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How to determine which component will cause a bottleneck? Answered

I have a system with a Pentium 4 at 2.4 Ghz, and I'm assuming that the P4 would be the component to cause a bottleneck.  I've maxed out the RAM at 2 GiB (it's DDR 533 Mhz I believe). Anyways, I'm trying to get it to do some (moderate) 3D gaming.  So I'm wondering, if I were to buy an AGP ATI graphics card, would a card with only 120 stream processors result in a bottleneck with the GPU instead of the CPU?  Or is the difference between 120 and 320 stream processors negligible (assuming clock speeds and VRAM are equal)?  I'm not expecting to run Crysis on this rig, but I'd like it to be able to handle most modern games on low settings at least.  Any input is appreciated.


I have a second power supply available.  A 400 watt one lying around, and a 200 watt that came with the computer in question.  As for powering the GPU separately from the motherboard, I can, since the graphics cards in question need to be plugged directly into the power supply.  I just need to get both power supplies to turn on/off at the same time.

Well, after doing some research, it would seem that the general consensus is that the Radeon HD 3850 is the best graphics card for the AGP bus, and that it would eliminate any possibility of a GPU bottleneck.  It would also seem that an equal balance of bottleneckage would be provided by this particular Radeon HD 3650.  I'd rather go with the more expensive card and not be wondering if there is still better performance to be had, so I'll probably get the 3850.

However, the PSU in the machine in question is a 400 watt wimp with only 18 amps on the 12 volt rails.  The recommended PSU for the 3850 is 450 watts and 30 amps.  I've had a idea to power the main computer with it's original 200 watt PSU, and use the 400 watt to solely power the GPU.  Hopefully then it'd be able to get enough juice and not BSOD on me.

So I'm guessing this Radeon 4650 would be total overkill?  A Radeon 3650 was my second choice, perhaps that would be sufficient?  The only nVidia card that seems to be comparable is this 7600GS.  I prefer nVidia but I'm not sure how that particular card compares to the ATI ones I'm looking at.

I got the system for free, so I'm not too keen on spending any more on it than I have to.  The memory is as fast as it gets, sadly.  The computer itself runs pretty fast (I've got Vista Ultimate 32-bit installed; yes, I know, not the most optimized OS out there), it's a bit speedier to boot up, log on, etc., than my main rig w/ a 3 Ghz Dual Core and 2 Gigs of 800 Mhz RAM.  I've also got more startup programs on my main rig though.

The BIOS don't support overclocking, but I seem to recall seeing someone manually overclock their CPU by physically changing the voltages... is this even possible, or is it a recipe for a nice new paperweight?  Anyways, you've given me enough evidence that I think I'll go with a more decent graphics card.  Thanks for the input.

What GPU does it have at the moment?


Onboard video, no 3D acceleration whatsoever.

Fitting a card is definitely going to improve things then. Games will tend to use a GPU where they can.


Depends on the specific application, I think -- how much of the computation is offloaded to the graphic card vs. occurring in the general-purpose CPU, how intensive the graphics are vs. how complicated the game logic is, what resolution you're trying to run at, how jerky you're willing to have the motion become...

I think I'd check the suggested-minimum-requirements on the game packaging and see what the publisher recommends.

But I've so far avoided games that need ungodly amounts of graphics support, so my idea of what's acceptable minimum may not match yours.

Pretty much all of the games that I'm intending to play require a 2.4 Ghz single core or higher... which makes me a little nervous.  In the past, I've been able to ignore the minimum requirements and get away with it, but I'm a little hesitant about doing that now that I'm actually spending money on components.  I'd be ok with modern titles running at around 20 FPS with all of the settings turned down... whether or not that actually happens in the true question here.  Newegg does have a good return policy :).