I agree with armor alley. I have installed mac os 8.1 & 9.0. Mac os 8.1 is the best for my performa 6116. Very stable and fast. I have installed the sonnet nubus g3 500mhz and 136mb of ram and the machine flies. Very rarely i use mac os 9.0. Some time before i had installed also mac os 7.6. So fast with the sonnet nubus!!! but I think the best is 8.1 version.