I’m trying to build/purchase a new PC and it’s been a long time since I looked into parts.
Unfortunately, I know almost nothing about processors, specifically the differences between single, dual, and quad core processors.

I’ve heard that most programs only use one of the cores in a multi-core CPU unless the program is specifically designed to take advantage of the multiple cores. So, if I have a dual or quad core, I may only be getting the processing power out of a single core, and thus would be better off with a strong single core since the mutli-core CPU’s I’ve seen individual core speeds seems to be slower.

Example:
Single Core (3.3 GHz)
Quad Core (2.2 GHz on 4 cores)
Thus, the single core is faster if only one core is being used?

I’ve also heard multi-core CPU’s can cause instability/errors/weirdness in some older programs/games. If I get a dual/quad core processor, will I encounter this kind of problem, or is it just an unfounded rumor?

I’m not experienced enough to do any modding yet, so please keep any recommendations limited to base settings on the hardware. (No over clocking.)

Your basic ideas here are correct.

If you are only going to run "old" software then a single core or hyper threaded might be slightly faster.

There are many other factors such as the FSB of the CPU and of the motherboard.

There is probably not much sense in putting a quad core on an old motherboard. Most will not support it to begin with. New boards have faster FSB to match the quad cores which will then run faster even with a slower GHz reading.

Most motherboards currently on the market are "Quad Core" ready. But I'd say this is only true within the past year. Also for best results you want a PSU that is "Quad Core" ready as they have a dedicated 8 pin 12V.

Thanks for the help, jephree.

I'm now thinking about getting either a Core 2 Duo E6850 or a Core 2 Quad Q6600, and I was wondering: is there any reason why a dual core would be better then a quad?

I was hoping I could just drop the new CPU onto my old motherboard, but it doesn’t support it. Is there any brand or specific board you’d recommend for dual or quad core CPUs?

Also, does a PSU with dedicated 8 pin 12V have a second wire that I connect to the motherboard? Or does it just produce more power?

I like Newegg's site because of their filtered search options so that is why I link to them.

You have mentioned no budget so I am going high end to begin with. In general:

I have been using this board for the past several months:

http://www.newegg.com/Product/Produc...82E16813188013

Very nice board.

You will find these boards have 8 pin ATX 12V slots rather than the old 4 pin.

High end PSU's offer this 8 pin connection specifically for Core 2 Extreme CPU's.

Here is the PSU I use:

http://www.enermaxusa.com/catalog/pr...2c7105b15fcc57

Thanks for the suggestions.

I think I may buy a of Galaxy DXX EGX1000EWL 1000W Power Supply. It seems to do the job, and then some!

Another consideration here is the case in regards to the PSU physical size.

With that Galaxy you are going to want a "Full Tower" case.

Also if you go for high end Graphic cards such as 8800's you will need a "Full Tower" to accommodate their extra length and depth.