Greetings:

Is there a formula for Determining optimum RAM speed for a given CPU? I'm wanting to build a new system from scratch, starting with the best price-to-performane cpu in my budget, and then choose a motherboard and RAM to go with it. But choosing the mobo and RAM requires knowing what kind of RAM I will need. I don't want to overspend on RAM that's so fast that it's increased speed does me no good, but also don't want a slower speed to be the bottleneck in my system.

Thanks for your help.

Hi,
Two places to look would be:
TigerDirect.com - Computers, Computer Parts, Computer Components, Netbooks & Electronics
TVs, Computers, Cameras, GPS, Home Audio, Desktops, Laptops, Consumer Electronics, and More at CircuitCity.com
With the second being the site bought by Systemax from the bankrupt retailer. I personally find the first to have the most selection.
Most MBs offer the flexibility to run multiple speeds on the bus nowadays.
Peace,
Clarke

No, there is normally only two choices: that which is compatible with the selected bus speed for the CPU used, and that which can be clocked faster than what is required for the selected bus speed. Unless you are planning to overclock the system, there is no advantage to using modules capable of faster clock speeds than the minimum required.

I'd suggest you first pick a motherboard with the features you want and then purchase a CPU and memory to fit the motherboard. The motherboard's technical documentation will state what type of memory is best used with which CPUs. The motherboard vendor may also formally test and recommend specific memory module brands and models for compatibility. Otherwise, I've always had reliable results using Kingston modules.

I always use newegg.com. Good prices... great experience every time. I love the site because it details the things you need to know for each product.

Scleros gave good advice.
Just make sure you get DDr3 and with the highest speed supported on your motherboard and the lowest CAS latency(depends on only your budget).
If you don't use a 64bit OS you can't access anything over 4gigs.
Also if you go with an i7 you can/should get triple channel ram. (I recommend 3X2gig sticks... )
if you go with AMD you can only get dual channel.
(2-4X2gig sticks... )

Definitely start each build with a solid Motherboard.

I just built a system for about 1500 with i7 6dids ram gtx275 graphics card and watercooling. Spend more money then you think on the Power supply. I recommend a >80 efficient one. It will save on your power bill but cost me $200. This will be good for the next build some 5 years down the road.