Topic Title: HD7970 crossfire dedicated memory video drop
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Created On: 01/06/2013 11:33 PM
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 01/06/2013 11:33 PM
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Hi all

I have been building my RIG for some time now, but I recently (Xmas) came across a second HD 7970 video card. very happy with the first video card worked great. I have built two other systems in the past first one was SLI which worked fine. this is the second build I have done and went with Crossfire. before purchasing the first HD 7970 I ran two HD 5750's in crossfire and this worked great for some time.

this time around though it's a different story. after installing the second 7970 I installed the latest drivers 12.10 which installed fine as well. also installed the latest CAP and after rebooting everything came up fine and crossfire started automatically. However after adjusting my screen I noticed that my dedicated video memory had dropped from 3GIG to 2GIG and the shared video ram had dropped 1GIG as well. after experiencing the dual 5750's which doubled my dedicated video memory before this made me question. even in SLI my dedicated video memory had doubled and worked great. I have another thread going at as well but everyone there says its working fine because GPU-z says that 2 GPUs are enabled. well that's true and it reports 3 gigs of ram for both video cards

I have removed and run driver sweep several times uninstalled both video cards and run them individually and purchased a new bridge and ran two bridges but nothing has made any change. even rebuilt my windows 7 install but still that same thing.

I don't experience many performance drops but with 1 HD 7970 I have better performance then with crossfire enabled.

My box

MSI-790FX-GD70 (MS-7577)

8 GIG low latency Memory (777) patriot

1KW power supply (green power)

965 black edition 3.4GHz proc


 01/07/2013 12:05 AM
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I don't experience many performance drops but with 1 HD 7970 I have better performance then with crossfire enabled.


And yes, it is working fine, I assume you are getting your memory information from DxDiag which is often wrong.

AMD FX-8350 w/ Corsair H105, ASUS Sabertooth 990FX Gen3/R2, 8GiB G.SKILL DDR3-2133, XFX HD 7970 GHz Edition, 1TB Samsung 850 Evo, 256GB OCZ Vector, Creative X-Fi Titanium w/ Creative Gigaworks S750, SeaSonic X750, Corsair C70, HP ZR2440w, Win 7 Ult Ed x64
 01/11/2013 11:45 PM
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Sorry been a bit busy and I re installed windows 7 x64 this last week end. but still the same results.

I experience a little bit of stuttering when I play games metro2033 I get some stuttering during cut scenes as well as on black ops II. during game play I don't see it very much at all. but when I turn off crossfire stuttering is none existent I don't see any stuttering on anything I do. 1 7970 works great everything is as smooth as smooth can be.

and no I did not get my info from DXDIAG the below picas will show what I am talking about.

I can see that crossfire is working in GPU-z and using CCC I can see that crossfire is enabled. GPU-z will report the memory working fine on both video cards voltage is working and I have pulled both cards and test them both individually with both cross fire power cables so no issues there.

I can see that things are working fine however my issue is this. when I had 1 HD5750 I was able to play games pretty well at that time after adding a second HD5750 I had a considerable performance gain. when checking the dedicated video memory this read double. this is the same board that those 2 5750s were installed on. I also have a ASUS A8n32-SLIDELUX board and ran dual 7600GT's on this and experience the same. this was my first build several years ago.

now with dual 7970's (VisionTek) after enabling crossfire my dedicated video RAM drops???? and I loose performance??? WT$ ok so I uninstall reinstall swap video cards change slots put them in slots 1 and 3 ( what the manual said) buy an new bridge use 2 bridges and still no change.

I have searched this problem all over the web but nothing this seems to be the first of this type of question that has ever been posted.

 sorry wont let me upload any files.

please see the pics at this web site

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