CPU bottleneck Video Card

[Ruroni]

Hi, I have a question regarding CPUs and their effects on video cards. I would like for someone to help me understand how does a CPU bottleneck a video card. And more to the point, at what speeds does a certain CPU become the bottleneck for any given card.

For example, say someone has a Radeon 9800pro, at which speed? would a CPU not be a bottleneck for it? For that matter, I guess if you can explain the inverse, I'd be interested in reading that as well. If you could make some reference as to where your knowledge comes from, that would be much appreciated.

Also the effects of RAM would be nice too understand too.

Thanks.

 

[bjc112]

Well it depends on the card, as some scale better than others...

I do know that even with a P4 @ 2.53ghz there is some limiting being done..



All the more reason to overclock.

 

[modedepe]

Ok, here's how a cpu could be a bottleneck. For instance, say you're trying to play a game that requires a 1.5ghz p4 and a radeon 7500 bare minimum to play it. Now, you could upgrade your video card to say a radeon 9800 pro, and you would get some increase in performance. But, because the cpu is the bare minimum it will obviously be the limiting factor. And of course, this works the other way around. You could have a 7500 with a p4 3.2ghz, and the 7500 will be the limiter.

It's hard to say exactly where a 9800 pro would start to be heavily affected by a slow cpu. The thing is, having a fast video card can help out a slow processor and vice versa. I'd say below a 2500+ athlon or 2.4 p4 you start to become more heavily limited by your cpu, but that's just kind of a guess.

 

[Blastman]

It depends on the game and whether the game is very graphic card limited -- or very CPU limited.

Take for eg. test ? on a Duron 1.3 and the UT3 Botmatch. A GF4 MX440 gets 27fps and a 9700pro only gets 28fps. Very CPU limited. The game needs a lot of CPU power --- perhaps to drive the artificial intelligence.

The Aquanox game on the other hand scales very well with faster and faster graphic cards even on a Athlon 1.0Ghz ? thg?
?Very graphic card limited because for the most part going to a faster CPU hardly gets you anything. In this case going from an Athlon 1000 to an Athlon 2700+ yielded virtually no additional frame rates on most of the cards and very little on even the high end cards.

 

[Jeff7181]

Think of it like this...

The CPU has to process the information before it can be sent to the video card to have it rendered... if the CPU can't send it any faster, the video card can't render it any faster.