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Will a 9950 drive two 4850's in crossfire?

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October 14, 2008 6:35:28 AM

I have searched the forums for days so forgive me if the answer is easily found here or elsewhere. I'm wondering if an AMD 9950 quadcore will prove a significant performance hit, ~10% or more, when paired with two HD 4850's in crossfire. If so, will overclocking it to 3 ghz or so overcome that bottleneck. Thanks for any help you can give. Please provide links to substantiating reviews if at all possible.
October 14, 2008 5:54:09 PM

It should be fine.

But on a side note I wish people would use a little common sense when asking this question. I see alot of "will my e8400 bottleneck my 4870?" stupidity.

Any modern CPU around 2ghz will have no issue with bottlenecking a single GPU. Ive ran an 8800 GTX on a E6300 running at anywhere from 1.86 ghz to 3.2ghz with no issues or really large gains because I over clocked my CPU speed.

However an SLI/Xfire setup will require a little more power. A 2.5ghz CPU is in order here, with myself leaning more toward at least a 3ghz dual core. I am currently running a pair of 4850s on an e8400 @ 3ghz. This cpu will probably see around 4ghz at some point, but I doubt if I will see a huge increase in FPS because I picked up 1 ghz on an overclock.

If you plan on running a pair of 4870X2s in Xfire or 280s in Tri-SLI you better figgure on at least a 3.5ghz+ CPU, and probably a quad core wouldnt be a bad idea. This may be my next setup, with a pair of 4870X2s paired up to a Q9650 @ 4ghz unless the new AMD cpus pull an elephant out of a hat. Kind of leaving my options open for this one.
October 14, 2008 6:22:05 PM

There aren't many reviews out there with Phenom's and gaming performance. However, the 9750/9850/9950 are all comparable to the Intel Q6600 in int/float performance. The 9850 is about the same speed, whereas the 9750 performs a couple percent lower and the 9950 performs a couple percent higher. Due to architectural differences, there are points where AMD has the upper hand, and points where Intel has the upper hand. The Q6600 tends to overclock a bit higher, with quite a few people pushing 3.4-3.6 ghz, while the Phenom series tend to hit their limit at around 3.4-3.5 on good air cooling and a 750 southbridge board (important). The 9xxx series has an appreciable amount more memory bandwidth than Intel's best (until i7 that is), but that is more geared to server and virtualization performance. People could argue days on the merits of each architecture, but for all intents and purposes they have similar performance.

There was a thread not too long ago that compared the performance of AMD and Intel chips, titled "Phenom as good or better than Intel at gaming?" or something on that order, that provided links to some relatively high resolution high-power benchmarks. While a lot of people poo-poo'd the idea, it illustrated the fact that on high resolutions, the game is more GPU bottlenecked than CPU bottlenecked. Really, if you have a decent quad (and 9750-9950 are decent quads), just clock it up to 3.0ghz and you should be able to run whatever high end graphics card combo you want, and it should perform well.

There are exceptions, as always, as not all games are made the same. Microsoft's FSX is far more CPU intensive than it is graphically. For that game, you would want as many cores as you can get... and as fast as you can get them. For that particular game/sim, Intel's core i7 will probably be the best option to have. But, for most games (which are predominantly single or dual threaded), a single dual core is sufficient. A decent quad would allow for a little bit of future-proofing though, as we are starting to see more and more 2-3+ thread games.

The only real variation in CPU speeds comes into play at the minimum FPS level, or at very low resolutions. If your game starts chopping at certain points, but remains smooth in others, and changing resolutions does not help, it's probably either time to overclock your CPU or buy another one (although low RAM resulting in heavy disk usage can do the same thing).

But, to answer your question, yes... the 9950 AMD will most likely be sufficient to run your games at 3.0 ghz.
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October 14, 2008 6:44:37 PM

Not exactly the same thing, but here is an article looking at CPU performance with a 4870X2:

http://www.legionhardware.com/document.php?id=770

Considering 4850CF is a bit slower than a 4870X2, I'd say a 9950BE overclocked to 3GHz+ (should be easy with a SB750 mobo) would be a good match and shouldn't be a big bottleneck.
October 14, 2008 8:08:41 PM

Thanks Everyone. Exactly the kind of input I was looking for and it's about the response I expected given the reviews I've seen. Thanks for the link Epsilon84. I've seen that review before and I kind of saw the 9950 as a bottleneck compared to even an intel e8400 overclocked, but I wasn't sure if the same will hold true for a lesser graphics setup (two 4850's vs 4870x2). Thanks a lot everyone, you've helped put my mind at ease.
October 14, 2008 8:51:36 PM

Try with 1 card in and with 2 cards and let us know how much more performance 2 cards gives you. Of particular note is the min fps, if this doesn't increase, two cards isn't helping there over one.

I personally find two hd4850s overkill and I would want alot more than 3GHz for even one card to keep the fps up and the bottlenecks down.
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