Originally posted by: SonicIce
What games so far take advantage of it?
Like some others said, there's a difference between supporting multiple cores vs. being optimized for multiple cores. Most games today (released in the last year or so) support multiple cores by simply splitting CPU load amongst your cores. Scaling is pretty linear and would match the same CPU utilization with less cores (ie 2 cores @ 25% = 1 core @ 50% or 4 cores @20% = 1 core @ 80%). This is different from being optimized for multiple cores where multiple threads are specifically coded to take advantage of additional cores (1 core @ 80% vs. 4 cores @ 40%).
What I've noticed however is multiple cores can have a big impact if any core is pegged at 100%. This is obvious enough with a single core, as that core is being pushed to the limit. Being able to offload any additional processing to a second core results in a nice performance boost. This can range from being completely choppy/unplayable to reducing/eliminating slowdowns or increasing FPS. There's also a similar, yet less noticeable benefit if one core is pegged at 100% on a dual core system. In many games, if one core may be pegged at 100% and the other is say 60%, you can balance that load out by alt-tabbing, going to Task Manager and finding the game process. Choose Set Affinity and all cores should be selected. Just confirm or check uncheck a core, then go back into the game. You should see load balance between the cores so instead of 100/60, you'll see 80/80. Seems to cut down on slowdowns for me. This seems more like a Windows CPU management issue rather than a game issue, and probably occurs for games that aren't specifically programmed to take advantage of multiple CPUs.
The other area I've seen a nice boost with multiple cores is if you're running other programs/games/software. FRAPs in Vista is extremely CPU intensive when recording to the point it would often peg my C2D (80-100% on a single core @ 3.1GHz). This would result in both cores being pegged at 100% in some games (Witcher, Crysis, WiC etc) and make the game nearly unplayable. The most recent FRAPs patch cuts down on CPU use a lot while recording, but its still pretty significant. Moving to a Quad Core and spreading that load across 1-4 cores improved performance significantly for me while recording in FRAPs. Other benefits would be running multiple game instances simultaneously, which is great for MMOs or even something like Diablo 2 (Power Leveling or self-muling etc). Similarly, running multiple games, like an MMO or RPG with an FPS or RTS where you don't want to log out in one but just want a change of pace. And of course there's those who want to do other things with their PCs while gaming like encode/decode/download/dist computing etc.
Overall I'd say there's not much advantage to 4 cores if you're only running a single game, but there definitely is with running a dual core vs. single core. There's very few single apps/games that push my Quad over 50% (PowerDVD while decoding VC-1/MPEG4 can at times), which is very close to 100% on a same-clocked Dual core. There are games I've played that would've pegged a single core easily before getting to any background processes eating up CPU cycles. If given the choice (stock or OC'd) you're probably still better off going with a faster clocked Dual Core than a slower Quad Core if everything else is the same (FSB, L2 cache, memory speed/timings, GPU clocks etc). If you like to multi-task, record with FRAPs, or run multiple games/instances simultaneously, then more cores certainly won't be wasted.