2 X 7950 -- Bottleneck a 8350 @ 4.5GHz? (Pls. Advise or Predict)

Aderes Devorah · 19 Oct 2013 at 01:43

Hi all

Hope a good percentage of you are well

I'm just looking for advice from people who have this set up (or close to it) and/or wise words from those who don't have this set up but know their stuff.

Simple question... If I bought another 7950 (due to new low prices) and crossfired them, would you expect my 8350 to struggle?

The old silicon lottery seems to have given me a decent 8350 as it can go higher than 4.5GHz quite easily.

I know it ain't an exact science... so what do you say?

Best

kefan77 · 19 Oct 2013 at 01:55

I say go for it. CPU will be ok.

evohicks · 19 Oct 2013 at 02:03

kefan77 said:
I say go for it. CPU will be ok.

I have a similar setup but with the Sabertooth R2.0 and 2 x 7970's. They perform well in benchmarks and I have run my 8350 @ 4.7ghz stable but I have no need for that atm so its just a small O/C of 4.4 right now. They all run sweet, I had BF4 running ok with the odd stutter until I realised my power setting was on powersaver lol.
Go for it!

Martini1991 · 19 Oct 2013 at 08:47

It'll bottleneck.

But it's not going to give you unplayable frame rates, you just won't be getting the full benefit of them (And likely to perform as though you've got a lower set up, say closer to a 7870 Crossfire or whatnot)

Although this is more gaming side as opposed benchmarks (Synthetics I mean) as most games will have half your CPU twiddling its thumbs.
In future games, the bottleneck is going to become less and less (But obviously we can't actually say for definite how it'll end up)

Phixsator · 19 Oct 2013 at 09:13

Aderes Devorah said:
Hi all

Hope a good percentage of you are well

I'm just looking for advice from people who have this set up (or close to it) and/or wise words from those who don't have this set up but know their stuff.

Simple question... If I bought another 7950 (due to new low prices) and crossfired them, would you expect my 8350 to struggle?

The old silicon lottery seems to have given me a decent 8350 as it can go higher than 4.5GHz quite easily.

I know it ain't an exact science... so what do you say?

Best

Martini1991 said:
It'll bottleneck.

But it's not going to give you unplayable frame rates, you just won't be getting the full benefit of them (And likely to perform as though you've got a lower set up, say closer to a 7870 Crossfire or whatnot)

Although this is more gaming side as opposed benchmarks (Synthetics I mean) as most games will have half your CPU twiddling its thumbs.
In future games, the bottleneck is going to become less and less (But obviously we can't actually say for definite how it'll end up)

I ran crossfired 7950s for a long time on my FX-8350. At 4-4.4ghz the general GPU usage of both gpus was 50-55% in BF3 64MP (the only game i know of that would cause such a low GPU usage). When i OCed to 4.8 the usage on both GPU went up to around 60-65%. This is minimums btw, a lot of the time the GPU was much higher and near 80-90% for both OCs.

The rest of the games i played usually didnt have this issue and would yield pretty good GPU usage overall.

Things are likely to change if you are going to play BF4 due to Mantle(we hope) and if it does then the next year or so looks really good for Frostbite games s hopefully the CPU will be less of a bottleneck. Only time will tell

To sum up:
Will your FX-8350 struggle? No
Would i buy an extra 7950? No
Why not? The extra heat has to be managed somehow and unless its a gfx that vents the heat outside the case through the back i cannot see most pc cases to be very effective with a CPU air cooler inside as well unless you spend some good money on quality intake and exhaust fans(and they are pricey).
What would i do instead? I would OC the current 7950 i have to 1100 core and 1400-1450 memory using Afterburner and keep that OC once stable as a secondary profile for when games gets demanding. That should give a fair bit of free extra performance and most 7950 should be capable of this(37% OC on air is not bad at all).

