CrossFire X explored

[JPB]

Techreport Link

Cards tested
___________

GeForce 8800 GT
GeForce 8800 GTS
GeForce 8800 GTS 512
GeForce 8800 GTX
GeForce 8800 Ultra
GeForce 8800 Ultra SLI (x2)
GeForce 8800 Ultra SLI (x3)
Radeon HD 2900 XT
Radeon HD 3850
Radeon HD 3870
Radeon HD 3870 X2
Radeon HD 3870 X2 + 3870 (x3)
Radeon HD 3870 X2 CrossFire (x4)

 

[n7]

Yeah, great review :thumbsup:

I checked it out the other day.

Lots of 2560x1600 tested

 

[BFG10K]

Look at this gem from page 2:

(Gotwalt said Microsoft built this limitation into the OS, interestingly enough, because "a certain graphics vendor?not us" was queuing up many more frames than the apps were accounting for, leading to serious mouse lag. Game developers were complaining, so Microsoft built in a limit.)

Ah yes, more evidence of SLI mouse lag, like I?ve been saying for months.

 

[n7]

Haha, i actually thought of you when i was reading that part

Doesn't surprise me really.

I just don't see how even the most impeccably tweaked multi GPU setup can ever be truely excellent though the more i understand it.

There are just to many limitation & drawbacks that i cannot see ever disappearing...
I hope i'm wrong though...or i hope we see a quick end to this high end being multi-GPU nonsense.

Of course, likely neither of my wishes will come true.

 

[Sylvanas]

That was a good read, what I found most interesting was his interview with Dave Gotwalt, particularly this:

In this context, I asked about the opportunities for multithreading the driver in order to take advantage of multiple CPU cores. Surprisingly, Gotwalt said that although AMD's DirectX 9 driver is multithreaded, its DX10 driver is not?neither for a single GPU nor for multiples. Gotwalt explained that multithreading the driver isn't possible in DX10 because the driver must make callbacks though the DX10 runtime to the OS kernel, and those calls must be made through the main thread. Microsoft, he said, apparently felt most DX10 applications would be multithreaded, and they didn't want to create another thread. (What we're finding now, however, noted Gotwalt, is that applications aren't as multithreaded as Microsoft had anticipated.)

I would have thought M$ could have realized this drawback and implemented it in DX10.1....that would be pretty useful I'd imagine- however i guess DX10.1 was finalized before DX10 really came to the market.

It does show however how much work AMD are putting into the drivers, and the scaling is pretty good with 3 GPU's (limited with four due to the three-frame render ahead limit I'd assume?). Where I am in the world, 3 Ultra's cost at least 2.5 times more than an X2 + 3870 and are twice as power hungry so goes to show Tri-SLI is a joke with the G80.

Also it makes you think if Crytek are to blame for an utterly terrible scalable engine with Cryengine 2...improvements will come in time however I'd bet not to much avail.

 

[JPB]

I am going to be building a new rig soon. And after reading this review, I think I made up my mind.

But I would like some opinions on it.

The *monitor* that will be used is a 40" Samsung LCD TV.....1080p. Maximum resolution is 1920x1080.

Do you all think if I went with a 3870X2 + a 3870 it would be fine for this setup ?

And as far as games I play, well.......you can forget about Crysis. I just simply do not like the game. It would be more along the lines of COD4, Oblivion, Prey, Stalker.

Opinions ?

 

[heyheybooboo]

Originally posted by: JPB
I am going to be building a new rig soon. And after reading this review, I think I made up my mind.

But I would like some opinions on it.

The *monitor* that will be used is a 40" Samsung LCD TV.....1080p. Maximum resolution is 1920x1080.

Do you all think if I went with a 3870X2 + a 3870 it would be fine for this setup ?

And as far as games I play, well.......you can forget about Crysis. I just simply do not like the game. It would be more along the lines of COD4, Oblivion, Prey, Stalker.

Opinions ?

If your are going to jump into serious multi-gpu it looks like 3 x HD 3850s (maybe with a nice little OC tweak) would be the ticket around $500.

Your issues I think will center around specific game optimizations for 1920x1080. That's a 16:9 aspect ratio. Games are generally optimized for 16:10.

It will run fine in 16:9. It will run better in 16:10.

