Bandwidth vs. Cas Latency

[Zero001]

- Which is more important when considering the purchase of RAM?
For example: is DDR2 800 (PC26400) with CAS 3 faster than DDR2 1066 (PC2 8500) with CAS 5?

- Is there a formula to determind how much more bandwidth you need to make up for the lost of CAS latency?

- Does one have more importance than the other when overclocking?

 

[Shimmishim]

I think this is a great question but difficult to answer.

The best way to find out would be to run some tests...

picking an arbitrary clockspeed of.... 3200 let's say...

someone should test 6 x 533 cas 5-5-5 vs. 8 x 400 cas 3-3-3.

anyone up for the challenge?

I'd like to know the results myself!

 

[CalvinHobbes]

Didn't Anandtech do a test just like this recently?

I'm pretty sure some other sites have as well.

 

[tersome]

Originally posted by: Shimmishim
I think this is a great question but difficult to answer.

The best way to find out would be to run some tests...

picking an arbitrary clockspeed of.... 3200 let's say...

someone should test 6 x 533 cas 5-5-5 vs. 8 x 400 cas 3-3-3.

anyone up for the challenge?

I'd like to know the results myself!

Sure. I'll test it.

8x 400mhz 3-3-3-8 gives me 13549 in 3dmark05.

http://img293.imageshack.us/img293/982/untitled1ks1.jpg

6x 533mhz 5-5-5-15 gives me 13630 in 3dmark05.

http://img295.imageshack.us/img295/7258/untitled2vt9.jpg

Less than 100 points difference :roll:. I'd just get whatever is cheaper.

 

[n7]

Tests have already been done that pretty much sum it up.

Bandwidth is more important than timings except on the nForce chipset when 1T is used.

I did some testing here too.
http://forums.anandtech.com/messageview.aspx?catid=28&threadid=1971132

 

[lopri]

I haven't bought memory for some time but I'd get the DDR2-800 CAS 3 sticks over DDR2-1066 CAS 5 sticks if they are at the same price. It is not because of the performance difference between the two but because I'd think the former would be somewhat more flexible than the latter. (Note: Assuming both are Micron D9) It is also a good practice to check the stock voltage for the rated frequency/timing. Of course the lower the better. But the truth is, most name-brand micron D9 sticks behave similarly. Look for a deal and go with less expensive ones with a good warranty.

 

[theangel24]

even for nforce on 680is, bandwidth is more important. 5-5-5-15 1066 runs faster than 4-4-4-12 800