Can someone explain CPU bottleneck?

[zhwu]

I don?t understand how CPU bottleneck affects high end video cards and want to get some ideas from here.

I only play strategy games and my 3 years old althon64 X2 4200 machine with an ATI 1900GT card has been solid for that task over the years. However, the new game ?Empire: Total war? is killing that machine at 1680x1050 resolution and I need to do a video card upgrade very soon.

Since frame rate is not that important in strategy games (compare to shooter games at least) Can someone explain to me what will happen if I put a good video card such as 4870 into this machine? Will I be seeing detailed graphics with very low frame rate? (how low can the frame rates go?)

I read somewhere that CPU bottleneck is not as bad as most people think. Yes, it will cap the FPS in benchmark testings; but I don?t really need super high FPS in my games. (Just want to see very detailed graphics at 1680x1050 with reasonable refresh rate.)

I am thinking about doing a 4850 or 4870 upgrade (without OC the X2 4200 CPU)
Please let me know if you think such an upgrade will be a waste.


ps: will the release of 4890 & GTX275 lower the price on the current mid-end cards (4850,4870, 260 core 216) in the next 1 ~ 2 weeks?

 

[Lonyo]

If you get a faster graphics card, you usually will be able to increase detail settings up to a point without any FPS hit (because your maximum FPS is being determined by your processor), so basically yes, your frame rate will remain approximately the same (assuming the graphics options you turn up don't increase CPU requirements at all), but your detail settings will be improved.

Prices for existing cards have already dropped/been dropping recently. The new cards are coming out at the prices the old cards used to be ($250), so don't expect any price movement from the HD4850's GTX260's etc, they are already fairly settled in their new price points.

If your frame rate is acceptable for you currently, then a new faster card will allow you to increase details with minimal frame rate reduction, assuming that you are indeed CPU limited.

 

[toyota]

with that cpu there is no point in putting a really fast card in that system. a 4830, 4850, or gts 250 would be the very highest I would go. although you still want get all the performance those cards can offer it will be a huge upgrade.

every game is different but a cpu can make a huge difference depending on the res and video card being used. the faster video card you get the more cpu you need to keep it happy especially below 1920. for instance with my e8500 at 2.66 and a gtx260 I will get almost identical framerate in Far Cry 2 no matter what res I run at. that means have a faster card at 1920 or below in that game will not really help without also having a faster cpu.

 

[zhwu]

Right now, the frame rates are OK (to my eyes) when I config my graphics setting to low at 1680x1050. If I turn up the graphics setting to medium, then it become really slow. ( my current graphic card is obviously the bottleneck at medium settings)

Can I safely assume with a good video card, I should be able turn up my graphics to high @ 1680x1050 and still have the same or better frame rates I am currently getting at the low setting?


I plan to use this machine to play (strategy) games for another 1 ~ 2 years. I was thinking about 4870 and gtx260 only because they are a little bit more future proof (with more Video ram) Anyway, looks like a 4870 will be too much of an overkill for my processor and I should settle with a 4850 instead?

 

[toyota]

Originally posted by: zhwu
Right now, the frame rates are OK (to my eyes) when I config my graphics setting to low at 1680x1050. If I turn up the graphics setting to normal, then it become really slow. ( my current graphic card is obviously the bottleneck at medium settings)

Can I assume with a good video card, I should be able turn up my graphics to high @ 1680x1050 and still have the same or better frame rates I am currently getting at the low setting?

most certainly coming from that card to a 4850 or so. anything more than a 4850 will likely result in little to no benefit though. that cpu is pretty slow but with a 4850 or so at 1680 it wont be too much of an issue.


holy cow can this be right? even a fast cpu can barely run the game and a slow cpu cant even get out of the single digits. http://www.dvhardware.net/article33885.html

 

[taltamir]

FPS = frame per second. each frame takes so many miliseconds (ms) to render, 1000 ms make up a second... every 1000 second the amount of frames rendered in that time period is added up and it gives you your fps. (well technically you divide 1000 by the ms to render each frame to give its instantanous FPS and then you average those).

