I'm building a new PC this month, and I've noticed that right now I can get an i5 750 @ 2.66GHz or an i5 650 @ 3.2GHz for the same price. I understand that the 750 is a true quad-core while the 650 is a dual-core w/ hyperthreading, and going true quad is generally a better idea. But is the extra speed of the 650 going to make up for that? I do a lot of work in After Effects, so multiprocessing matters to me. I'm just not sure which of the two will give me a better raw speed across all the cores, fake or not.
Does that mean that, for example, if I'm rendering on four cores, 4 cores @ 2.66GHz on the 750 will render faster than 4 "cores" @ 3.2GHz on the 650? Or is it really only worth it if I'm overclocking the 750? I don't plan on overclocking -- I'll be doing a lot of work on the computer, and I can't really afford to mess with its stability.
It depends what you're going to be using the computer for. The chips score nearly equal scores in SYSMark 2007 (edge to the i5750) but then i5 750 beats out the i5 650, often handily, in most other tests. Only when limited to a single threaded application does the i5 650 gain the upper hand. Unless you have a very specific application that is limited to 1 thread and that you will be running all the time, between the two I'd go i5 750.
You may find this to be helpful: http://www.anandtech.com/show/2972/the-rest-of-clarkdal...
It answers your question about rendering, showing the i5 650 to be faster only when limited to a single thread. So if you're rendering with a program that utilitzes multiple threads, then the 4 real cores of the i5 750 win out.