Memory Latency

[BrokenArrow64FX]

I have seen latency numbers next to different types of RAM? like 3-4-4-8

what do these numbers mean?
is 3-4-4-8 good?

 

[JBT]

Well with memory latency the lower the better. 3-4-4-8 is not very good something like 2-3-2-6 or something are ussually good numbers but as the speed of memory goes up latencies in the real world seem to affect performance less and less.

The first number 3 refers to the CAS which is the most imporant of the timmings and affect performance the most.

The first 4 refers to RAS to CAS and does affect performance too but in the last couple of months most RAM manufactures have not been able to produce memory that ran at 2-2-2 but they can run at 2-3-2.
Anyways it seems Mushkin is staring to get some more in that does all two's for PC3200 atleast.

The Next latency is RAS precharge also affect performance and lower is also better.

The last latency TRas ( I forget what it stands for) seems to be better when in the about 9-12 11 seems to be best though on Athlon Systems atleast on Nforce 2 +3 boards. For Intel and Athlon Systems with Via chipsets lower is better but the general rule of thumb would be CAS, + RAS to CAS, + 2

Example CAS 2 + RAS to CAS 3 + 2 = 7

If you have any more questions feel free to ask or if anyone has any corrections or changes no problem.

 

[BrokenArrow64FX]

i forget where but i remember seeing memory with a 2-2-2-10 latency
good no?

 

[JBT]

Instesting I have never seen such a thing at stock settings but you can change the settings in the bios of pretty much all Overclocking motherboards anyways.

I run mine at 2.5,2,2,11 as you can see.

 

[edmundoab]

Originally posted by: BrokenArrow64FX
i forget where but i remember seeing memory with a 2-2-2-10 latency
good no?

I believe that is the optimization for dual channel Nforce 2
the timings are set to 2-2-2-11

But normally by SPD, the mem timings are rated 2-2-2-5

Yes, 3-4-4-8 are relax timings at CAS 3. Companies like Corsair, Mushkin and Kingston do that to allow these memories to be very overclockable, ie. PC 4000, PC 4200 and so on..

premium timings should be at 2-2-2 of course they come with a price.

 

[BrokenArrow64FX]

yeah i saw those timeings on the Corsair XMS mem the dual channell 1024 DDR550 to be exact.

 

[Ages120]

OCZ Enhanced bandwidth ram can out pace memory with lower timings. I have some Kingston generic ram running at 2-2-2-6 1t at 2.8v and I get another 150mbs then the default 2.5-3-3-7. Helps if you can find out the chip model used on the board although some manufacturers can get better timings out of ram by enhancing thier pcb.

http://www.obm.co.nz/guides/overclocking/speedupddr.htm this gives some good info about ddr although I would research a lot before you attempt to tighten up your timings or overclock.