Depends on what you mean, by bottleneck. Are you referring to gaming performance? I assume you are.
Also it is important which games you play, at what resolution etc.
Give us some more info so we can help you.
Why do you think you have a bottleneck? What are you running that isn't flowing smoothly? What settings?
Quake 4 benefits from from a Dual Core CPU (one of the only games)
Oblivion is bottlenecked by nearly any graphics card.
I really can't help you much unless I know more...
But to answer your question
Is P-4 3Ghz a bottleneck 4 7900GS?
In some situations, yes. In others, no.
Gaming at lower resolutions, with lower AA+AF settings, you might be missing out on high frame rates because of your CPU, you would be getting medium FPS. For example, in Doom 3 you would probably be getting around 85 FPS with that CPU. If that is enough for you, good. If it isn't, a better CPU will get you higher scores.
Well I didn't really notice any bottlenecks or speed straints.....I actually don't play much games........but I got all my hard drives filled with games ^_^ (that is 750GB btw)
I really like to install a game, fire it up and know the feeling I could max out the graphics and watch how pretty it is....then shut it down and never to touch it again. I don't play at extreme resolutions, mostly 1280x1024. Some at 1600x1200 with all settings maxed out and AA AF on max too. The only game tends to hack a bit is Oblivion at 1600 But the rest seems to run pretty smoothly.
The reason I'm posting is I want to upgrade again, don't know if I should look at upgrading the GPU or the CPU/Mobo or just the CPU alone. I wanna go for AMD, so was wondering if its worth the upgrade or should I hang on a little longer?
If I was getting a new build right now, I might get a C2D system. However AMD's quad core is coming out in 2H of this year. How will it perform? Nobody knows. But we can all assume it will be significantly better than today's Athlons.
It might be a good idea to hang on until then. See what Intel and AMD have on the table at that time, and make a decision.
Oblivion is a monster that will make 99% of systems stutter. If you want smooth Oblivion, think about a GeForce 8xxx series card. (Only 2 released so far) But with those cards, you really would want a new system to run them in.
However if you want to upgrade now, I would get a new CPU/mobo with a cheap C2D and overclock the hell out of it. Wait until later for a GPU upgrade, especially if you don't play games often.