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Timings?

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Root5098

Member
Joined
Jan 3, 2010
I was wondering, what's the timings on RAM mean?

For example:
Corsair Dominator 1600MHz: JEDEC standard 9-9-9-24 values at 1333MHz.
Corsair XMS3 1600MHz: Latency of 7-7-7-20, 1T for maximum reliability and performance

Why does it say 1333MHz if it's 1600MHz?
What's the difference between 9-9-9-24 and 7-7-7-20?
Which is the best of the two?
 
This article has a pretty good explanation.

http://www.hardwaresecrets.com/article/26

The summary:

* CL: CAS Latency. The time it takes between a command having been sent to the memory and when it begins to reply to it. It is the time it takes between the processor asking for some data from the memory and it returning it.
* tRCD: RAS to CAS Delay. The time it takes between the activation of the line (RAS) and the column (CAS) where the data are stored in the matrix.
* tRP: RAS Precharge. The time it takes between disabling the access to a line of data and the begin of the access the another line of data.
* tRAS: Active to Precharge Delay. How long the memory has to wait until the next access to the memory can be initiated.
* CMD: Command Rate. The time it takes between the memory chip having been activated and when the first command may be sent to the memory. Sometimes this value is not informed. It usually is T1 (1 clock cycle) or T2 (2 clock cycles).
 
The 1333Mhz is the JEDEC standard that the module will default to if you set it to "JEDEC" in bios iirc. It really doesn't matter, just look at what the rated specs at 1600 mhz are if that's what you're looking for. 7-7-7-20 will run faster and have more overclocking headroom than 9-9-9-24 but most of the difference is synthetic and, if you are gaming and not using a bajillion writes/second, you won't notice much of a difference. If the prices are the same, get the lower timing one. But really, I would just go for the cheapest one - then again, I am a broke college student lol.
 
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