How much of a difference, for gaming, does using PC2-6400 RAM instead of PC2-5300 make in a Core 2 Duo system (like, say, an E6550)? Have any benchmarks been done on the subject?

Thanks!

I haven't seen any benchies, holding all other variables constant, but swapping memory kits.

I think it does matter. I made a post in the overclocking section that showed a NOTICABLE difference when the ram speed is slower (2-7%). Yet, ram speed seems to underdiscussed.

Not sure what you're budget is, but the 6400 ram is VERY cheap right now. I'd recommend going that route in a heartbeat.

See other posts about RAM ratios & timings. My opinion is that if you are building a new system (NOT for overclocking) then get the fastest FSB that you can and run your memory at 1:1. In your case an FSB of 1333MHz would then require 675MHz memory. Of course some people prefer to buy higher speed memory now in case they want to run a faster FSB later (due to a new processor) but on most boards that will require overclocking as there aren't many boards out that officially support FSB1600 under normal operation.

Yeah, if the price is really close, I'll go with PC2-6400, but if it's not... PC2-6400 is faster than PC2-5300, but how much faster? It surprises me that no one's investigated.

Memory offers the least amount of performance increase when compared to modifying bus speeds and CPU multipliers. It is not unusual to relax the timings to 5-5-5-whatever and go 1:1 when overclocking, then once a stable FSB and multiplier is found, come back and tighten them up and/or change the ratio.

However, there are gains to be made, depending on your system. From what I've read, that 2-7% is as good as any when estimating an increase between the two modules your considering.

As you're looking at the impact on games, and if that translates to a direct increase in fps, then a 30fps game will go 30.6 to 32.1 fps, using the above persentages.

The 667 is still the best value DDRII RAM avaiable, so don't go with 533 if you can. You have not indicated the FSB speeds you're working with, but the E6550 is 1333FSB, so run the 667 at 1:1 on a 1333 board, or just set it to auto.

If you're going to OC anytime soon and your board is 1333 already with head room to spare, have a hard look at 800MHz modules, if your budget allows.

Although it compares PC-5300 to PC-6400, with a bit of scaling with respect to FSB speeds, this may be helpful:
http://www.legionhardware.com/document.php?id=628
and
http://www.legionhardware.com/document.php?id=630

So the moral of that story seems to be "buy low CAS latency memory" ...if I'm following that right.

I have no idea what that means. (Okay, I have a slight idea, but not much of one.)

Here's how I use memory: I carefully put it in the motherboard, I leave it alone. No overclocking, no nothing.

Would putting it in the mobo and leaving it alone do that?

I have no intention of ever overclocking. I should have mentioned that. D'oh.

FWIW, here are the parts for the system that I might make as soon as I can afford it:
https://secure.newegg.com/NewVersio [...] 2DuoSystem

"Would putting it in the mobo and leaving it alone do that? "
Yes, whatever your FSB is (1066/1333), if you use 667 RAM and leave the BIOS set for auto, you'll be good either way. If you've not changed this, it will be on auto.

When you use this CPU and board combination, it will run at 1333 anyway. With the 800MHz RAM and the BIOS is set for auto, it will use the appropriate ratio, no user intervention needed.

The price of the 800MHz appears ok (after rebate) compared to other 1GB 667 sticks around $20.00-$30.00 range.

"Here's how I use memory: I carefully put it in the motherboard, I leave it alone. No overclocking, no nothing. "
Works for me.

"I have no intention of ever overclocking. I should have mentioned that. D'oh."
Good you mentioned. I've previously toyed with the idea that when someone doesn't mention over clocking, that they're not over clocking, but I was shot down in flames for that. Live and learn