Greg Easthom wrote in a message to Wayne Chirnside:

 GE> The typical indication of the wrong type being used is a system
 GE> giving error beeps and not booting as it cannot use the memory
 GE> installed. The system will not proceed past POST (Power On Self
 GE> Test). 2-clock was only used in 66 MHz systems. All PC 100 and PC
 GE> 133 memory is 4-clock only. 

Which doesn't *quite* say that a 66 MHz system needs the 2-clock variety, 
only that it might.  Is there any easy way to tell?

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