The Power Mac G4 computer uses PC100 compliant, 168-pin SDRAM DIMMs. The mechanical characteristics of the DIMM are given in the JEDEC specification for the 168-pin 8-byte DRAM DIMM. The specification number is JEDEC MO-161; the specification is available from the Electronics Industry Association's website at
http://www.jedec.org/download/pub95/
The electrical characteristics of the DIMM are given in section 4.5.6 of the JEDEC Standard 21-C, release 7. The specification is available from the Electronics Industry Association's website at
http://www.jedec.org/download/pub21/
The RAM DIMMs are required to be PC100 compliant. The PC100 specification is available from Intel's website at
http://developer.intel.com/design/chipsets/memory/sdram.htm#S1