I'm confused.....

So, a RAM stick that has a lower cas latency is better, right? Then, why do older types of RAM have a lower cas latency and newer types of RAM have a higher cas latency?:confused

could someone please explain? thanks!

 

Sometimes memory also has a specification such as CL2 or CL2.5, which refers to the CAS latency rating of the ram. The smaller the faster.

SDRAM comes with latency ratings or "CAS (Column Address Strobe) latency" ratings. Standard PC100 / PC133 SDRAM comes in CAS 2 or CAS 3 speed ratings. The lower latency of CAS 2 memory will give you more performance. It also costs a bit more, but it's worth it.
CL or "CAS latency," which is the number of clock cycles it takes before data starts to flow once a command is received. Low CAS latency is faster than high CAS latency. However, faster memory will NOT necessarily make your system faster. Your computer will only run as fast as the "slowest link" in your system, so you can't speed up your computer by adding memory that is faster than your current memory. The way to make your system faster is to add more megabytes (MB) of memory.

If you're building your own system, then use parts with low CAS latency.
DDR memory comes in CL 2 and CL 2.5 ratings, with CL 2 costing more and performing better.
A CAS latency of 2 is pretty much standard for most of the older PC133 memory. A CAS latency of 2.5 is pretty much the standard for most of the DDR PC2100,PC3200 memory.

From here: http://www.mpasystems.com.au/cgi-bin/mpa.pl?04_support+89_RAM Explained

 

um, thanks, but thats not really what my question was...

my question was, why do older types of RAM (DDR) have lower CAS latency than newer types of RAM (DDR2, DDR3)?

i noticed that older types of RAM usually have CAS latency numbers around 2.5 or 2, and newer types of RAM have CAS latency numbers around 4-6? wouldn't it make more sense to keep the CAS latency numbers lower (in the 2's and 3's) instead of raising them as technology progresses?

 

CAS latency is over-rated in how important it is. It refers only to the first burst of data in the entire clock cycle, it does not affect the following ones at all. Clock speed is far more important to RAM speed than CAS latency.

As for why it is higher in newer RAM, it is because higher clock speeds need higher latencies to be stable (note this explanation is greatly over-simplified). And since newer memory, DDR2 and DDR3, come in higher clock speeds, the latency is higher by default. The newer memory is still faster, proving my earlier point about clock speed being more important.

 

thanks, im not confused anymore