but yea my comp has a voodoo5500 agp....but dont know what mandrake 8.1 is...so that can suck... but i can tell you that 3dfx went out of business and a ton of new software no longer support that hardware...gay aint it... i feel ur pain..
oh and I really can't help you. I myself have had tons of problems getting certain hardware to work for linux. I dunno..learn some C/ASM and code your own drivers LOL