How important is CAS?

[slade8200]

I'm planning on get 3x2GB for a new PC setup. I plan on doing some gaming (should I only need 4GB?). Should I stay away from CAS 8 & 9 and only be looking at 6 or 7? I'm looking at DDR3-1600.

 

[CurseTheSky]

Unless you're doing a lot of hardcore overclocking, DDR3 speeds and CAS latencies mean very little these days. In fact, they haven't meant much since the Athlon 64 days where your overclock and overall performance depended a lot on your memory's ability to take voltage and translate it into higher frequencies and tight timings.

Let's put it this way: if you're spending less than $60-70 on your CPU's heatsink or other cooling method, you're probably fine with the cheapest set of (reliable) DDR-1333 you can find.

 

[taltamir]

I'm planning on get 3x2GB for a new PC setup. I plan on doing some gaming (should I only need 4GB?). Should I stay away from CAS 8 & 9 and only be looking at 6 or 7? I'm looking at DDR3-1600.

you will get about 1 to 3% average performance improvement in most app per each step, aka... 9 to 8 cas yields about 1 to 3%, etc...
That is assuming that the ram is otherwise perfectly identical.
Also, some apps will get 0% improvement or more than 3% improvement, but in general you will see around 1 to 3% difference in most cases, with most being closer to the 1% IIRC.

 

[slade8200]

Well hopefully I will be able to a some overclocking. I'm going to have an ASUS board with an i7-950 and a Xigmatek Dark Knight CPU cooler. I wouldn't be trying to achieve crazy speeds, but it seems things should be quite stable at DDR3-1600. I just wanted to make sure the games with run real nice.

 

[fluffmonster]

The frequency of the ram won't matter unless your mobo uses it. skt1366 defaults at 1066. ddr3-1333 is at its stock frequency with a mild overclock (bclk 166 with a memory multi of 8). ddr3-1600 will allow you to push further just fine. I wouldn't worry about latency, you won't notice it. Don't get anything that needs more than 1.65v though.

 

[slade8200]

So if I buy DDR3-1600 memory and put it in, and all the BIOS stuff is set to auto (or default), it will run by default at 1066?? Also, when buying the memory should I only check out the 1.5V stuff and not the 1.65V. Thanks.

 

[fffblackmage]

So if I buy DDR3-1600 memory and put it in, and all the BIOS stuff is set to auto (or default), it will run by default at 1066?? Also, when buying the memory should I only check out the 1.5V stuff and not the 1.65V. Thanks.

I would recommend going with the 1.5V kits.

 

[fluffmonster]

So if I buy DDR3-1600 memory and put it in, and all the BIOS stuff is set to auto (or default), it will run by default at 1066??

That's right. i7 x58 boards have a system baseclock (bclk) which sets the heartbeat for everything else, and everything else runs at a speed based on its own multiplier. i7-950 has a maximum memory multiplier of x8 and a stock bclk of 133 which is 1066. With a locked cpu multiplier, overclocking this chip means increasing the bclk.

You could go with 1333 ram and still get a pretty good overclock. A 166 bclk (so mild an oc that you should just assume it will be stable) will get you 3.82GHz which is pretty good and do so running 1333 ram at stock freq. Its also generally cheaper than 1600 and a lot easier to find at 1.5v. Note: if you do oc, do not let your mobo set voltages at auto...sometimes the get a little aggressive with the voltages. Best to manually set voltages.

A lot of people do use 1.65v on x58 boards, but that's the max of what intel suggests and spec is 1.5v. I can't give a good assessment of the risks of using 1.65v ram.

 

[Ben90]

I believe the max memory multiplier is 12x

 

[fluffmonster]

I believe the max memory multiplier is 12x

I stand corrected.