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Where is this bottleneck?

S

st8ic

n00b
Joined
Feb 12, 2012
Messages
21
Specs are in my sig. I realize that 7770 crossfire is not a good idea in general, but I've been chasing this issue around forever. I'm running the 13.4 drivers and the latest CAPS.

  • GPU usage is 50%-60% in most games at 1920x1080.
  • GPU usage is 100% in indoor environments, or when looking at the ground. Turning down graphical settings does nothing.
  • CPU bottleneck? CPU usage in these situations is 40%-60%, but hard to estimate due to hyperthreading.
  • VRAM ceiling? These are 1Gb cards. All tools report my VRAM usage as 1.6-1.7GB out of 2GB (!?). Reducing VRAM usage with settings does nothing.
  • Bandwidth issue? Card 1 is running at 16x PCI-E 2.0. Card 2 is running at 4x PCI-E 2.0.

Why is my GPU usage so low? This happens in virtually every game, except Dirt 2 and some areas of Metro 2033.
 
what game?

some games are poorly optimized, and that just happens.

also, crossfire doesnt scale to 100% in some games.
 
The Mac said:
what game?

some games are poorly optimized, and that just happens.

also, crossfire doesnt scale to 100% in some games.
Click to expand...

Pretty much every recent game... for example, Saints Row the Third, Dirt Showdown, Hitman Absolution....

I know that Crossfire doesn't scale 100% in every game, but it's barely even trying in any game. Heaven 3.0 brings it to 100%.
 
that does sound unreasonable.

If heavan maxes both to 100%, then the cards and drivers seem to be fine.

Id start pointing the finger at your CPU.

Technically, you are running a dual core proc.

Most modern games multi-thread and use 4 cores.

push your CPU OC to the max, and see if you get better utilization. If so, thats your bottleneck.
 
Unfortunately, can't overclock even the bclock on this motherboard. I've checked per-thread CPU utilization with Process Monitor and the highest thread tops out at 20%, which means it's only using 80% of one core. So I doubt it's a CPU bottleneck?
 
not nessisarily.

its an i3, 2 cores, and low cache...

that having been said, check your pcie buss..

gpu-z can test it for you, make sure you are getting 2.0 speeds...
 
I checked my bus speed and they are indeed working at PCI-E 2.0 16x and 4x respectively.

When I disable crossfire, I get the same framerate. If it's a CPU bottleneck, that would imply that an i3 2120 is incapable of pushing more GPU than a single 7770.
 
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that appears to be the issue.

I know people with core2duo's are having bandwidth issues. Theoretically, an i3 should be better, but i just dont think 2 cores, or the reduced cache is enough for modern games.

The fact that Heaven pushes it to 100% just reinforces this as it is intentionally very light on cpu usage.

you might want to splurge on an i5

as a side note, does cranking up AA increase usage at all?
 
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My gpu usage does not hit a 100 percent unless its sleeping dogs or Crysis 3 both maxed out...

Tomb Raider on the other hand only hits between 50 - 65 percent scaling, Its not the best optimized game for the pc and crashes when trying to enable 2 or 4 x MSAA

I did notice my cards scaling higher when turning off v-sync for Dirt 3, try that and see what happens. (I am also going from 60fps to over 100fps)
 
you are also using an i7

hes got an i3

yes, turning off vsync will increase usage.

So will leaving it on, and turning on triple buffering.
 
st8ic said:
These are 1Gb cards. All tools report my VRAM usage as 1.6-1.7GB out of 2GB (!?). Reducing VRAM usage with settings does nothing.
Bandwidth issue?Card 1 is running at 16x PCI-E 2.0. Card 2 is running at 4x PCI-E 2.0.


Why is my GPU usage so low? This happens in virtually every game, except Dirt 2 and some areas of Metro 2033.
Click to expand...

I don't think two 1GB cards give you a total of 2GB VRAM, but it does sound like the CPU is causing the issue. Try cleaning out all drivers for the gpus and starting a new.
 
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