What is the difference between 2-clock and 4-clock memory?
Two types of SDRAM modules are the 2-clock and the 4-clock module. Structurally, they are the same, but they are accessed differently. A 2-clock SDRAM module is set up so that each clock cycle accesses two chips on the module. A 4-clock SDRAM setup accesses 4 chips per clock cycle. To choose what kind to get, you must look into the motherboard's documentation. 4-clock modules are the more commonly used.
The typical indication of the wrong type being used is a system giving error beeps and not booting as it cannot use the memory installed. The system will not proceed past POST (Power On Self Test). 2-clock was only used in 66 MHz systems. All PC 100 and PC 133 memory is 4-clock only.
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