Crossfire at low resolutions

Hindesite

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So I recently got a 4870 IceQ 4+ and am loving it! The card runs very cool and I've actually been able to max the clock sliders in Catalyst Control Center to 790/1100 at just 40% manual fan speed, under 70degrees during heavy load! :ouch:

I chose this card even though I wanted a 4890 for heat concerns. I've had many friends with decent cases who've had heat issues with just their 4870s using stock coolers, some of which were forced to buy aftermarket VGA coolers just to quell their graphics issues. I did my research and found that the IceQ line of Radeon cards from HIS was one of the highest rated cards with a special cooler built-in. HIS didn't offer a 4890 with the IceQ cooler from what I could find, so I decided the slower clocked 4870 with an IceQ cooler was for me. :)

I'm happy with my choice, but I still want a little more power. When pushing heavy AA/AF on some games I've seen the FPS dip below 30 average, which is a little too noticeable for me. Because it pertains to the situation, here's the rest of my rig:

Corsair 750w PSU (4 PCIE connectors)
ASUS M3A79-T Deluxe (supports crossfire)
Phenom 9950 2.6Ghz
8GB DDR2 1066

So my question is how much will crossfire improve my performance? Will my CPU bottleneck it? I haven't done heavy research on it, but it appears crossfire really helps most with high resolution displays. My 22" monitor only supports 1680x1050. Does my low resolution make crossfire a less desirable choice for me?


Thanks for the help, guys. :)
 

daedalus685

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Crossfire has limited scaling at lower resolutions. You will not get as much bang for another 4870 as you would at a higher resolution. You should expect 50% or so in most games at that resolution.. some more, some less. 80% or more is normal for higher resolutions.
 

Hindesite

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Well then in response to that, what gives higher performance gains: A single Radeon HD 4870 X2 or two Radeon HD 4870s in a crossfire? Or is it basically the same thing? Also, would the power requirements for both of those be similar or does 2 seperate 4870s in a crossfire have higher PSU requirements?

Two of the card I bought totals just a little cheaper then a Radeon HD 4870 X2.
 

xaira

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2 4870x2 in crossfire have less power supply requirement than 4 4890s, 2 4870x2 will give you more performance than 1 4870x2 but the difference in fps between 3 4890 and 4 4890 is really small because scaling beyond 3 cards becomes iffy
 

Hindesite

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Thanks, but my question was for ONE 4870 X2 vs TWO 4870's. No 4890's, I didn't get one of those. I just want to know if I get a second 4870 how it will compare to if I just got one 4870 X2 in the first place, in regards to performance and power requirements, since I know a 750W doesn't give a lot of breathing room for a 4870 X2 or two 4870's in a crossfire. :)
 

Hindesite

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So if the 4870's have 1GB each then they're basically the same as a 4870 X2 2GB? I figured as much but I thought I'd still ask. Thanks! :)
 

pauldh

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What games do you play? In games such as Crysis, Stalker Clear Sky, and Supreme Commander, one HD 4870 will not be sufficient for maximum details (esp. w/ FSAA). So, in these GPU limited situations, yes a second HD 4870 would make a big difference even at 1280x1024.

Will your CPU hold them back...(depending on the game)...Yes it sure will.

http://www.tomshardware.com/reviews/amd-cpu-overclock,2304-7.html
Take a look at the 4 games in this article. It contains your CPU and 3 others, stock and overclocked, and paired with an HD 4870 and HD4870X2. Only the four games from our 32-bit SBM test suite though. But you'll see your CPU is actually already holding back a single 4870 is CPU intensive games like World In Conflict. But look at the HD 4870X2 results and you see just how much it can hold back 2 * 4870 GPU's. A CPU OC does help, but still won't make it a Phenom II class.

 

Hindesite

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I've never done a serious CPU overclock but I already have a pretty beefy cooler because I knew I eventually would when I got the Black Edition. You got a guide I could use to make it easier for an overclocking newbie? :)