What should I look for in a processor?

Question

What are the facts I need to consider before buying a new processor ? As there are [for example] 3.2 GhZ Intel I3 / Core 2 Duo / P4 / equivalent AMD.

I'll buy a new processor and my budget is around 145 $
I'll use the processor for playing old games [released before 2011 :D], programming using Visual Studio 2010, doing basic image editing on Photoshop Creative Suite, running Windows 7. I'll buy 8 GB RAM [4*2] along with it [outside 145 $].

Answer 1

You will probably answer this purely from the price point, but here are the things to consider in general:

Cores:

Things are getting better, but parallelism in home computing is pretty poor. So, during your regular usage, if you are only ever running a couple of processes, then anything more than 2 cores will likely be wasted, and certainly anything over 4 will generally go unused. However, one of the exceptions to this is games, as usual they are at the forefront of PC tech, so you will benefit on the gaming side, but only up to a point (graphics card will be far more important).

If you plan on running Virtual Machines for testing or similar then having more cores is always nice, but not essential unless you are pushing for performance per VM.

Clock Speed:

Not as big a deal these days as it used to be - you generally don't have to pay much attention here, and the main thing to look for is the "sweet spot". You will usually see fairly linear relationship between price and clock speed up until you reach a sharp increase.

Socket/Technology:

The latest socket/technology will usually cost a little more but buy you time in terms of future proofing and upgradeability. IMO it's worth getting the latest socket over a 10% difference in clock speed as a result

Motherboards:

Motherboards are the other thing you are going to have to choose directly related to CPU and will impact your spending significantly. Again, you will generally pay a premium for the latest tech and again I generally would take a lower spec board if it got me the latest socket or tech - why? because you will then be able to upgrade further into the future (think a new graphics card in 2 years to get you over the hump, or the ability to get up to 16/32GB of RAM from 8 cheaply in a similar time frame).

TL;DR version: go to NewEgg, even if you don't intend to buy from there and sort the CPU's and motherboards by best rating - check out what won the customer choice awards and read some feedback. Most of the time that will make up your mind more quickly than anything I mentioned above :)