The RAM expansion modules for the iMac are 168-pin SDRAM DIMMs that are 3.3 volt, unbuffered, 8-byte, non-parity, and PC-100 compliant. The speed of the SDRAM devices must be rated at 125 MHz (8 ns) or faster.
IMPORTANT
RAM expansion DIMMs for the iMac must be PC-100 compliant and use SDRAM devices. If the user installs a DIMM that uses EDO or SGRAM devices, the computer will beep several times when the user attempts to restart the computer.