Optimizing my RAM with my CPU

[Daethar]

Decided to resume building a PC since hardware is now incredibly cheap for mid/high end.

I was reading about different types of RAM, and one source said that DDR3 is highly unnecessary, because the CPU's and mobo's can barely match DDR2-800's full potential.

There was also a formula saying, since the FSB is quad pumped and the DDR RAM doubled, the optimal ratio is 1:1 meaning FSB/2 = RAM speed.

That site was a little older, but it's numbers made sense. I wonder if they are including Core Duos and Quad Core CPU's, though.

So my questions are*:

1) What is the correct exchange for a Dual Core cpu and memory. Is it still FSB speed/2 = max memory speed? Or do Dual Cores have a different multiplier, and thus ability to use higher clocked RAM?
2) What about Quad Core?
3) Considering #2, would a Quad Core CPU of say 2.6gHz be better than a Dual Core CPU of 3.2gHz using RAM that does not operate at the maximum the FSB allows?
4) Would I be better off with lower voltage RAM and tweak later, or buy higher voltage that I know operates with stability at those increased timings?
5) Why would I want DDR3 over DDR2?
6) How much performance am I getting with a DDR2 RAM upgrade, i.e. DDR2-1066/1600 over DDR2-800?

*ignoring factors such as "it will be better in the future," because PRICE and TIME are the main factors now. I want the PC soon, and I will go for upgrades later when they become necessary, or at least affordable.

[UGHQ_Juason]

1) What is the correct exchange for a Dual Core cpu and memory. Is it still FSB speed/2 = max memory speed? Or do Dual Cores have a different multiplier, and thus ability to use higher clocked RAM?

No difference between dual and quad core really. Ideally you'd want the bus speed synched at some whole number ratio. My testing on a Quad Core Extreme 3Ghz system @1600mhz FSB shows only 1-2% variation between being synched and not synched, however. So with a FSB of 1600, I think you'd want to get some DDR-6400 (800Mhz) RAM. If your FSB is 1333 you could settle for DDR-5400 (667Mhz).


3) Considering #2, would a Quad Core CPU of say 2.6gHz be better than a Dual Core CPU of 3.2gHz using RAM that does not operate at the maximum the FSB allows?

Quad core is only better if your application is taking advantage of it. A 3.2Ghz Dual Core will kick a 2.6 Quad Core's ass any day of the week outside of a select few games. Quad Core also has a lower max die temp and overclocks poorer.


4) Would I be better off with lower voltage RAM and tweak later, or buy higher voltage that I know operates with stability at those increased timings?

I always buy OCZ and have never had a problem. DDR2 can go up to INSANE speeds anyways (PC2-9600 (1200mhz), so you shouldn't need to play with voltages outside of liquid nitrogen cooling.


5) Why would I want DDR3 over DDR2?

Future proofing? The benchmarks and writeups I've seen with DDR3 show its latency is poor. So you effectively need ~33% more speed on the ram to match DDR2 performance. It is also more expensive.


6) How much performance am I getting with a DDR2 RAM upgrade, i.e. DDR2-1066/1600 over DDR2-800?

5-8% is my estimate. Of course this depends on the application, your processor and motherboard and the RAM timings. RAM timings being a big portion of it all..


Out of curiosity, what are you looking to get out of your system? Keep in mind the video card counts for the lion's share of your score.

[Daethar]

I am looking to be able to play the "next generation" of games. My current laptop has been lagging around minimum requirements for PC games lately, but I was okay with low settings over upgrading. Dawn of War 2 has finally set the bar higher than what it can handle, and so now seems like a great time to get an upgrade.

For "future-proofing", I am hoping for about 2 years before needing to upgrade again. In this case, bleeding or even cutting edge is not an option. I'm aiming for what still kicks the ass of games out there, but may not give me all the bells and whistles, like physics cards or 3D goggles or crap like that. My "spending money" is a little tight right now, so I want to stretch it as much as possible. However, prices have been great recently, and so I've got 4gb of RAM lined up to purchase, hard drive picked out, GeForce 8800 GTX 512mb overclocked already bought, and am just trying to get everything aligned before I decide on the right CPU, Mobo, and Power Supply.

For what it's worth, I had been thinking about a wolfdale 3.16(?)gHz Core Duo, but a couple of quad cores are similar in price right now. If I can get future proofing for the same price or at most $20 difference, I am totally for that.

[UGHQ_Juason]

GeForce 8800 GTX 512mb overclocked already bought

That's too bad. The 8800s are more expensive then the 9800s from the price comparisons I've done, and are too slow for your machine to be a true "next gen" performer.

Physics cards - don't. Nvidia bought and put PhysX support into their video cards. You just check a box and get it for free, provided your GPU isn't too heavily taxed already by the graphics.