[comp.sys.ibm.pc.hardware] help with AT ROM BIOS required again

geoff@sheoak.bcae (geoff) (08/15/90)

 post2 , hello all   
 last week i asked about reworking the checksum in
an AMI on PHNIX BIOS ROM for an AT. 
 the responce i got was to add all bytes , MOD 256
and change any un-used byte to finish up with ZERO.
my question is :  is this the same as an 8 bit add
                  of all bytes =ing 00.
if so Y dont any of the BIOSes we have add up to
00 or N*256  eg 15A70
 
thanx again JEFF