 

[Edgar Allan Pwnage]

Hey guys, I was thinking about doing a crossfire-3x setup and wanted to ask if there was any difference in regards to which slot you would put the video cards in. For example, I was looking to use a 3870 Oc'd to 850mhz in the 1st slot and a 3870x2 in the 2nd slot. Would this kind of setup give me the benefits of the premium oc'd single 3870 while reducing the power consumption and heat of the 3870x2? etc. Does it matter which card is closest to the cpu? Thanks.

 

[Sylvanas]

Originally posted by: Edgar Allan Pwnage
Hey guys, I was thinking about doing a crossfire-3x setup and wanted to ask if there was any difference in regards to which slot you would put the video cards in. For example, I was looking to use a 3870 Oc'd to 850mhz in the 1st slot and a 3870x2 in the 2nd slot. Would this kind of setup give me the benefits of the premium oc'd single 3870 while reducing the power consumption and heat of the 3870x2? etc. Does it matter which card is closest to the cpu? Thanks.

What motherboard do you plan on using with this setup? With a 16 x 4 setup on most Intel chipsets excluding the X38/X48, you'd want the X2 in the Primary PCI-E 16x slot (closest to the CPU) as you'd most certainly not want the dual GPU card to be bandwidth starved- so that leaves the single 3870 in the 4x slot. Note that having the single 3870 in a 4x slot will not effect the OC on the core that you mentioned. If however you are using an RD790/ X38/X48 board it will not matter which PCI-E slot you position the cards in as both will recieve dual 16x PCI-E 2.0. If you're board comes with 3 and 4 slots, be sure to make sure you use the native 16x slots....your motherboard manual will tell you about this as most manuals have a page on dual GPU operation.

 

[VERTIGGO]

Originally posted by: Edgar Allan Pwnage
Hey guys, I was thinking about doing a crossfire-3x setup and wanted to ask if there was any difference in regards to which slot you would put the video cards in. For example, I was looking to use a 3870 Oc'd to 850mhz in the 1st slot and a 3870x2 in the 2nd slot. Would this kind of setup give me the benefits of the premium oc'd single 3870 while reducing the power consumption and heat of the 3870x2? etc. Does it matter which card is closest to the cpu? Thanks.

My CCC doesn't show any overclock options. I'm pretty sure you can't overclock one card without the others as well. Like they said a 3870 automatically clocks back to stay in step with a 3850.

I've been testing in XP and I get a 30% increase having two 3870X2s installed with CFX and AI on. This is confusing since it's only supposed to work in Vista. This is only at 2560x1600 without AA. At other settings, a single card performs almost exactly the same as having 2 in when CFX is on. When it's turned off, I'm pretty sure it just disables Crossfire altogether so I'm running one RV670 and 3 are shut off. I'll have to test in Vista as well.

 

[VERTIGGO]

BLUE - blue PCI-E slot
3870X2X2 - two boards with bridge


Opposing Fronts max @ 2560x1600 4xAA/16xAF

3870X2 BLUE 38.1 CFX ON AI ON
3870X2X2 38.0 CFX ON AI ON
3870X2X2 35.1 CFX OFF AI ON

Opposing Fronts max @ 2560x1600 0xAA/16xAF

3870X2X2 75.0 CFX ON AI ON
3870X2X2 74.7 CFX ON AI ADV
3870X2 BLUE 51.5 CFX ON AI ON
3870X2X2 47.1 CFX ON AI OFF
3870X2 BLUE 46.2 CFX OFF AI ON
3870X2 BLUE 44.5 CFX OFF AI OFF
3870X2X2 43.4 CFX OFF
3870X2 BLACK 39.8 CFX- AI ON


Opposing Fronts max @ 1920x1200 4xAA/16xAF

3870X2 BLUE 98.5 CFX ON AI ON
3870X2X2 91.5 CFX ON AI ON
3870X2X2 57.1 CFX OFF AI ON

Opposing Fronts @ 1920x1200 0xAA/16xAF

3870X2X2 99.1 CFX ON AI ON
3870X2X2 75.6 CFX OFF AI ON

Opposing Fronts MIN @ 800x600 0xAA/0xAF

3870X2X2 329.4 CFX ON AI ON
3870X2X2 294.9 CFX ON AI ON (PHYSICS ON HIGH)

 

[Sylvanas]

Originally posted by: VERTIGGO

Originally posted by: Edgar Allan Pwnage
Hey guys, I was thinking about doing a crossfire-3x setup and wanted to ask if there was any difference in regards to which slot you would put the video cards in. For example, I was looking to use a 3870 Oc'd to 850mhz in the 1st slot and a 3870x2 in the 2nd slot. Would this kind of setup give me the benefits of the premium oc'd single 3870 while reducing the power consumption and heat of the 3870x2? etc. Does it matter which card is closest to the cpu? Thanks.

