SDRAM

[amateur]

128MB PC-133 CAS-2 SDRAM DIMM

wat does "CAS-2" means ? is that the clock ?
is 4-clock sdram faster than 2-clock sdram ?
is there such thing as 3-clock ; i saw CAS-3 though.
i have to know this to decide wat kind of memory
to get for my motherboard.

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by a computer geek wannabe :p

[scada]

CAS stands for "Column access strobe" and is the time it takes to get or read the correct column in a memory bank. This time period is called a "latency" and will be between 2 and 3 cycles. Thus the CAS2 or CAS3 your seeing. CAS2 is faster than CAS3, but unless your really into getting the most performance out of your computer it's really not that big a deal.

There are 4 things that affect the speed of memory banks ( and therefor DIMMS)size of clock cycle (ie: 7ns = 133MHz or 10ns = 100MHz) RAS to CAS delay,CAS, and finaly PRECHARGE TIME.
CAS and clock cycle or "NS" is always talked about and displayed. But RAS to CAS and Precharge time will be numbers you'll have to search for.

Here's the low down. (quick and dirty)
RAS to CAS... the time it takes to read the right row from a memory bank.
CAS....the time it takes to read or get the right column from a memory bank.
PRECHARGE TIME.....the time it takes to write BACK the old information into the row when closing a row to open a new one.

But these are not the only numbers that matter when talking about memory access speed. There are latencies added to some Motherboards to support 2 types of memory. Also there is the time it takes for the CPU to send the request to the chip set and the time it takes for the chip set to send back the info to the CPU.

But for most people CAS is the only "latency" their interested in and the only one you can control to some point.

Hope this helps http://www.PCGuide.com/ubb/smile.gif




[This message has been edited by scada (edited 11-15-2000).]

[Paleo Pete]

Very good scada...

Here's a link to the memory chapter in the PC Guide (http://www.pcguide.com/ref/ram/index.htm) that may have more info that could help.

Kingston Memory (http://www.kingston.com/tools/bits/bit21.asp) also has lots of good info about memory in general.

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