Memory question for i5 build

[philbean]

I've seen a few threads about memory for i5 boards but all start talking about overclocking.

I'm not interested in overclocking I just want 4Gb of DDR3 that I can fit and go.

The board will be either a GA-P55-UD3 or MSI P55-GD65. Leaning towards the MSI at the moment.

Memory's the one thing I really don't 'get'. I know that 1.65 is the max voltage.

Some places I've read that 1333 is the 'stock' speed RAM for these setups whilst others I see 1600 recommended.
Ideally I just want something that I can fit and will work without having to alter memory settings in BIOS.

So 1333 or 1600 ?

[nightkhaos]

You don't overclock RAM. Nor do you "plug it in and go"... what you want, ideally, is an XMP enabled module, that way you can just plug it in, flag XMP on in BIOS, check everything is okay, then go, and it will work right up until the point you want to overclock your processor.

To explain about memory, there are two factors you want to consider, first there is the clock speed, simply put, higher is better, higher means less operations per second. Second is the CAS, or CL, latancy, which is considered the metric for defining how fast the RAM goes. The lower the CAS latancy, the faster the RAM goes. The CAS latancy is how many clocks the RAM needs to do a particular operation.

Combine this together and you can work out the time it takes the RAM module to do a CAS operation, which is as good as any for a benchmark to work with.

The equation you need is ( 1000 / RAM Clock (MHz) ) * CAS Latancy = time per memory operation (nano seconds).

Thus some examples. I recommend 1600Mhz CAS 8, which is ( 1000 / 1600 ) * 8 = 5 ns
The el-cheapo RAM you can get is usally 1333MHz CAS 7, which is ( 1000 / 1333 ) * 7 = 5.25 ns

Now there are two other things to consider, high clock speed, i.e. above 1600MHz RAM, doesn't actually cause as much as an improvement as you would think, instead it causes more heat to be produced by your memory controller, so the maximum you want it about 1600MHz.

The other is voltage. The voltages between your Vcore and DRAM should never exceed 0.7 volts otherwise you will do damage to the RAM modules. For safety reasons manufactures put a recommended voltage on the module, which usally never exceeds 1.65 Vs, and I highly recommend you stick to it.

XMP is a protocol designed to "auto-discover" the properities of your RAM, and is useful because it means you don't need to manually set the timings and voltages on most DRAM modules. I always recommend setting them manually, just in case, but that is more to do with the fact I overclock than anything.

Hope this helps with your questions.

[Phage]

Well, I don't know about Phil, but I'm more educated !

[philbean]

Yeah I am (a bit!)

So a 7-7-7 CAS thingy means its faster than a 9-9-9 CAS thingy yes ??


Will it always say in the specs if the RAM has XMP enabled?
I was looking at this > gskill.com/products.php?index=222 < but it doesn't mention it.

If it does NOT have the XMP enabled does that mean you have to manually set memory settings in BIOS?

[nightkhaos]

Well, I don't know about Phil, but I'm more educated !

I didn't even get into Command Rate stuff, or explaining the different types of Address Strobes...

[nightkhaos]

Yeah I am (a bit!)

So a 7-7-7 CAS thingy means its faster than a 9-9-9 CAS thingy yes ??


Will it always say in the specs if the RAM has XMP enabled?
I was looking at this > gskill.com/products.php?index=222 < but it doesn't mention it.

If it does NOT have the XMP enabled does that mean you have to manually set memory settings in BIOS?

At the same clock speed, CAS 7 is faster than CAS 9, yes.

As for XMP enabled, it won't always be, but if it's a named brand it's a fair bet it will be. And manually setting memory timings isn't that hard. There's a wee blurb about it in my Bloomfield Overclocking Guide... someone really needs to write a Lynnfield guide.

[Phage]

I didn't even get into Command Rate stuff, or explaining the different types of Address Strobes...

Probably a good thing...