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4870 x2 or 6850

post #1 of 12
Thread Starter 
i recently posted a wanted add on craigslist for either a 6xxx series card or a 5870 and someone emailed me offering a pair of 4870 for 100, well i know this is a good deal but i have two questions

1. my MOBO says it supports crossfire but under the description it says 1x PCI Express x16 slots, running at x16 (PCIEX16_1) (Note 2)
1 x PCI Express x16 slots, running at x8 (PCIEX8_1) (Note 2)
(The PCIEX16_1 and PCIEX8_1 slots support ATI CrossFireX technology, and conform to PCI Express 2.0 standard.)

will the one running at x8 slow down the card or what exactly does it mean?

how will the performance of a crossfire 4870 compare to that of a single 6850, am i better off to continue saving for a 6850?
post #2 of 12
PCIe x8 won't bottleneck a 4870.


2x 4870 - Faster in most games, cheaper, hotter, louder, more power consumption
6850 - Faster in non-Crossfire optimized games, expensive, cool, quiet, sips power


As you can see, I chose a second 4870 (paid $75 for it with all accessories included).


Also, see if you can work out a way to verify the cards work without the guy leaving your sight, so if he's scamming you you can shove them up his... exhaust pipe.
post #3 of 12
x8 slot shares bandwith with the x16 slot, so when you CF, the x16 will actually perform as x8. However, the performance will not be significantly impacted. Expect ~-4% from each slot.

About the second question - it depends whether DX11, power consumption and heat is important to you. Sure, HD 4870 CF will perform better, but HD 6850 is cooler, consumes significantly less power, and a great performer overall for today.

I would get the HD 6850 if I were you.

Cheers
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post #4 of 12
CF 4870 is more powerful than a 6850.
The difference between x16 and x8 is barely anything if your resolution is 1920x1200 or lower. Usually only 2-3 fps.

However, you won't have Direct X 11 which makes some games like Metro 2033 look amazing, but 2 HD 4870's for $100 is a steal!
    
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post #5 of 12
If your PSU supports them, I'd run 2 4870's any day. You'll be able to run much higher resolutions, AA, etc. And DX10.1 vs DX11 isn't a big deal really. Only a couple games are DX11 and its barely any visible increase in visual quality IMO.
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post #6 of 12
Thread Starter 
after rereading the email i think they meant a 4870x2, not a crossfire pair, should i still go for it, after googling they go for about 650 online makes me think this seems a bit too good to be true
post #7 of 12
Quote:
Originally Posted by luckypunk View Post
after rereading the email i think they meant a 4870x2, not a crossfire pair, should i still go for it, after googling they go for about 650 online makes me think this seems a bit too good to be true
Nothing's suspiscious here, HD 4870 X2 is quite an old GPU, and because of the AMD cards and new Fermi cards, this card's price went down.

HD 4870X2 is a powerful GPU, but it's quite old for today, and I think you should get a new AMD card (R6850).
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post #8 of 12
The HD4870x2 2GB is the 10th most powerful card available. Old don't mean it's slow.
post #9 of 12
Have I suggested that 4870x2 is slow?
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post #10 of 12
Thread Starter 
hmm after watching a few review vids i dont know if it will even fit in my case
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