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hw importent is the CAS latency?

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Zoltrix!

Registered
Joined
Jul 25, 2002
I looked over all of the cas latency in diffrent productes.

I know the best latecny is cas 2-2-2-? (the best i sow was 5)

and i have to ask what is the diffrence in prefformens... may i get 100 pointes less if my cas is 2.5-3-3-6 and not 2-2-2-5 in pcmark?


how whould i fell the diffrence?
and i know i can change my latecny to more aggresive, but them i cant raise the fsb much... (or i'm just talking non-sense...)
i nedd some 1 to explane me!!!


thanks! ;)
 

JigPu

Inactive Pokémon Moderator
Joined
Jun 20, 2001
Location
Vancouver, WA
The CAS latency makes a fair amout of diffrence on memory speed. I don't benchmark my RAM (too busy running SETI :D) so I don't know how big the diffrence will be, but it should be at least noticible in the benchmark.

You can't raise your FSB as high when you have your CAS latency at 2 because by lowering the CAS latency you increase how fast the data comes out of memory (just like raising FSB does). So, you can opt for high FSB and high CAS, or low FSB and low CAS.

I personally would go for the lower CAS unless you are trying to make a big overclock without regard to the benifit from lowerd CAS latency or if you are running stuff that is more CPU intensive than memory intensive (where a FSB overclock would help). But I find that usually the lower CAS is faster even with the slower CPU.

JigPu
 

OC-Master

Member
Joined
Jul 14, 2001
Location
Edmonton, Alberta
Like I said in another post, I'd rather have my ram run at 200MHz with relaxed timings rather than have it run at 166MHz with aggressive timings. The trade off of the relaxed timings is made up in MHz both on the ram and on the FSB.


OC-Master
 

deathstar13

FSB FRIEK
Joined
Dec 24, 2001
oc-master is correct again. i think im just following him around to check out the chick-o-the-day.

but anyways jigpu is kinda right.C2 is faster than C2.5.
but higher fsb speeds always outwiegh cas settings.
a lower cas might net u 100-150 pionts in bandwith benchmarks.

but a higher fsb @C2.5 can gain you 800-1000 points just depending on how high u set the fsb.
to sum it up cas ratings is just a fine tuning.it has some gain to it.but higher fsb speeds are way more benificial than running fast timings.
 

Hamburger

Registered
Joined
Nov 9, 2002
Intel systems usually fair alot better with lower timings because they cannot be unlocked and the divider changed, hence FSB usually wont go very high because of the limitations of the CPU itself. So , in saying that, lower more aggressive timings will increase performance.

However on AMD rigs its totally the opposite if you unlock them the sky is the limit with your FSB ,so higher, more stable timings play an important role.
 

PhobMX

Member
Joined
Jun 27, 2002
Location
Toronto, ON, Canada
let me get this straight, im about to buy a corsair xms 512mb @ cas2 stick and an unlocking kit so i can crank the fsb to 200Mhz in my Asus a7v333 mobo to take full advantage of the memory. The fsb is still high and corsair is guaranteed to run at cas2 400MHz, so wheres the drawback? northbridge cooling?
 

jlin453

Member
Joined
Sep 18, 2002
Location
Austin, Texas
PhobMX said:
let me get this straight, im about to buy a corsair xms 512mb @ cas2 stick and an unlocking kit so i can crank the fsb to 200Mhz in my Asus a7v333 mobo to take full advantage of the memory. The fsb is still high and corsair is guaranteed to run at cas2 400MHz, so wheres the drawback? northbridge cooling?

Yeah, I've always wondered if the Corsar XMS cas2 rams could overclock to a high fsb, since the general consensus is the lower the cs setting,the better.
 

deeppow

Senior Member
Joined
May 10, 2002
Location
Los Alamos, NM
My mobo bios are in the following order:
CAS, TRP, TRAS, TRED, Command Rate (CR)
and I'm running 2, 2, 6, 2, 2T respectively. These are the fastest settings for me. See sig below for my system.

Here are the percentages of improved performance compared to the other setting available.
CAS: a setting of 2 is 0.89% faster than a setting of 2.5
TRP: a setting of 2 is 2.29% faster than a setting of 3
TRAS: a setting of 6 is 0.21% faster than a setting of 5
TRED: a setting of 2 is 3.50% faster than a setting of 3
CR: a settting of 2T is 2.68% faster than a setting of 1T

My results are different than normally quoted for TRAS and CR, i.e. that lower is better. On my system this is not the case and I see improved performance with higher settings. That is true whether I run 1 stick or 2 sticks of memory. I ran about 10 benchmarks of Prime95 for each of the above results so they reflect an average of those 10 tests for each percentage quoted.

Test your memory and settings. :cool:
 

cack01

Member
Joined
Mar 7, 2002
Location
San diego or UC Davis
Basically you can look at it this way. Raising the FSB will widen the highway. While lowering the CAS will make the cars go faster. I would rather have a wide highway with medium speed cars then a narrow speed highway with fast cars.

There is a happy medium out there, all you have to do is find it.
 

john240sx

Member
Joined
Jun 22, 2002
Location
Sterling IL
PhobMX said:
let me get this straight, im about to buy a corsair xms 512mb @ cas2 stick and an unlocking kit so i can crank the fsb to 200Mhz in my Asus a7v333 mobo to take full advantage of the memory. The fsb is still high and corsair is guaranteed to run at cas2 400MHz, so wheres the drawback? northbridge cooling?

the only thing that would hold you back is either the processor or the lack of a higher PCI/AGP divider (ie. 1/6 or 1/7)
 

PhobMX

Member
Joined
Jun 27, 2002
Location
Toronto, ON, Canada
john240sx said:


the only thing that would hold you back is either the processor or the lack of a higher PCI/AGP divider (ie. 1/6 or 1/7)

my mobo only supports up to 1/5, ive booted on it at 160Mhz and 1/4 (40MHz pci) and i had no data corruption. If i can make it up to 200MHz the 1/5 will make the same 40MHz, so the only thing holding me back that high would be the mobo, ive heard that asus ones get unstable at 190+. But as stated ill just give it a try...
 

Stumpjumper5200

Member
Joined
Sep 24, 2002
Location
Best 1/4 Mile Time: 13.57 @ 101.13
[threadjack]

anybody happen to know of an intel board with high agp/pci dividers.......or even an agp/pci lock??? that would be so sweet, since I think either my two sticks of bargain DDR400 or R9700 is holding me back.

btw...cack - I like that analogy

[/threadjack]
 

PhobMX

Member
Joined
Jun 27, 2002
Location
Toronto, ON, Canada
Stumpjumper5200 said:
[threadjack]

anybody happen to know of an intel board with high agp/pci dividers.......or even an agp/pci lock??? that would be so sweet, since I think either my two sticks of bargain DDR400 or R9700 is holding me back.

btw...cack - I like that analogy

[/threadjack]

too jacky for me, i didnt get the point, pls explain...
 

Maxvla

Senior Member
Joined
Jun 26, 2002
Location
OKC
wuzzapiman said:
What about C1.5 @ 400Mhz?
when you find some ram that will do 200mhz cas1.5 you better let me know. :D

i doubt seriously there is any memory on the market that can come even close to that.

my pc3000 will do cas1.5 up to 140mhz but thats it.