CPU or GPU for AH?

[MANDO]

I'll try to make the question as simple as possible.

Which would be the CPU power from where more power will not give you more FPS in AH?

What is the CPU MHz limit from where GPU power is the very only source of extra FPS?

I know that some graphic card/driver sets are more CPU dependant than others. Lets consider we are using the finest possible graphic card/drivers set.

[jonnyb]

Assuming the best graphics card, the obvious answer is the better the CPU, the more frames you get.

That is the simplest case.  Since AH is so CPU dependent, the more horsepower you've got, the better and smoother the game will play.  Of course, I'm assuming you have top-of-the-line components all around (at least 1g memory, fast drives, good MB, etc) and that the only variable here is the CPU.

So, what is the best CPU?  IMHO it is the FX-55.  Combine that with a pair of 6800 ultras in SLI and you'll have the best gaming rig on the planet.

[MANDO]

Originally posted by jonnyb
Since AH is so CPU dependent

Are you sure of that? 3GHz would make any noticeable difference over 2 GHz?

[Balsy]

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Originally posted by eagl
I've found that AH stresses my computer more than the benchmarks do, so an otherwise stable overclock will often result in a blue-screen crash when running AH. Dunno why, but that's what happens. I'm having to completely re-run my overclocking stability tests to determine whether it's my cpu or ram.
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Easy. Flight modeling requires an enormous amount of floating-point calculations. There is not an FPS game on the planet which comes close to what is required of a good flight simulator in terms of floating-point calculations required per frame.
Floating-point calculations are what drives the CPU temperatures up the most.


__________________
Roy "Skuzzy" Neese
support@hitechcreations.com

[MANDO]

So, if flying a plane someone get 90 fps while looking to the sun and 30 fps while looking to the ground we may conclude that the sole problem is the GPU and that the CPU is more than enough for the flight model?

[Skuzzy]

It's not that simple.

The video card can only do so much.  But in order for it to be able reach its pontential, the CPU has to get the data to it.

Most people think buying a high end video card buys more frame rate.  The truth is, it buys more *potential* frame rate.

The CPU ends up governing it all as it is still responsible for getting the data to the video card.  Which means it has to crunch through all the flight model information and then get the data to the video card.

[jonnyb]

Originally posted by MANDO
Are you sure of that? 3GHz would make any noticeable difference over 2 GHz?

The short answer to your question is yes.  As Skuzzy explained, better GPU gets you more potential frames.  Better CPU gets you more of that potential realized.

Originally posted by MANDO
So, if flying a plane someone get 90 fps while looking to the sun and 30 fps while looking to the ground we may conclude that the sole problem is the GPU and that the CPU is more than enough for the flight model?

Not at all.  There are quite a few factors involved here.  Graphics settings, memory, cpu...they all play a part in this.

[humble]

Back in December my Barton core 2500+ went to the great beyond (cpu fan died while I was at work). I decided to go ahead and upgrade to a AMD athlon 64 (got a 3200+ 754 on DFI lanparty board)....

Kept my Ti-4200....FPS jumped about 5 under "load" and about 10 in level flight up high....(all at default).

[Skuzzy]

In the case you just mentioned humble, it sounds like you hit the performance wall of the video card.  It's not necessarily a bad place to be, however a better place is to have not be hitting the performance wall of the video card.
It is better to have too much GPU rather than too much CPU.

Right now, the fastest CPU available cannot push the high end cards from ATI/NVidia to thier fullest performance.

[MANDO]

Originally posted by humble
Kept my Ti-4200....FPS jumped about 5 under "load" and about 10 in level flight up high....(all at default).

This is an excelent example, jumping from a Barton 2500 to a 64 3200+ and getting only 5 fps more near ground. I would even say these 5 extra fps (or 10 up and high) were more related to the new architecture (chipset) than to the extra CPU power.

What would be the effect of replacing the old Ti-4200 for a 6600 GT or 6800 GT and keeping a healthy Barton 2500? Probably you would get far better results. And what about 6600 GT and Athon 64? May be only 5 fps more than with Barton+6600 GT?

Skuzzy, with the exception of texture transfer, what kind of big ammount of data should the CPU elaborate and send to the video card in the particular case of AH?

[Skuzzy]

Mando, it is not so much the amount of data, its all the calculations required to get the frame setup for the data.  All the flight modeling has to be done before the frame can even begin to be drawn.

I am being terse for a reason.  This is a very complex subject and I could write pages about it.  There is no simple answer to this and if you chose to try and use a simple answer, you probably will make an error.

The complexity comes in due to the dynamic nature of the game.  How it accomodates various options of video cards and so on.

[MANDO]

So it is not possible to conclude a maximum CPU power for AH from where any noticeable gain will come only from the GPU?

I find this is a very bad time to upgrade, this is a very personal oppinion after checking new techs like PCIe, true 64 bit OS in the near future, etc.

But, for sure, many others are about to upgrade their systems just to raise the performance to new AH2 requirements (not minimum). These can risk a lot of money in a system that will be really obsolete in less than two years, or just invest the minimum quantity of money to get very good results (60FPS as minimum at medium detail, for example).

Actually, the biggest risk is on MB (chipset) and CPU, while a good GPU may represent the lowest risk in the upgrade.

It would be very usefull to identify a limit in CPU power from where the FPS improvement will be minimum (no matter the GPU). This way players would have a clear idea of what to upgrade, CPU, GPU or both.

[eagl]

If you're scared of upgrading right now, wait until AMD releases their dual core cpus and see if they'll be drop-in upgrades to current socket 939 mobos.  If they are, prices on the older athlon 64s ought to drop like a rock making that a reasonably low cost upgrade path, with the option of upgrading to a dual core cpu later on.  That, plus a pci-e motherboard, would set you up with a very fast system that would accept both a cpu and vid card upgrade in a one or two year timeframe.  DDR memory is still as fast as DDR2 until they get the FSB up past 300ish mhz, so even that isn't really a dead end for another couple of years.

With Intel releasing it's plans for dual core cpus in 2005, I think we'll see some good prices for fast AMD systems this year.  If AMD doesn't mess up, they could sell a crapload of dual core cpus if they can just be dropped into existing socket 939 boards.

[MANDO]

Skuzzy, my english is phetid, so I will try to make reduce all to a very simple question with few "parameters".

Lets suppose the "more than enough" AH settings are all to medium detail, 512k textures and water effects. We want to keep a very minimum of 60 fps in any normal condition.

Now lets look for the best graphics card in the market. Lets say it is Nvidia 6800 GT (just an example).

Are we able to determine which processor will be able to do the job (60 fps with the described settings) with that card?

[Skuzzy]

The faster the CPU the better the game will run.  I am not just talking about graphics.

You cannot go wrong with a faster CPU, regardless of the video card.  However, in a best case scenario, you want to avoid having the video card hitting its performance wall.

Now, where is that wall at?  This is where it gets complex.  Humble hit it with his Ti4200, but those were simpler cards.  The new cards available today are significantly more complex.  Much more complex than the CPU.

My system at home is pretty balanced for Aces High II.  3.4Ghz Northwood CPU and an ATIX800XT video card.  The video card is fast enough to not be pushed to its limits with the CPU, and the CPU is fast enough to make the game run smooth as a hot knife through butter.

I would say Aces High works best with a 2.4Ghz CPU and higher, if you want an ideal performance environment.  BUT, that may not be enough if you crank all the details up.  You have to quantify what level of detail you want to run the game at in order to make any kind of guesses about the hardware requirements for that configuration.