I'm having a bit of a problem here, and I'll explain you why:
I have a high end PC, and I can run nearly every game, (expect crysis max everything), fluently. By this I mean 30-60 fps.
Also, I've been playing CS:S for 4 years, ad heaven ever had problems with this game on any pc... I recently installed CS:S and ever since, I've been getting CPU DRAINAGE! 100% for a sinmple and low-detailed game as CS:S. This confused me, since i can runj every game with about a 70% CPU usage.
I reinstalled CS:S, and no improvement ever since.... 100% CPU!!! 100!
Also, this is not due to my ping, I checked that... (I'm getting performance issues in game btw)
My PC: (sorry for the xtra info..)
Processor: AMD Phenom(tm) II X2 550 Processor (2 CPUs), ~3.1GHz
Memory: 4096MB RAM
Hard Drive: 750 GB
Video Card: ATI Radeon HD 5700 Series
Monitor: IIyama 22" LCD
Sound Card: Speakers (High Definition Audio Device)
Speakers/Headphones: Logitech X- Series
Keyboard: Razer Lycosa Mirror Edition
Mouse: Razer Diamondback 3G
Mouse Surface: Razer Sphex
Operating System: Windows 7 Ultimate 64-bit
Motherboard: MSI 770-G45 - UDMA133, SATA-300 (RAID)
Computer Case: Coolermaster Centurion
It'll now use up to 2 cores now, before it wouldn't use more then 1 core. You might see as much as a 10% increase in fps in some areas, but for the most part its just wasting cpu as far as i've been able to see. It's also laggy as all get out...I was so used to running 100 tk servers, but now 66 tk doesn't even run right...It lags so much, it feels like a 33 tk server wherever i go. I don't know what all exactly they've done, short of disabling -tickrate for servers, and adding all the misc crap (achievements etc)...But they've pretty well hosed the game for me.
So...yea it's not just you having it max out your cpu. I'm running a quad and it sits at 50% as soon as i load it up.
Team Fortress 2 and Counter-Strike: Source are now on the same engine, (The orange box engine) the update improved performance for Counter-Strike: Source by allowing two cores to be used at once. Valve did something similar with DoD:S a while back, increasing performance for a lot of people but making the games unplayable for just as many people.
As an example,
90+ FPS before the CSS Orange Box update
130+ FPS after.
Keep in mind maxing the processor is a good thing, this means the game is now utilizing all of your resources which is a good thing. Want the game to use less resources?, buy a better CPU.
Meh i'm not certain maxing the cpu is where we really want to go...All that means is that when something like...say your antivirus or some other system resource goes to do something, it takes directly away from resources dedicated to the game, rather then indirectly. And 10% to the 90 fps is 99 fps =P, /grumble. ;-)