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Sapphire Radeon HD5870 + HD5850

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Hi community, I'm pretty sure you'll be able to guide me through my choice.

I currently own a Saphire RADEON HD 5870. I was looking at the 5970 performance and was quite impressed. Since I bought a new monitor (ASUS vw266h 2ms max res: 1920*1200) and want to get the maximum from my games at max resolution, I was wondering:

Would it be a good choice/idea to go Crossfire with a 5850 (120$ less than than a new 5870)

or go with a HD5970 and try to sell my HD5870.
BTW the HD5970 is back order in most of the computer store near me.
I know if I buy a 5970, ill need to change my case. The 5870 barely fit in and the 5970 is almost 1 inch longer.
This is the reasons why I'm tempted by a crossfire with a 5850 instead of buying a 5970 and wait a month before getting it


here my PC Spec in case you see somthing that could be a bottleneck for my 2 GPUs

Processor: I5 750
RAM: 4GO RAM
MoBo: P7P55D
PSU: 700W Coller Master SILENT PRO SERIES M
GPU: Saphire RADEON HD 5870
Case: Aspire X Super Alien Aluminum Case





More about : sapphire radeon hd5870 hd5850

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Graphics card Master

Which P7P55D? Make sure it can do dual X8.

A 5870/5850 Crossfire would be just a dual 5850 Crossfire, but if you OC the 5850 to 5870 speeds its another story.

Can you trade your 5870 for a 5850+cash? That seems like a good idea now.

(or you can opt for dual GTX460s, which performs ~5-10% worse than dual 5850s, draws a bit more power, but its only $450.)

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Graphics card Master

It is not a good idea in general to crossfire between different cards. When you do so essentially the better card turns itself into the weaker card. So when crossfired with an HD5850 the HD5870 will underclock itself to match the core speed of the HD5850 and disable 10% of it's shaders to match as well. If you are overclocking the speed part doesn't actually matter as both cards can easily be OCed to above the 850mhz stock setting for the HD5870 but you will lose the extra shaders on the HD5870.

jyjjy said:
It is not a good idea in general to crossfire between different cards. When you do so essentially the better card turns itself into the weaker card. So when crossfired with an HD5850 the HD5870 will underclock itself to match the core speed of the HD5850 and disable 10% of it's shaders to match as well. If you are overclocking the speed part doesn't actually matter as both cards can easily be OCed to above the 850mhz stock setting for the HD5870 but you will lose the extra shaders on the HD5870.


I did check a few benchmark of 2 HD 5870 and vs 2 HD 5850 the result was almost the same(FPS Wise) for a lot of games. maybe a 2-3% increase for the HD5870x2.

So I don't really botter if the 5870 turn itself to a 5850.

I'm not familiar with shaders, so loosing around 10% would it be really noticable? I can afford one more HD5870 but if I can save a few buck and just loose around 5-10% of performance, I don't mind.


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Graphics card Master

I'm not so sure the 5870 will "downclock" itself or disable shaders, I'd like to see some proof of that. The reason is, I have 5850s in CF and I can easily OC one card and not the other. For example, I did it by accident - I OCed one card to 850/1200 and the other was still at stock, but my FPS in a FurMark test went up quite a bit. Then I realised my mistake and OCed the 2nd card, and retested, and my score went up even more. So 2 cards can definitely run in CF at different speeds.

wolfram23 said:
I'm not so sure the 5870 will "downclock" itself or disable shaders, I'd like to see some proof of that. The reason is, I have 5850s in CF and I can easily OC one card and not the other. For example, I did it by accident - I OCed one card to 850/1200 and the other was still at stock, but my FPS in a FurMark test went up quite a bit. Then I realised my mistake and OCed the 2nd card, and retested, and my score went up even more. So 2 cards can definitely run in CF at different speeds.


I guess I could OC the 5850 easily no?

But damn i suck at Ocing, eveytime I'm trying to do so, my PC freeze..LOL.
Did you use the ATI overdrive panel to OC your 5850s? Or another software?
Graphics card Master

mike30 said:
I guess I could OC the 5850 easily no?

But damn i suck at Ocing, eveytime I'm trying to do so, my PC freeze..LOL.
Did you use the ATI overdrive panel to OC your 5850s? Or another software?

Use MSI afterburner, nifty program.

wolfram23 said:
^ yeah Afterburner... and then BIOS flashed :D 


Which I want to avoid at all cost... :) 

I think I'll go with the HD5850, even if my 5870 "downgrade" to the 5850, both in crossfire show extreme performance.
It's a good 120$ less expensive and for my needs on a 1920*1200 resolution this would be way sufficient

I read this review to help me in my choice.
http://www.legitreviews.com/article/1107/2/


and maybe try in the future to start OCing a bit :) 

Thx for all your input guys!

Quote:
Hybrid crossfire is not commonly and tested with games by online reviewers.so how a game will scale with such setup is also questionable.


Yeah, that's the reason why i'm confuse between one more HD5870 or a HD5850.

I think I changed my mind, since I can afford the HD5870, I'll go with it. I want to get the maximum I can with 2 HD5870 and avoid any problem

I think I'm good for a few years for an extra 120$ :) 
Graphics card Master

wolfram23 said:
I'm not so sure the 5870 will "downclock" itself or disable shaders, I'd like to see some proof of that. The reason is, I have 5850s in CF and I can easily OC one card and not the other. For example, I did it by accident - I OCed one card to 850/1200 and the other was still at stock, but my FPS in a FurMark test went up quite a bit. Then I realised my mistake and OCed the 2nd card, and retested, and my score went up even more. So 2 cards can definitely run in CF at different speeds.

I know that at least the memory speeds/sizes match each other. Here is a review of HD5870+HD5850 crossfire;
http://www.legitreviews.com/article/1107/1/
Shows the combination is actually slightly slower than 2 x HD5850.
Graphics card Master

Quote:
Hybrid crossfire is not commonly and tested with games by online reviewers.so how a game will scale with such setup is also questionable.

Hybrid crossfire is something different. It is what ATI called their crossfire between low end video cards and the IGP on their motherboards. The most common phrase for what we are talking about here is "mixed crossfire."
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