There are two types of calculations, sequential, and concurrent:
1. Sequential calculations examples:
CPU takes A ms to perform a task, then it gives it to GPU to finish, gpu takes B ms... total time to finish that task was A+B ms. if that is the task that takes the longest to complete in a specific frame, that the time to render that frame will be A+B.
If your CPU takes lets say, 50ms to finish it and the GPU takes 2ms... then doubling the GPU speed will reduce your time to render from 52 to 51ms... while doubling the CPU speed will reduce it from 52 to 27ms. you would say that is CPU limited.
If your GPU takes 50ms and the CPU 2ms.. then the opposite applies.
If the CPU takes 50ms and the GPU takes 50ms to finish it, than doubling either one will give a solid improvement, and you are said to be balanced (not GPU or CPU limited)

2. Concurrent tasks
The CPU has to perform some tasks unrelated to the GPU (say, AI calculation)
The GPU has to perform some tasks unrelated to the CPU (well actually its more like tasts that take a tiny bit of CPU and lots of GPU, like say, 2ms CPU and 50ms GPU).
If the CPU task takes a lot longer than anything else to calculate, than it is the limiting factor, it doesn't matter how much faster the GPU gets, the GPU cannot start drawing the next frame because it doesn't know WHAT will happen in the next frame (is the AI going to shoot at you? move? duck?). You are then CPU limited.
If the GPU task takes a lot longer than anything else to calculate, than it is the limiting factor, it doesn't matter that the CPU has already calculated what the AI will do for the next 10 minutes... the frame is not finished because the GPU is still calculating the light reflection on his pistol.

Note that 1 and 2 are not seperate... What is holding you back can be ANY of the situations described in 1 or 2... Note also that those can DIFFER from frame to frame... so for frames 1-20 for example you could be GPU limited because the GPU is calculing light reflections of a gun slowly... then suddenly you cast a spell that causes the CPU to drop its current AI plan and redo all of it... it cannot even begin to render the next frame until it KNOWS what is going where, so it can lead to a "stutter", a long period of time where the GPU is simply waiting for the CPU to tell it what to do next.

 

[zhwu]

holy cow can this be right? even a fast cpu can barely run the game and a slow cpu cant even get out of the single digits. http://www.dvhardware.net/article33885.html

Wow I have no idea this game is so demanding on the processor. Hmm, maybe I should re-consider my upgrade decision. Even with a 4850 upgrade I doubt I will be able to play the battle at high (not the highest) resolution. Spending $150 so I can play a game at medium setting instead of low is not worth it to me and I can't afford to upgrade my entire machine for 1 game at this point.

At the very least the battles feel smooth to me at low setting right now. Need to convince myself that graphics are not important in strategy game. (although it feel odd to control lines of black human shades shooting bullets at each other on the battle fields

 

[Lonyo]

Originally posted by: toyota

Originally posted by: zhwu
Right now, the frame rates are OK (to my eyes) when I config my graphics setting to low at 1680x1050. If I turn up the graphics setting to normal, then it become really slow. ( my current graphic card is obviously the bottleneck at medium settings)

Can I assume with a good video card, I should be able turn up my graphics to high @ 1680x1050 and still have the same or better frame rates I am currently getting at the low setting?

most certainly coming from that card to a 4850 or so. anything more than a 4850 will likely result in little to no benefit though. that cpu is pretty slow but with a 4850 or so at 1680 it wont be too much of an issue.


holy cow can this be right? even a fast cpu can barely run the game and a slow cpu cant even get out of the single digits. http://www.dvhardware.net/article33885.html

As is mentioned, that's absolute worst case scenario, so it's likely real world use will never even come close to that.

 

[cbn]

What program can measure frame rates in a game?

NVM I just found FRAPs.

Thanks

 

[BFG10K]

The simplest way to test for a CPU bottleneck is by raising your resolution and/or AA level. If your performance doesn't reduce by doing this, you're CPU limited. If it does, you're GPU limited.

This test works because CPU load remains constant regardless of resolution or AA level.

 

[alcoholbob]

Strategy games (and RPGs) are particularly CPU limited. GPU does its work on the things the CPU tells it to. When you are dealing with tons and tons of units, the GPU is waiting for the CPU to send the data on all these units...hence, the CPU is the bottleneck.

 

[fourdegrees11]

Does your motherboard support AM2+ CPUs? If so you might want to do a cheap CPU upgrade like the 7750 Kuma for $68
http://www.newegg.com/Product/...x?Item=N82E16819103300

If not you could also do a cheap MB upgrade to a AM2+ micro ATX for $55.

http://www.newegg.com/Product/...x?Item=N82E16813157153

And then eventualy add a solid budget card like the 4830 for another $100 (or less if you wait a bit)

http://www.newegg.com/Product/...x?Item=N82E16814127420

edited for stupidity

 

[BladeVenom]

Originally posted by: fourdegrees11
If not you could also do a cheap MB upgrade to a AM2+ micro ATX for $55. The onboard video is better then your GPU.

http://www.newegg.com/Product/...x?Item=N82E16813157153

I think you overestimate what integrated graphics can do.

