How come PC1600 is CAS2 but PC2100 is CAS2.5?

[MichaelD]

I didn't think this was "technical enough" to go in the Highly Technical forum. I was looking at Crucial's site, contemplating buying some DDR now, for a rainy day, when I realized that they don't sell CAS2 PC2100.

Now, from reading here, I already know that Crucial's PC2100 will do CAS2 w/o any problem. Just curious as to the exact reason why. thanks.

 

[bozo1]

Most of us have had no problem doing CAS2 with the Crucial PC2100 but they are not guaranteeing it. I would take that to mean that not every module will do CAS2.

 

[DARRIN]

Mushkin PC2400 is CAS 2. $83 for 256 megs.

 

[Remnant2]

If I recall right from reading the DDR specs, CAS2 1600 and CAS2.5 2100 are effectively the "same" memory, in terms of timing strictness and whatnot. CAS2 2100 is more difficult to achieve, and they probably feel that they don't have the yields yet to be able to produce a high volume of CAS2 parts at the higher frequency.

Why we can all bump the pc2100 to cas2 with no problems is unknown. Probably increased I/O voltages above the minimum/best-case instead of worst-case configurations inside our computers.