Memory Timings.... again

[stan03]

In the bios these are the settings
Cas 2.5
Precharge 6
Ras to Cas 3
Ras Precharge 2
Refresh mode 7.805

what is refresh mode.... and are those good timings? if i want to lower them which one(s) should i lower for better performance? its running at stock speeds and stock voltage also

[batboy]

Those aren't too bad of timings. I'd try Cas 2 first, that'll give you your best performance. If that works, maybe try precharge at 5. Might have to bump up the vmem a notch to stay stable with more aggressive timings.

[JKeefe]

The holy grail of timings is 2-5-2-2, in the order that you list them. You should lower all of them for better performance, but of course that can couse instability and POST failure. CAS will help the most, as batboy said.

If you have Corsair 3200LL like it says in your sig, then the rated timings for that memory are 2-6-3-2 @ 2.75V of Vdimm. If you can hit those at DDR400 then you are getting what you payed for. Note the higher recommended voltage. If you can't get those timings and speed stable, then get in touch with Corsair.

[stan03]

..... the rated timings. does that mean what it is supposed to run? or the stock speeds? if its stock then why does my mobo run it at CAS2.5?

[stan03]

ok so now im here with CAS 2, i tried setting it at 2-6-2-2, but even at 2.8 volts (the max for my board) i couldn't get into windows... is there something else i could try....?

and ummm how do you use memtest 86(the dos version )?:o, are you supposed to unzip it first? could someone just give the the steps? thanks. (i hardly know how to use dos :()

EDIT: ahhhh, i scored lower with sandra with cas 2 settings.... did i do something wrong? i only get a bandwith of about 4417....

[JKeefe]

Rated timings are the minimum timings that the memory is advertised to run at. The reason that your board defaults to higher timings is something called SPD. SPD stands for serial presence detect, and is encoded on your memory modules. The SPD is set higher than the rated minimum so that the memory is guaranteed to work with all motherboards without instability. I beleive SPD on your sticks is 2.5-8-3-3; I could be wrong, but it doesn't really matter.

So, "stock" is a tricky term with memory timings. The stock speed is obvious, but terms like stock timings can be confusing, and refering to SPD timings or rated timings can eliminate that confusion.


To use Memtest86, download the zip file from the website. There is an iso file in that zip - extract it. Then, instruct your CD burning software to burn from an image, and select the iso file. After that, you should have a bootable CD that boots straight to memtest. No knowledge of DOS necessary.


You shouldn't be getting lower SANDRA scores with tighter timings. Make sure you didn't change any other timings. Also, see if you get the same scores by setting the SPD timings manually that you get when you enable SPD.

[vejita-sama]

Newbie question - Can I assume that as long as I post, can boot into winXP and pass memtest; that it's ok to tighten my timings. That is it doesn't 'hurt' the ram to run at 2-2-2-5 if my system is stable but it's rated at 2.5-3-3-6?

Also where can somone look up the SPD timings of different chips? Is there a reference somewhere. Kind of OT but I see people talking about the stock freq/multipler and voltage for CPUs and wonder the samething. Because as I look around AMD's site I can't find those numbers :)

[stan03]

i doubt you will hurt your ram, your computer just won't post

[vejita-sama]

Thanks. I'm about to attempt my first OC as soon as all the pieces arrive (FedEx tracking is odd, shows left ramp in Seattle this mourning but deleviery is not until wed, might try to pickup from airport).

Just trying to get as MUCH information as possible prior. I use to be into comptuers but haven't for a few years. I've learned more about my current (and future) PC in the last 1.5wks here then I would have thought possible. Great site.

[stan03]

http://www.geocities.com/stan030303/Mem.jpg

see anything wrong

[stan03]

now with timings of 2-3-2-5 i get 4463mb/s according to sandra... seems very low.... any recommendations on what to do?

[stan03]

bump

[R4z0r4mu5 Pr|m3]

according to mushkin, the best timings should be 2-2-2-6, tRas shouldn't be lower than tRCD+CAS+2 which then = 6 at minimum

from the mushkin site:

"the minimum tRAS would be tRCD+CAS latency + 2 cycles (to output the first burst of four and make way for the second burst in the output buffers).
Any tRAS setting lower tRCD + CAS + 2 cycles will allow the memory controller to close the page “in your face!” over and again and that will cause a performance hit because of a truncated transfer that needs to be repeated. Along with those hassles comes the self-explanatory risk for data corruption. That one is not a real problem as long as the system is kept running but in case it is shut down and the memory content is written back to the hard disk drive, the consequences can be catastrophic. For the drive, that is. "

i've also read from the mushkin forums that the admins there have noticed data corruption when tRAS has been set lower than 6

[stan03]

are you saying that i should set timings at 2-3-2-6?

[stan03]

as a bump and another question, do you have any idea why memtest runs withough errors yet i can't boot into windows...?

[R4z0r4mu5 Pr|m3]

if you have tRCD = 2 and CAS = 2, then you should set tRAS to 6, if tRCD = 3 and CAS = 2, then you should set tRAS to 7

memtest tests your memory, your motherboard may not be able to handle the fsb you set it to, or your harddrive can possibly be corrupted

[stan03]

its not the hdd im pretty sure cause when i set the mem and cpu to stock speeds its ok. i odn't think its the cpu because i can boot into windows at 230 and run prime just fine if i use the 5:4 divider.... so i should use these timings 2-3-2-7? i thought it was supposed to be 2-3-2-6...

[R4z0r4mu5 Pr|m3]

what is your tRCD?

take that, add 2 for CAS-2, add another 2 clock cycles == what your tRAS should be

[JKeefe]

Just because it's supposed to work at 2-3-2-6 doesn't mean it will. Can you boot and run Prime at 2-3-3-6? 2.5-3-3-6? You need to find out what specific setting is causing instability, then seek to eliminate it or concede to a higher setting.

You will not hurt anything running memory at low latenices. Short of snapping the module in half, overvolting it is the only thing that can hurt it, and even that needs to be very extreme (i.e. 3.2 - 3.4 volts).

[stan03]

i can try when i get home, but i can only set my memory to 2.8 volts anyway.

[R4z0r4mu5 Pr|m3]

if not CAS, then tRP is the most likely suspect that doesn't like too low of timings

good luck

[stan03]

ok i cant do 207 fsb with timings of 2-3-2-6... so what should i try next?

[N803]

In support of Mushkin's statement I have actually measured in Sandra a slight but noticeable higher BW using 2-3-2-7 rather than 2-3-2-6, everything else equal.

[stan03]

higher BW? whats BW? :o

[N803]

BW=Bandwidth ;)
I used Sandra's Memory Bandwidth benchmark for the test.

[g0ldberg]

great thread .. thanks a bunch :)

[stan03]

if i run 2-3-2-7 do you think i can get a higher overclock?

[JKeefe]

Maybe - try it and see; only you will know