For OS 8.5.1, use Apple System Profiler and check ROM rev to be $77D.45f2 or later. Otherwise for OS 8.1 use the manufacturing date August of '98 or earlier. For beige G3 machines earlier than the above, a SILK ROM update will be required.Silk ROM kits (ROM and OS 8.1 CD) can be obtained from Magma, Bit3 or Digidesign.