Double-sided RAM cards should pose no problem, as that implies low-density chips as the CRT iMacs need, The specification, which you may not have if you were not aware that you needed it, is 168-pin, 3.3-V, PC-100, non-ECC, unbuffered, unregistered, low-density SDRAM, with no more than 16 chips per card, and no more than 512MB per slot.

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