How much of a decrease in performance do you get running 2x Radeon 7850s 1 in x16 mode another in x4 mode

Priva

Honorable
Nov 21, 2013
150
0
10,690
I have 2 Radeon HD 7850's in CF one is PCI Express 2.0 x16 slot (the main one) another is only PCI Express 2.0 in x4 mode. I know it decreases performance compared to a MB with x16/x8 or x16/x16 so percentage wise (in gaming) how much would it affect my FPS 10% 20%? Because It's still better using both cards rather than one card even though I'm in X4 mode (I hope) and I'd like to keep my setup but if it's like 50% decrease in FPS using x4 mode than x16 for the second slot I mind as well sell both GPUs and get a single one. If it's only 10% decrease in FPS because of the x4 mode however, that's not a big concern to me because it still functions at least 90%

Motherboard: Asus P8Z68-V LE
Processor: Intel Core i7 2600k OC 4.3GHz
 
Solution
I would approximate 10% or less.

easy way to see if it's worth it, run 3d mark and note down your score with 2 cards, remove 1 card and run it again.

if 1 card is 10,000 points and 2 cards is 15,000 or more i would keep the card in.
(NOTE: even with x16/x16 adding a 2nd card will NOT double your 3d mark score)

HugoStiglitz

Distinguished
I would approximate 10% or less.

easy way to see if it's worth it, run 3d mark and note down your score with 2 cards, remove 1 card and run it again.

if 1 card is 10,000 points and 2 cards is 15,000 or more i would keep the card in.
(NOTE: even with x16/x16 adding a 2nd card will NOT double your 3d mark score)
 
Solution

Priva

Honorable
Nov 21, 2013
150
0
10,690

I am using these settings:
http://puu.sh/6kfvo.jpg

Good thing I have 3DMark. I will run the test now and tell you what my score is. With one card and with 2 cards. Should I use Extreme settings for the tests?
 

HugoStiglitz

Distinguished
dont run extreme we just want to get an idea, leave the settings on default. (DONT USE CUSTOM)

also, actually remove the 2nd gpu, this will give a true full bandwidth test to a single card.

coil wine can happen, it sound like clicking coming from your graphics card. nothing to worry too much about.
 

Priva

Honorable
Nov 21, 2013
150
0
10,690
Ok. I ran the test on default settings (just hit run fire strike) removed the GPU and put it back in did the same thing here are the results:
1 GPU: http://puu.sh/6kirh
2 GPU: http://puu.sh/6kjNn.jpg
So +1229 score for the second GPU

It seems the FPS is better using a Single GPU in Combined, Physics and Graphics Test 2
but using both strangely the FPS doubles in Graphics Test 1 but is slightly lacks the other tests compared to 1 GPU but overall It seems the FPS was better I guess during testing. What do you think of all this?
 

HugoStiglitz

Distinguished
this is correct, and you will see in real world games some games will indeed give you better performance running both in CFX, however other games you may find the overhead of the 2nd graphics card costs more than the 2nd card gives in performance.
normally all games written by the same developer will behave the same.

this is why its normally recommended to stick with a single card unless you already have a top of the range card and want even more performance. (7970, 290x, gtx 680, 780 & etc)

as the lower cards just don't stack up as well in dual arrangements.

Make sure you have the latest catalyst drives from AMD/ATI's site,
 

Priva

Honorable
Nov 21, 2013
150
0
10,690


Thanks for the information. I will stick with the 2 cards for now because the tests results show it's better in CF however many games I played didn't support crossfire such as CoD Ghosts. Which means I would have to disable it and get bad FPS trying to max the game using 1920 x 1080 resolution. I will probably sell the cards and go for the GTX 770 because I heard some good things about it. Apparently, it's 12% better in performance according to this site than 2 7850's in CF mode.
http://www.game-debate.com/gpu/index.php?gid=1564&gid2=881&compare=radeon-hd-7850-crossfire-vs-geforce-gtx-770

Being a single GPU I won't have to deal with microstuttering or any other multi-gpu related problems.

I'll keep what I have for a few more months maybe something even better will come out or the prices will drop