 

[alcoholbob]

Way over estimated. the 1900 was a $300+ video card a few years ago. Integrated graphics can barely run Warcraft 3.

 

[toyota]

Originally posted by: Astrallite
Way over estimated. the 1900 was a $300+ video card a few years ago. Integrated graphics can barely run Warcraft 3.

yeah that onboard 3200/3300 graphics are about like a 2400xt which is less than half the performance of the x1900gt.

 

[LN2009]

A way of checking if it's your CPU causing the bottleneck is lower details settings, if framerates remain relatively stable despite lowering the requirements the bottleneck is not your graphics card.

I have the same problem in WoW, used to be able to run 1920x1200 no problems now my frame rate is in the 30's on a good day and below 10 on a bad.

I upgraded the CPU and old 939 2.4Ghz to a Kuma 7750 2.7 and gained 20 fps, overclocked the Kuma to 3.0 and gained another 20.

It seems we've come around again with games requiring more CPU brute force and less GPU.

 

[zhwu]

Thanks for all the inputs here, my motherboard does not support AM2+ (only AM2) so CPU upgrade options are very limited.

I am just trying to figure out if I can get another 1 ~ 2 years out of this machine by doing a video card upgrade. In general, I don't like doing CPU & motherboard upgrades. (would rather build a new machine and give the current machine away to family members) Seems like I better hold off any upgrades on this machine and build a new i7 system maybe 6 ~ 9 months down the road.

 

[TurtleCrusher]

The 5600+ for $72.99 would be a really good upgrade.

You should really look in the for sale/for trade part of this forum. A lot of people are selling of their X2's after they bought their new Phenom 2s.

EDIT: Newegg Link http://www.newegg.com/Product/...x?Item=N82E16819103234

 

[Schmide]

There is something seriously wrong with that game. For a turn based strategy/pseudo real time tactics game to get 15fps max on top of the line hardware is just crap.

 

[SickBeast]

Originally posted by: zhwu
Thanks for all the inputs here, my motherboard does not support AM2+ (only AM2) so CPU upgrade options are very limited.

I am just trying to figure out if I can get another 1 ~ 2 years out of this machine by doing a video card upgrade. In general, I don't like doing CPU & motherboard upgrades. (would rather build a new machine and give the current machine away to family members) Seems like I better hold off any upgrades on this machine and build a new i7 system maybe 6 ~ 9 months down the road.

Yeah you might as well max out your motherboard CPU-wise provided that it's cheap enough.

I would also invest in a good cooler and overclock it as high as it will go. You should be able to hit 3ghz+ on a newer stepping. With a CPU at that speed, you can pretty much go with any graphics card that you want.

 

[alcoholbob]

If you're feeling adventurous, your 4200 should net your about $100+ on ebay, add your mobo, video card, RAM, and whatever else you want to canabalize you can probably come out with about $250.

If you look at current prices, on newegg; E7400 + mobo + DDR 2 1066 RAM comes up to $250.

Which is to say -- sell it while it still has value.

I had the exact same system you had (4200 939 system with 2 gb cas 2 ddr1 ram and 8800GT, 200GB IDE hard drive) and I sold that on ebay/craigs for a combined $360ish. I replaced it with a refurbished, low powered dell hybrid. If you want it for your relatives, you're probably better off giving them a video card + $250 in cash and you'd get a better gaming system than what you are running now.

 

[TurtleCrusher]

Originally posted by: Astrallite
If you're feeling adventurous, your 4200 should net your about $100+ on ebay, add your mobo, video card, RAM, and whatever else you want to canabalize you can probably come out with about $250.

If you look at current prices, on newegg; E7400 + mobo + DDR 2 1066 RAM comes up to $250.

Which is to say -- sell it while it still has value.

I had the exact same system you had (4200 939 system with 2 gb cas 2 ddr1 ram and 8800GT, 200GB IDE hard drive) and I sold that on ebay/craigs for a combined $360ish. I replaced it with a refurbished, low powered dell hybrid. If you want it for your relatives, you're probably better off giving them a video card + $250 in cash and you'd get a better gaming system than what you are running now.

Might want to re-read the thread. It's socket AM2, not 939.

I'm saying $130 parted out, not $250.

 

[A5]

Originally posted by: Schmide
There is something seriously wrong with that game. For a turn based strategy/pseudo real time tactics game to get 15fps max on top of the line hardware is just crap.

That test is a maximum detail sea battle (and it's from the release version of the game - already been 3 updates) which is by far the most intense thing in there. This game will also use all the RAM you can give it.