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Crossfire 6950 x16 x4 ?

Ash576

Ash576

Ash576

Associate
Joined
14 Apr 2011
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32
Location
Bristol
Got my system all set up and planning to buy the final part, the graphics card. I am deciding to go for the new 6000 series and grab myself an ATI 6950 and then unlock it to a 6970. :D

I have 2 things that are on my mind though:

1. Are the 6950s still BIOS Locked and can still be flashed? Or have AMD started to Hardware lock them? I heard from somebody that they were starting to do that.

2. Also my motherboard is an ASUS M4A88TD-V EVO and does support crossfire, but only with one PCI running at x16 mode & the other at x4 mode. If I were to crossfire 2 6950s (unlocked to 6970) what would be the performance hit on the x4 lane? Would I gain much of a performance BOOST by dropping in a 2nd 6950 into the x4 lane? I have heard mixed reviews, but not any advice on the new 6000 series cards.

This is my 1st build and any help or advice would be widely appreciated :D
 
I've got a 6950 running at 70 and it is a very good card!

You can only unlock the revision 1 cards though (reference models with dual bios switch)

I have a similar mobo to yours with the same PCIe lanes problem. You would take a hit in performance crossfireing anything on that board as opposed to two x16 lanes but you would still get a lot of extra performance over one card.

Personally I'm going to upgrade to a 900 series chipset mobo later in the year which has proper crossfire support, and also wait for the prices to come down before I add another.

You don't need two if you are gaming at 1080p or below though, it is overkill (but would obviously be nice)

I hope that helps.
 
Remove the competitor link asap.

Posting links to companies with the same core buisness as OcUK doesn't go down well with the mods :)
 
but is there a noticeable performance increase with one card on the x16 and the other card on the x4 than just the single card?
 
I should hope so :P Otherwise that's like £200 down the drain. There will defiantly be an increase, but how much compared to one single card I do not know :/
 
If you look at the links posted earlier, you'll get between a 5-25% drop in fps when running in x16/x4 compared to running at x8/x8, depending on the game used.


Take the AVP benches@1920x1200 here. A single 6950 gets 57fps :

http://www.tomshardware.co.uk/pci-express-scaling-p67-chipset-gaming-performance,review-32164-4.html


Here it shows that 2x6950's in crossfire get 112fps at x8/x8, and 103fps when running at x16/x4 :

http://www.tomshardware.co.uk/pci-e...ipset-gaming-performance,review-32164-10.html


Exactly how much the 2nd card adds also depends on how well the game scales with crossfire. Some games will show up to a 95% increase in fps, whereas some show around a 50% increase.

You're not guaranteed double the framerate just because you have 2 gfx cards / gpu's.

Still, anything above 40-50fps is still regarded as very playable by most people, so not a great deal to worry about really unless you're running at 2560+ with >4xAA, or using a 3 monitor setup.
 
Different gfx / motherboard drivers ? Who knows.

It's a rough idea though I suppose & TH did say that NV cards didn't suffer the same level of fps loss compared to ATi cards.

I did try running 2x4870's in x16/x4 a few months ago & noticed my fps were around 10-15% lower when compared to a 2x4870 x8/x8 setup in the games I tried.
 
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