so i was wondering which was faster:

quad core with 2ghz

or

duo core with 3 ghz

i don't really get how the number of processors relates to the clock speed, hopefully someone here knows

We Chinese eat rice...ricers that is.

The Quad Core is faster, as if I recall correctly each core is 2ghz.

Buy a i7

スズキスイフト

Get dual-core, seriously. Close to no programs use more than one, not to mention two CPU's at a time. Only get a quad-core if you do some serious multi-tasking.
If you only want it for general use and gaming, a dual-core 3ghz will beat a quad-core 2ghz because 99% of the games out there use a MAXIMUM of two cpu's.

Yes all cores are syncroniously clocked, they all use the same multiplier and bus to make the final frenquency. So when it says it's a 2GHz, all cores operate at that speed

With that said, the Dual cores will be the wisest choice right now, with single user SMP being really barely optimised to even make use of 1 core, let alone 4 or in the Core i7's case, 4 cores where each can process 2 threads ...

If it's a gaming rig, the best results are still getting the highest possible clock on the CPU while getting the mem bus up as high aswell for higher bandwidth. And Quad cores just dont overclock as well as the Dual core once.
My suggestion, as a minimum, get a C2D E8400. These beasts will (regardless of stepping) run over 4GHz 24/7, memory bandwidth will hover well around 8-10GB/s.

There's just no need for quad cores before we get better OS'es

What about the very cheap Intel® Pentium® Dual-Core E5200 Boxed, FC-LGA4, "Wolfdale-2M"? That one could be easilly pushed to 4GHZ

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Yes, but you'll have to make do with a 2MB L2 cache instead of the 6MB, which was one of the biggest advantages of the Core2 architechture.
Id still go for a E8400, it's got the full 6MB L2 cache of all "real" Wolfdale's. Not just being a speed and cache binned part like the E2x00 and E5x00.