RAM speed on eVGA 750i

So was just looking around at prices for my new build I'm getting next month, and was looking at scan.co.uk and it said for memory, the only speeds it supported was 800 and 1066. I went to look on the eVGA website, and it said all DDR2 RAM was support, so I thought fair enough.

The RAM I'm using right now is Corsair XMS2 667. My question being, is 667 RAM in dual channel going to put up alright on the 750i motherboard?
From reading other forums, it says that 667 DDR2 in dual channel has the same bandwidth as 1333 in single channel, so saying this I'd say it would be okay? I know 800 would be better for me, but I won't be doing that upgrade for another few months yet, as I'd have thought the RAM I have now is enough.

Edit - Another question: I've never used Intel CPUs before, but how much effort would it take to get the RAM from 667 to 800 when overclocking the CPU?

RAM speed and memory bandwidth are two different things. DDR2 667 describes its speed: 667MHz DDR. It's bandwidth is 5.4GB/s. They use the memory's bandwidth as a second name, which in your case is PC-5400. You can use the names interchangeably.

However, DDR2 667, aka PC-5400 does not have the same bandwidth as DDR3 1333, aka PC-10660, which has a speed of 1333MHz DDR and a bandwidth of 10.6GB/s. No amount of overclocking is going to get DDR2 667 anywhere near the bandwidth of DDR3 1333 or DDR2 1066. Even getting close to DDR2 800 would be a phenomenal feat.

Having said all that, memory bandwidth doesn't mean squat anymore. Sure, ideally you'd like to be running at least 800MHz RAM, but after that, from 800MHz to 1100MHz DDR2, the gains aren't dramatic... they're there, they're just not dramatic enough to make a meaningful difference.

As for your board specifically, I don't know if you're going to have a problem as you RAM's speed isn't even supported? In theory it should work just fine; in practice, I'm not sure? It might work, but with RAM so cheap, you may as well bite the bullet and get at least DDR2 800?

What I said about the bandwidth was 667MHz in dual channel has the same bandwidth as 1333 in single channel. So 5.4GB/s on 667MHz single channel, would effectively double to 10.8GB/s, which is around the same as 1333MHz in single channel. It won't operate at that speed, just up to that speed. That was what some people were talking about on some hardware forum.

The RAM I have is supported as well according to the eVGA website. Though if the theory that I've read of 667MHz in dual channel is right, then I suppose I won't have a bottleneck problem with the RAM.

I think those discussions are more academic? 2x667 would equal 1333 if you only ran one stick of 1333? Who does that?

Dual channel, if memory serves me correctly (it may be hazy on this) refers to the interface between cpu and memory. Single channel is half the size of dual... it doesn't specifically have to do with the RAM in question.

you'd probably be fine to run it. but you might as well spend $50 bucks and get some good Crucial DDR2-800 ram somewhere.. that would be a good improvement.

If this 667Mhz runs fine, then I'll probably leave the RAM upgrade until around Christmas.

My main concern though was running in to bottleneck problems with it.


So to what Fumz said, overclocking the speed of the RAM doesn't mean you're overclocking the bandwidth of the RAM itself?

As you increase RAM speed you also increase it's bandwidth. I was just saying that in order to increase DDR2 667's bandwidth to the bandwidth of DDR2 1066 you'd have to increase the frequency from 333MHz to 533MHz, and that matching DDR3 1333's bandwidth would require an increase to 666MHz, and that would be difficult to do.

Well yea I understand that, as my original point was 667 RAM in dual channel is the same as 1333 RAM in single channel, even though nobody runs a single 1333MHz stick, but my theory was that if a 1333MHz stick in single channel would run fine, then I'd imagine 667 RAM in dual channel would be fine as well.

But thanks for the help anyway

Yeah no, don't get me wrong, I think it'll run fine too. I guess I was just confused by the wording of the initial post?

Yea, you might have just missed the dual/single channel theory bit, but no worries

Yeah, the last time I bothered looking into dual vs single channel we were running AMD XP cpu's... and it didn't really matter whether you got an nforce with dual channel or a VIA chipset with single channel; they both performed about the same. What I was missing was that "single stick" part as I assumed everyone was talking about using 2 sticks.

Not really sure about 2 sticks of 1333 in single channel vs 667 in dual, but it would be interesting to find out?