Some chipsets are flakey at the higher IDE bus speeds (VIA). There are fixed chipsets that identify themselves the same as the broken parts. It is a case of defaulting to the safest setting, while allowing the admin to change the setting if he knows he has the fixed chipset.

>Hi Arthur,
>
>I rebooted my system yesterday, and when prompted by RedHat as to which operating system to boot, I did a cntl+D to the command line an entered Linux append="idebus=100". The system booted without any complaints. When I checked my message file it had the same assume 33Mz statement in it as before, so what I was trying to do didn't work.
>
>I really don't know why Linux put the assume statement in, but it may be that probing the ide bus is dangerous and could damage your hardware. On must motherboard the bus speed is set by configuring a jumper and I don't think the operating system can override this. So I'm not convensed that the assume line in the bootup message file has anything to do with actual speed the hardware is using. The message file indicates the system detects my 500 Mz cpu just fine, and it detects my two hard drives as UMDA 100 Mz 60 Gig and 40 Gig just fine. Perhaps it would be wise to follow the advice I have often seen posted of “if it ain't broke, don’t try and fix it”.