DDR3 1333 or 1600

11 Aug 2003
Taunton, Somerset
I have been procrastinating for ages about a new system and believe it or not I still have some things I would like your opinions on............

I'm almost sure I'm going to go for the i7 920 I will start off with 6GB and possibly increase this to 12GB when I can afford it. I will be over clocking but I don't want to push it as far as 4GHz as I have concerns over the high temperatures involved. I've been looking around on the internet Linky and it seems that if I choose to over clock to 3.5GHz then DDR3 1333 would be up to the job. Is it worth going to 1600 or would it just be a waist of money - your thoughts please
8 Oct 2008
In Lockdown England
I would say for the closeness in price , the 1600 would be a good investment. When over-clocking the ram is usually the first thing to cause problems. As you said 1333 will be fine upto 3.5 / 3.6 but its if you ever want more than that. But as of stock there pretty much the same in the real world , just nicer to have some head room wouldn't you say.

With the i7 you would need a sufficient cooler in any case to overclock to a noticeable level. The cooler you would need ( eg - true , Pro mag , Noctua ) should be able to achieve pretty much the same temps at 3.6 - 4ghz give or take 3degs here or there. So going to 4ghz will not always be that much warmer.

19 May 2004
Horsham, West Sussex
I've been doing research on this.

It seems that running 1600 at a higher CAS (CL8 or 9) pretty much eliminates the speed gain over 1333 at a lower CAS (CL6 or CL7).

What I find frustrating though is that none manufacturers provide SPD information for their RAM.

I guess that most 1600 RAM at CL8 or CL9 will happily run at CL6 or CL7 when underclocked at 1333, but unless you can find a specific review, test or comment for that RAM it is very difficult to know for sure.

My gut feel would be to buy 1600 and then run at 1333 with lower CL - that way you have the flexibility of running at higher speeds if you are able.

My frustration is it is almost impossible to know for sure what any particular non-1333 RAM will do at 1333 because they don't publish the SPDs.

At the moment I just ordered some 1333 with stated CL7 but I'm not confident that was the best choice.

The other thing, is don't forget that the CAS spec is a little artificial because it is quoted in number of clock cycles, but when you compare RAM of different speeds then the size of their clock cycles are different.

For example

CL9 at 1600 = 5.6nS
CL8 at 1600 = 5.0nS
CL7 at 1333 = 5.25nS
CL6 at 1333 = 4.5nS

CL5 at 1066 = 4.7nS
CL4 at 800 = 5nS

So you see, although it looks like CAS is getting bigger it isn't really if you express it in absolute terms.

Having said that there will be little difference in performance between CL7 1333 and CL9 1600, or CL6 133 and CL8 1600.


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