Been there, done that!
Despite my best efforts, I have not found a resolution to this problem. Other sites list all sorts of fixes but none of them seem to work. My 5000 also has quad P200s, plus 1.2GB Ram, and 120GB HDD available (it was a good deal for $50 AUS!)
FWIW however, I have been able to get RH9 installed on a 2500 (333Mhz, 512MB RAM) without any problems at all - RH8 did NOT work on this same box.
From my web-trawling so far, it appears to be a combination of the parameters for the SCSI card, and the BIOS. Unfortunately, I don't have the knowledge to solve this one. Maybe there are some other, more clever people, who can run with this and find a solution.