra code in the new bios, |> but it just won't boot the computer! Why ? |> Is there some kind of checksum in the code some were ? or what ? |> I would like to get the computer running as quick as possible. |> Any kind of help or hint would be appreciated. |> Use email. |> Thanx, |> |> /Ingvar (ingsa@ext.luth.se) Hello ! There *is* a checksum on the BIOS, although I don't remember how it's calculated. :-) On SIMTEL you'll find a package of ROM utilities, and one of them calculates a correct checksum on your code. The adjustment for the sum is by default done to the last byte. I don't even remeber it's name, but I guess a 'grep ROM SIMIBM.IDX' might do the trick.. -Terje