Panos · 19 Oct 2013 at 09:43

My FX8350 works fine at 4.9Ghz under water, pushing the two 7950s PCS+ running at 1100/1550. Have yet to see a CPU bottleneck affecting performance, except is game using a single core (WoT for example)

almighty15 · 19 Oct 2013 at 11:20

It'll work but you'll be CPU limited.....

arc@css · 19 Oct 2013 at 12:08

As directly above, it will work and you will get plenty of extra frames in many games, but you won't be getting full value from your purchase. Personally, I'd probably take a look at the reviews for the 290 when it finally shows. Or, as suggested, take an in depth look at overclocking your current card.

almighty15 · 19 Oct 2013 at 12:45

This is from a thread I did on overclock.net

2500k at 4.6 with 7950 Crossfire

8 core FX CPU at 4.5Ghz with 7950 Crossfire

That was from the CPU benchmark which isn't that CPU heavy, the GPU benchmark showed a much bigger difference between the CPU's.....

The FX is playable at 40fps but in some levels it will drop to 30fps or below....

Martini1991 · 19 Oct 2013 at 12:58

Phix, I can't tell if you were agreeing with me lol.

Aderes Devorah · 20 Oct 2013 at 00:05

Nice one.

Aderes Devorah · 20 Oct 2013 at 00:06

Cheers. I went through my own BIOS recently and made sure all the ASUS options were turned off.

Aderes Devorah · 20 Oct 2013 at 00:09

Martini1991 said:
It'll bottleneck.

But it's not going to give you unplayable frame rates, you just won't be getting the full benefit of them (And likely to perform as though you've got a lower set up, say closer to a 7870 Crossfire or whatnot)

Although this is more gaming side as opposed benchmarks (Synthetics I mean) as most games will have half your CPU twiddling its thumbs.
In future games, the bottleneck is going to become less and less (But obviously we can't actually say for definite how it'll end up)

Interesting... I may stick as I am or wait to see what 680 prices are like.

Aderes Devorah · 20 Oct 2013 at 00:13

Many thanks for the comprehensive answer. I have Afterburner (better than ASUS Tweak) so I'll create a higher spec profile.

Aderes Devorah · 20 Oct 2013 at 00:16

Yes, I may well do that. I just watched Tom Logan's Oc3D video on the new AMD cards, and he says that they are basically not much more than a rebrand and advised crossfiring instead of going for a 290. Thanks.

Aderes Devorah · 20 Oct 2013 at 00:18

Nice. Thank you.

TropicLightning · 20 Oct 2013 at 00:30

Aderes Devorah said:
Hi all

Hope a good percentage of you are well

Best

Why not hope all of us are well?....I hope you are well...lol

Or are there certain ones of us you don't wish well... and who are they...lol

gpuerrilla · 20 Oct 2013 at 00:44

Why are you guys not posting on the *** official AMD 83X0 overclocking thread *** [CPU]?

I cant believe some of us are pushing 5Ghz and discussing in the thread with lesser GPU's yet people have them smoking a pipe and wearing slippers at 4 to 4.4ghz with crossfire 7950's!

gpuerrilla · 20 Oct 2013 at 00:50

Martini1991 said:
It'll bottleneck.

almighty15 said:
It'll work but you'll be CPU limited.....

Panos said:
My FX8350 works fine at 4.9Ghz under water, pushing the two 7950s PCS+ running at 1100/1550. Have yet to see a CPU bottleneck affecting performance, except is game using a single core (WoT for example)

The guy who has this setup says it is not bottlenecked, I know one of the above does not own the FX-8 and says it will. What gives?

alex_123_fra · 20 Oct 2013 at 02:06

We've sort of been through this elsewhere. The correct answer is that in well threaded games which utilise all 8 cores, you will not see bottlenecks (eg Crysis 3). Unfortunately the majority of games are not like this at present. Over the next 1-2 years, you are highly likely to see games utilise all cores hence bottle necking will become far less relevant at least for another gpu generation.

Edited to say, obtaining overclocks of 4.8GHz+ on these chips is almost guaranteed so that helps a lot.