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DDR2 bottleneck ? Radeon 5870 vs. 6970 no fps improvement.

Last response: in Systems
January 19, 2011 11:01:45 AM


I want to share with you some bizarre benchmark results on my old build.

CPU: Intel Quad Q9650 @3.8 GHz
MOBO: Gigabyte EP35-DS3R
RAM: 8GB (4 x 2) PC2-6400 @ 840 MHz 5-5-5-16

Until recently, I've had 1GB Radeon 5870.

I was stuck in some games (GTA IV, Gothic 4) at average 25-35 fps on triple monitors 2 x 1680x1050 Eyefinity, no matter what internal game & catalyst 3D gfx settings I chose.

Sometimes I suffered fps drops to 15-20 fps.

GTA IV benchmark @ 5396 x 1050, GFX settings @high,

Radeon 5870 OC @ GPU 900 MHz / Mem 1250 MHz

Average FPS: 32.25
CPU Usage: 67%
System memory usage: 67%
Video memory usage: 95%

Seemed to me like I need more VRAM as there are CPU & memory reserves.
So I upgraded to 2GB Radeon 6970.

Now, surprise:

Radeon 6970, stock clocks, 2GB

Average FPS: 28.58
CPU Usage: 66%
System memory usage: 47%
Video memory usage: 42%

Even less fps !
How is it possible, that I have lot of unused CPU, GPU, VRAM, that game fails to use to improve performance?!

Some more details:

- GTA IV Multithreading works OK on Intel Quad, no core is used @100%, they stay in 50-80 % range.

- When I disable shadows in GTA IV totally, there is 10-15 fps improvement.

- Gothic 4 shows on 6970 exactly same low performance as before - stuck @ 30 fps.

- some other games run now in Eyefinity much better, some don't.

- Radeon 5870 benchmark was made @ 4GB 1080 MHz DDRAM2. Had to reduce DDRAM MHz after I added
another OCZ DDR2 PC2-6400 Reaper CL4 4GB. Old kit overclocked much better.

There must be some bottleneck. Probably has to do with RAM, is there a way to test it ? Some software to log amount of RAM transfers/RAM channels usage?

Do you have any other ideas ?

PS. Sorry for my bad English, is not my native language.
a b B Homebuilt system
a b à CPUs
January 19, 2011 12:11:35 PM

benchmarks show the 6970 only about 8-10% faster than a 5870, but, should be faster in all benchmarks....

I'd recommend a clean install, latest mb chipset drivers, latest AMD driver package....
January 19, 2011 12:30:01 PM

I have all the latest drivers.

I'll return 6970 and try with 5970.

Question remains, how is it possible that in GTA IV CPU & GPU & memory usages are about 50-80 % but framerate stays poor.

Game has to wait for something between between frames, but what for ?

My guess is memory transfers.

I will post 5970 benchmark today.

If this card won't help, I will build a new Sandy Bridge. My socket 775 build is so old, it is marvelous that all this years it served so well.

Until I bought 2 more monitors and entered triple screen world of Eyefinity .

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January 20, 2011 9:50:31 AM

Switched to Radeon 5970.

Game runs differently : I have fps drops ONLY when I turn around for the first time, or drive fast through city (probably when new textures are being transfered to VRAM).

When I stay in one place fps rate is much higher on 5970 then on 6970.

Seem logical - 2xGPU, 2 x 1 GB VRAM vs 1 GPU, 2 GB VRAM.

Basically, in 6970 there were less fps fluctuations.

Sadly, GTA IV benchmark shows about 28-30 fps average on both cards.

As there is massive fps gain when I disable shadows, without GPU usage change, I suspect that GTA IV has some own build in shadow processing system that need lot of data transfers, as GPU & CPU are not used in 100%.

I just ordered :
- I5-2500k
- GA-P67A-UD7
- OCZ DIMM 8 GB DDR3-2000 Kit

We'll see, how this will help.

Next step could be changing the 5970 to 4GB version & or going Crosfire.
a c 103 à CPUs
January 20, 2011 9:56:17 AM

GTA is poorly coded so not the best thing to make comparisons on.
a b B Homebuilt system
a b à CPUs
January 20, 2011 10:57:12 AM

I take back what I said.