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Memory Timings on modern ram.

post #1 of 6
Thread Starter 
Hi Guys,
I have returned to overclocking after a year away and something that I have noticed lately is that the Cycle time of ram seems lately to be getting faster and going against what the "old School" route used to suggest when we were tweaking timings.

For example, with a set of 10/10/10 the Cycle time would need to be 30, for pretty obvious reasons. yet on 3 seperate pairs of DDR 3 I have here, the timings are faster.

For example, 9/11/9/27.

Can someone fill me in on what I am missng?
post #2 of 6
What timings are you specifically talking about? What is a "set of 10/10/10"?


The standard timings provided by RAM are CL, tRCD, tRP, and CAS but you just don't add them up to get a cycle time.


http://www.hardcore-games.tk/wp/hw/ram.php

Edited by DuckieHo - 1/7/13 at 11:59am
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post #3 of 6
Thread Starter 
Sorry, I should of course have elaborated.

The initial 3 timings, IE: the tCAS, the tRCD and the tRP are normally equal too or less than the following recharge command. (tRAS)

I just dont understand how the recharge command can be exuctuted faster than the sum of the initial 3?
I obviously have a flaw in my knowledge, I just dont know where it is. Would appreciate the help; and education if you have time mate?
post #4 of 6
I read an ASUS guide for X79 a while ago that mentioned the minimum tRAS value should be CL + tRCD + tRP, but I don't think I've ever seen a DDR3 kit where this is the case with factory settings. It's always lower than that, and often can be lowered quite a bit further. For comparison, I had Dominators rock stable at 9-10-10-14, and am currently running Samsung LP sticks at 9-10-9-20.
I don't know how it works, but CL + tRCD + tRP = tRAS no longer applies, so go nuts. tongue.gif
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post #5 of 6
Quote:
Originally Posted by Stu-Crossfire View Post

Sorry, I should of course have elaborated.
The initial 3 timings, IE: the tCAS, the tRCD and the tRP are normally equal too or less than the following recharge command. (tRAS)
I just dont understand how the recharge command can be exuctuted faster than the sum of the initial 3?
I obviously have a flaw in my knowledge, I just dont know where it is. Would appreciate the help; and education if you have time mate?

Precharge, not recharge.

CAS - tRCD + tRP = tRAS is just a rough guideline. I usually use it with all ranks populated so I don't have to spend entire extra days stress testing (lower settings can introduce very subtle instabilities) for next to zero performance improvement.

The timing is a window. If it's too long everything gets delayed, but too short often still works, because if the window closes, it's just repeated.

The ideal lower end figure, for performance, was usually CAS + tRCD + 2 on DDR, and a few cycles higher on DDR2/3.

I used to run a tRAS of zero on BH-5/CH-5/UTT (in the latter case I usually used 1.5-3-2-0 timings), so it would hammer the precharge attempt every single cycle until it went through. It worked, and was often the fastest option on this memory.
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post #6 of 6
Thread Starter 
Thanks guys, will have a play around. I perhaps just missunderstood what I was reading but it stuck in my head and has always served me well, but getting this stuff to 2400 is proving tricky and has got me wondering again and back on the quest for more up to date knowledge. smile.gif
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