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Will this bottleneck 3 way Crossfire/SLI?

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June 19, 2009 7:34:04 PM

Hello, I am thinking about upgrading my 2 4870 X2s to 3 4890 Sapphire Toxic or Atomic edition cards and seeing just how far I can push past the 1Ghz range. My thought process is that @ somewhere inbetween 900-950 Mhz core the 4890 matches the GTX 285 and if these Sapphire versions with the better cooling, better capacitors, and higher voltage should be able to overclock well past what they are rated at and should be faster than a overclocked GTX 285 that is maxed out (790/1395 Mhz in my experience) making them the fastest single-card GPU out. :D 

My question is this:

I have an MSI Eclipse which I like very much. however like almost any other X58 motherboard out there it does 3 way Crossfire/SLI @ x16/x16/x4. I am wondering how much that x4 speed will bottleneck the third card?

My thought process is that the driver scaling and the lack of memory use of the 3rd card should make it so that the x4 bandwidth wont make a difference, but I want some other opinions too.
a b U Graphics card
June 19, 2009 7:47:01 PM

I wouldn't do that.. It would be a big cash sink for almost no gain.

Even in the best of cases it would only be marginally better anyway. But besides that if you really are that eager to spend money why not just get a new mb too?

In todays games you would be looking at a loss of 10-20% in the x4 slot IF it was the only card.. but I really am not sure how that would affect crossfire with 2 others as it will have to be sending and recieving data.. Given scalign it probably wont make a differnce.. but its still a waste of money :) 

I must ask though.. why bother? the cards you ahve now wil max everything well into the next generation.. invest the money and buy 5890 triple corssfire then.. Or you know.. spend it on something that would give you a bigger upgrade, like faster storage.
June 19, 2009 7:59:04 PM

I agree with the above. It would be a pointless upgrade without a new mobo.
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a c 235 U Graphics card
June 19, 2009 8:00:15 PM

i have to ask.....how are the dual 4870x2 not meeting your gaming expectations?

other then that, i agree with daedalus (save your money for a future date)
June 19, 2009 8:00:49 PM

I want to do this because I can sell my 4870 X2s to my cousin who is finally looking to upgrade from his crossfired 2900 XTX space heat... err graphics cards for $800 (including my waterblocks which each cost $200, its a good deal for him) which will make a net gain of $50 with the Toxic or a loss of $50 for the Atomic versions. Also I recently put a Sapphire 4890 Vapor which is 870 Mhz core/ 1050 Mhz core at stock and has the same improvements as the Atomic edition (better caps, higher voltage, though the cooling isn't as good). I was curious so I overclocked it on air to an amazing 1044 Mhz core/ 1168 Mhz memory! Though I noted load temps of about 95-96c, so the better cooler is a must.

Also The difference between those 4890s and my 4870 X2s should be the same or perhaps greater than the difference between 3 GTX 285s and 2 4870 X2s, which is not bad.

I can upgrade my board and sell my current one no problem. I just wonder if X16/X8/X8 will do any better or if I should try for a X16/X16/x8 board.
June 19, 2009 8:01:47 PM

ct1615 said:
i have to ask.....how are the dual 4870x2 not meeting your gaming expectations?

other then that, i agree with the above poster


They are and for that matter my first 4870 X2 was. This is more for the fun of overclocking and helping out my cousin.

Edit: Sorry I should have explained in my main post.
a b U Graphics card
June 19, 2009 8:08:44 PM

Well, assuming you are not scraping the 4870x2's for teh upgrade then it will probably increase performance.

Keep in mind I've never been able to OC my crossfired cards as high as the cards on their own go, for whatever reason.

I know the rough effect x4 has on a single card, but I really can't say how that plays out in crossfire. Even if it is a big hit I would have to assume the triple 4890's would work better than a couple 4870x2s (though not much).

Given that you can always test it and get a new mb later and tell us the results ;) .
June 19, 2009 8:13:59 PM

Very true, but I don't know anyone with an X58 that has 3 PCIe and supports anything other than X16/X16/X4.

I'm not really expecting much in the way of a performance gain, but I want to compare a maxed out Sapphire Toxic or Atomic 4890 with a maxed out XFX GTX 285 Alpha Dog to see which card is truly the king. :D 

I just thought of something. I'm going to look up GTX 275/GTX 285 reviews to see if they are using a similar motherboard.
June 19, 2009 8:23:41 PM

Form what I can see, X16/X16/X8 setups are all that the review sites use, so it looks like an upgrade for me... oh well.
a c 147 U Graphics card
June 19, 2009 9:38:25 PM

Multiple GPU configs are easily limited by the CPU.

Unless you have one of the very best current quad-core CPU's you will be limited by your CPU and all your extra graphics power is doing is adding heat.

I personally don't recommend going above two cards.
a c 235 U Graphics card
June 19, 2009 9:39:34 PM

if one 4870x2 was meeting your gaming expectations, sell the other one to your cousin and upgrade next year when directX11 cards out.
June 19, 2009 10:14:20 PM

@OP

If I were you I wouldn't upgrade my computer and instead use the money to go on a date and get laid. You need to stop obcessing over your computer " score ".
a c 235 U Graphics card
June 19, 2009 10:16:37 PM

Major_Spittle said:
@OP

If I were you I wouldn't upgrade my computer and instead use the money to go on a date and get laid. You need to stop obcessing over your computer " score ".


wow, so nice of you offering your "companionship" services
a c 147 U Graphics card
June 20, 2009 1:07:52 AM

Yeah, some of us are married and no longer care about women...
June 20, 2009 2:06:35 AM

photonboy said:
Multiple GPU configs are easily limited by the CPU.

Unless you have one of the very best current quad-core CPU's you will be limited by your CPU and all your extra graphics power is doing is adding heat.

I personally don't recommend going above two cards.


Yeah... X58 = LGA 1366 = Nehalem

Sig: i7 920 @ 4.2 Ghz

I'll be fine...
June 20, 2009 2:15:46 AM

Honestly I have already outlined that:

A) I will not lose any money in this transaction on a GPU level.

B) I enjoy overclocking and I want to see what this setup can do.

C) I will have plenty of cash come DX11 and besides my finances are not in question. I did not ask if it was worth it, only how well it will work on a theoretical level.

D) My dating and personal life are not up for debate, what my girlfriend and I do in our spare time is our business. Plus, correct me if I am wrong, but I'm pretty sure a suggestion like that can be taken as a proposition which, in light of my age, is illegal...

If it makes you feel better Spittle, it is my girlfriend's computer that is using the GTX 285 with an i7 920 @ 4.0 Ghz on air, which is the one I bought her.

Edit: I am supposed to mention she bought me a pair of full length stainless steal BBK headers for my Mustang around the same time.
June 20, 2009 8:50:27 PM

Sell the eclipse and purchase a eclipse plus or p6tws supercomputer so you can run all 3 cards at 16x. There really is not point in running 3 cards if you can not run at full 16x on all of them.
!