My CCC doesn't show any overclock options. I'm pretty sure you can't overclock one card without the others as well. Like they said a 3870 automatically clocks back to stay in step with a 3850.

I've been testing in XP and I get a 30% increase having two 3870X2s installed with CFX and AI on. This is confusing since it's only supposed to work in Vista. This is only at 2560x1600 without AA. At other settings, a single card performs almost exactly the same as having 2 in when CFX is on. When it's turned off, I'm pretty sure it just disables Crossfire altogether so I'm running one RV670 and 3 are shut off. I'll have to test in Vista as well.

A 3870 does not 'clock back' to stay in step with a lower clocked card. As of the 8.1 drivers you can have any number of 38xx series cards all running individual clocks, it is only when you have two differing frame buffers that the lower of the two is used. Also CCC has OC options via the use of 'Overdrive' to which if you have a card that has an 8pin PCI-E connector like a 2900 or 3870X2 you need to use that 8pin connector in order to access Overdrive.....not just two 6pin connectors.

 

[apoppin]

Originally posted by: Sylvanas

Originally posted by: VERTIGGO

Originally posted by: Edgar Allan Pwnage
Hey guys, I was thinking about doing a crossfire-3x setup and wanted to ask if there was any difference in regards to which slot you would put the video cards in. For example, I was looking to use a 3870 Oc'd to 850mhz in the 1st slot and a 3870x2 in the 2nd slot. Would this kind of setup give me the benefits of the premium oc'd single 3870 while reducing the power consumption and heat of the 3870x2? etc. Does it matter which card is closest to the cpu? Thanks.

My CCC doesn't show any overclock options. I'm pretty sure you can't overclock one card without the others as well. Like they said a 3870 automatically clocks back to stay in step with a 3850.

I've been testing in XP and I get a 30% increase having two 3870X2s installed with CFX and AI on. This is confusing since it's only supposed to work in Vista. This is only at 2560x1600 without AA. At other settings, a single card performs almost exactly the same as having 2 in when CFX is on. When it's turned off, I'm pretty sure it just disables Crossfire altogether so I'm running one RV670 and 3 are shut off. I'll have to test in Vista as well.

A 3870 does not 'clock back' to stay in step with a lower clocked card. As of the 8.1 drivers you can have any number of 38xx series cards all running individual clocks, it is only when you have two differing frame buffers that the lower of the two is used. Also CCC has OC options via the use of 'Overdrive' to which if you have a card that has an 8pin PCI-E connector like a 2900 or 3870X2 you need to use that 8pin connector in order to access Overdrive.....not just two 6pin connectors.

actually 2-6 pin connectors will work if you are willing to "mickey mouse" the other two pins with two alligator clips and wire.

This discusses my experience with my own FrankenFire and details how to "fool" CCC [i won't be O/C'ing at all when i get 3870x2 + 2900xt]

Crossfire Woes

 

[VERTIGGO]

you can run 3870X2 + 2900XT? how does that work? I would use that config until 3870X2 x2 is feasible

 

[apoppin]

Originally posted by: VERTIGGO
you can run 3870X2 + 2900XT? how does that work? I would use that config until 3870X2 x2 is feasible

it is not "official" ... but there was another site that easily got it to work with Cat 8.2 [i think] and it worked fairly well performance-wise from what little they posted about it.
.. it might be in my "Crossfire Woes" thread i linked in the post above yours. If not, it is in my archived bookmarks and i have to look if you want me to find it.

and you are getting a little ahead of me ... "3870x2 + 3870x2" - true Quad - QuadCrossfireX IS feasible [for me - i won't even have to change my PS] and it might even be my next - next - upgrade if 3870x2 is "dirt cheap" by then. Of course, even with by e4300@3.5Ghz it may be a little bottleneck .. so that would finally force me to drop a QuadCore CPU in.

.. and IF i continue on this multi-GPU route, it looks like Skulltrail becomes the best MB option for me .. and it looks a little pricey ..
-no wonder NewEgg CS seems so extra nice to me

 

[VERTIGGO]

by feasible I mean worth having. I use XP and therefore the second card essentially does nothing. That's what I was pointing out in my benchmarking^