GTA IV and an ATI 4870 X2 - How do I know that it's using both GPU's?

[RandysWay]

Hello everybody,

I just got my new rig built and I'm coming from an ATI 9700 Pro, so I've never used Crossfire, SLI, etc. before so I am new to all of this. I'm running an ATI HD 4870 X2 (Full PC specs in sig) which has a total of 2GB memory.

In the GTA: IV Graphics settings, it shows:

Resource Usage: 976 / 1007 MB

I am assuming this is the video card memory. If it was using both GPU's in the 4870 X2, wouldn't it be closer to 2000 MB? Lastly, since the 4870 X2 has 2 GPU's, it's considered Crossfire, right? If so, do I have to set anything up special to enable Crossfire on certain games to work correctly?

I'm running GTA: IV at 1920x1080 on High settings and benchmark at a little over 60 FPS.


Thank you to everybody for your help!
-R

 

[Brownstone]

I use GPUZ, just open 2 GPUZ and u can select which GPU to monitor...
I think its pretty accurate

 

[GenBanks]

There is theoretically 2gb of memory, but crossfire / sli systems do not pool the memory from both gpus together. So the memory maximum will be the maximum from each single gpu, just as it would be if you had two separate cards. Nor to my knowledge does the 4870x2 require manual selection of crossfire in order to activate the full performance.

 

[Frostex]

ATI added a new tool to their drivers, if you right click the CCC system tray icon, expand the primary display card there should be a setting you can toggle called something like "Show Crossfire Status".

When you run games and crossfire is working you will get an ATI icon in the corner of the screen, goto the same menu and untick to disable it once you've confirmed crossfire is/isn't working, it should be working just fine for GTAIV.

GenBanks is right on the money, with SLI and Crossfire each GPU needs its own dedicated memory which holds an identical set of data to all the other GPU's, so a 2Gb 4870 X2 has 1Gb of vRAM per GPU but both banks of 1Gb hold the same data, effective memory size is 1Gb still, the game is reporting correctly.