I'm somewhat unclear about dual core processors. If both of the processors are 1.4 GHz, does that mean my computer will qualify for 2.8 GHz requirements? In other words, do the GHz of both the processors add to each other, resulting in your computer's overall GHz? A game that I want to play requires 3.0 GHz to play, and I was wondering if I would need a computer with two 3 GHz processors, or just two 1.5 GHz processors. Thanks for any help.

yes and no, the comparative cpu power you get is probably somewhere between 1.5 and 3.0 but this will depend on how well multi-threaded the game you want to play is

I think there are four big problems with your understanding (probably pushed by greedy hardware vendors, performance-tweaking framerate obsessives and Best Buy employees).

1. Clock speed doesn't mean jack. There are so many other factors that affect the performance of a CPU than the number of cycles it can do a second -- CPUs like the PowerPC do more heft per cycle, so they can get better performance at a lower clock speed for some tasks. That's part of the reason the Core Duo chips generally have a lower clockspeed than the equivalent P4 (the other part being that the P4 architecture was nearly completely designed for the marketing tool of getting the highest clockspeed possible). If raising the clockspeed were a magic "go faster machine" we'd just slap a couple 5.4GHz oscillators on there and try to get it to be stable.
2. SMP doesn't mean "double the performance". Both CPUs won't be saturated, and even if there were, there's synchronization and access issues that add a significant amount of overhead. Most games now are single-threaded anyway, so you will see zip improvement from adding an extra CPU. As developers wrestle with multithreading, it'll get better, but at the moment you're unlikely to wring much benefit from it for playing games. We've had multiple CPUs in computers for almost twenty years now; if they were a guaranteed double-speed benefit you'd certainly have seen them in consumer hardware before we started rubbing up against Moore's Law and we'd have fixed a lot of this multithreaded-game-engine crap a long time ago.
3. Run the game's demo before you waste the money on it. If you're not sure it's going to run fine on your hardware, try it out before you buy the game.
4. Game requirements are usually made up. I pull them out of my ass, personally. I've had varied experiences with "minimum" requirements being way better than the real minimum, and experiences where "recommended" hardware produced abysmal performance.

My guess is dual 3.0 processors.
To answer your other question, no two 1.5 processors don't add up to one 3.0 processor. Though the math would make it seem that way.

One more thing - most games out there right now rate their cpu speed requirements as pentium 4s. That is, a pentium 4 at 3GHz. Now, pentium 4s do not do as much each cycle as Athlon64s or Core2s. And thus, for example, an Athlon64 at 2GHz will most likely be FASTER than a 3GHz pentium 4.

Multi-core CPUs are like a couple of single-core CPUs slapped together (well, sort of, not exactly, but it's easy to visualize it that way). They can do more work faster, but a single piece of work as fast as a single-core CPU. This "work" is a thread. If the game is multi-threaded, each core of the CPU will take some threads for itself, and leave other threads for other cores. This will be faster than if your CPU has only one core, and that one core did all of the threads. On the other hand, if the game used only ONE thread, then multi-core CPUs wouldn't really do much as only one core will be used - the same thing as if you're using a single-core CPU.

Also, see if the game in question is in the System Requirements Lab. If it is, you can do an online check of your computer and it'll supposedly tell you if you pass minimum or recommended requirements, and it can tell you what fields your PC is lacking in.

I have personally had great experience with the dual core prosessors, both AMDs and Intels. There are in particular two main advantages in my opinion:

1. The extra core adds more speed. This is very noticable when you're doing number crunching algorithms and such. The performance have been very close to doubled in parallelizible algorithms with little communication. On games and such I haven't done any experiments though.

2. When one program messes up you can still work with the computer. Quite often I get problems with one prosess maximising it's CPU use, often MSN messanger, explorer or Opera. When this happens on a dual core you will usually be able to work unaffected with the other core. This is of course also important when you have an important program running in the background.

I believe at this point, any core 2 duo cpu will out preform the fasted P4, even the so called Extreme Edition. A Core 2 Duo E6300 is fast enough to play any game out there.

Quote: Original post by tstrimp
I believe at this point, any core 2 duo cpu will out preform the fasted P4, even the so called Extreme Edition. A Core 2 Duo E6300 is fast enough to play any game out there.

Not exactly, the fastest P4 was run at 8001MHz (linky), and according to what I've read it was faster than a Core2 Extreme.

A P4/PD Extreme should be faster than a stock E6300.

The only game I know of that requires 3.0Ghz of processing power is Supreme Commander. What I think the issue with that game is (as far as whether you really need the 3.0Ghz) is its mostly the AI that requires that. I have been in 3v3 online games(thats 3v3 human players) and also been on 3v3 computer players. The game runs much slower against computer players. I think the limit on my 2.0Ghz Athlon 64 X2 is 3 computer players before it get unplayable.

Quote: Original post by agi_shi

Quote: Original post by tstrimp
I believe at this point, any core 2 duo cpu will out preform the fasted P4, even the so called Extreme Edition. A Core 2 Duo E6300 is fast enough to play any game out there.

Not exactly, the fastest P4 was run at 8001MHz (linky), and according to what I've read it was faster than a Core2 Extreme.

A P4/PD Extreme should be faster than a stock E6300.

Too bad it requires liquid nitrogen cooling for that...