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quad crossfire: physically practical?

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December 11, 2007 9:47:31 PM

Well I'm new, and haven't been able to find anything regarding this very obvious problem that will likely face enthusiasts once the quad- drivers come round, so here it is:

With four HD3870's, they collectively take up 8 case expansion slots, whereas the vast majority of ATX cases contain only 7; :heink: 
Motherboards with four PCI 2.0 slots don't all spread them out enough for four double-slot cards, and
When you have four double-cards eating up all of the space in your case, where does cooling air come/go :sweat:  and where the heck are you supposed to put a sound card or networking card? :pfff: 

On an unrelated note, why has have the Tom's VGA charts completely omitted the HD 2900 XT 1GB DDR4? Surely this would put an ATi player a little higher on the charts. I emailed 'em, and got no response. :non: 
December 11, 2007 10:28:57 PM

waffle911 said:
Well I'm new, and haven't been able to find anything regarding this very obvious problem that will likely face enthusiasts once the quad- drivers come round, so here it is:

With four HD3870's, they collectively take up 8 case expansion slots, whereas the vast majority of ATX cases contain only 7; :heink: 
Motherboards with four PCI 2.0 slots don't all spread them out enough for four double-slot cards, and
When you have four double-cards eating up all of the space in your case, where does cooling air come/go :sweat:  and where the heck are you supposed to put a sound card or networking card? :pfff: 

On an unrelated note, why has have the Tom's VGA charts completely omitted the HD 2900 XT 1GB DDR4? Surely this would put an ATi player a little higher on the charts. I emailed 'em, and got no response. :non: 


ATI has yet to unveil tri-crossfire drivers for the few X38 chipsets that support 3 PCI-E slots, so I wouldn't hold my breath for the quads, it will likely be a little while. When people refer to quad-crossfire, they are referring to the supposedly upcoming X2 variants of current ATI GPU's, that is, dual gpu's on one PCB. Putting four seperate cards in would be somewhat ridiculous, as would trying to provide power to all of them, you'd need a workstation type board and a >1KW PSU. As for why the HD2900XT 1GB isn't on the charts, who knows? It's obsolete anyway, the 3870 spanks it pretty convincingly while using far less power and creating far less heat. So the overall position wouldn't change much at all for ATI.
December 11, 2007 10:40:09 PM

well yes it is but it's gonna be expensive so i wouldnt think about it, yet.
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December 11, 2007 11:04:09 PM

The issue is not simply drivers.
Drivers is only one factor.

The games also need to be written to properly support the extra cards.
It will be much like the issue with Single vs Dual vs Quad Core CPUs and various software.

I read a few articles on the topic, but I did not book mark them.

Basically, until very recently, few games were optimized for dual graphic cards (SLI). To add more graphic cards, the games will need to be optimized. In theory, the similar issues will exist for dual GPUs on a single PCB.

However, a Single Dual-Core GPU will have less issues due to the already SLI/CF ready nature of some games.

It will be the SLI/CF setup of Dual-Core GPUs that will be real tricky.
I'm sure this will come at some point, but expecting 3/4 Graphics Cards all with Multiple Cores to function is something that I think is quite a ways off.

I actually expect to see more of the GPU work to start off-loading back to the CPU since this there will be excess processing power there already since most games only use two cores and are not CPU bound.
This leaves two cores completely unused and free for use.

I know Intel has had some irons in the fire to help make more use of the CPU for Graphics as they move to 4-way and soon 8-way processors.



December 12, 2007 8:11:40 PM

zenmaster said:
The issue is not simply drivers.
Drivers is only one factor.

The games also need to be written to properly support the extra cards.
It will be much like the issue with Single vs Dual vs Quad Core CPUs and various software.

I read a few articles on the topic, but I did not book mark them.

Basically, until very recently, few games were optimized for dual graphic cards (SLI). To add more graphic cards, the games will need to be optimized. In theory, the similar issues will exist for dual GPUs on a single PCB.

However, a Single Dual-Core GPU will have less issues due to the already SLI/CF ready nature of some games.

It will be the SLI/CF setup of Dual-Core GPUs that will be real tricky.
I'm sure this will come at some point, but expecting 3/4 Graphics Cards all with Multiple Cores to function is something that I think is quite a ways off.

I actually expect to see more of the GPU work to start off-loading back to the CPU since this there will be excess processing power there already since most games only use two cores and are not CPU bound.
This leaves two cores completely unused and free for use.

I know Intel has had some irons in the fire to help make more use of the CPU for Graphics as they move to 4-way and soon 8-way processors.


The usefulness of CPU cores for additional graphics processing is, well, limited at best. GPU's are massively parallel, whereas a modern CPU is not. Therefore it would seem there would be some hurdles to overcome from a coding standpoint to use a CPU core as a aux GPU.

Let's not forget another important reason why tri/quad crossfire might not be the cat's meow: overhead. Remember Nvidia's abortive attempt to implement quad-sli? When you're trying to prioritize between 3 or 4 devices, you rack up an immense amount of overhead that drivers have to be able to overcome smoothly. Nvidia failed rather miserably in this department, and although ATI typically has better drivers, I can forsee them having many of the same type of problems if they try to go this route. The CPU might just have to be utilized to coordiate GPU-bound traffic efficiently.
a c 130 U Graphics card
December 12, 2007 8:27:23 PM


cb62fcni Wrote
The usefulness of CPU cores for additional graphics processing is, well, limited at best. GPU's are massively parallel, whereas a modern CPU is not. Therefore it would seem there would be some hurdles to overcome from a coding standpoint to use a CPU core as a aux GPU.

Can i just ask, Isnt this the whole point of the fusion and nehalem(prob spelt that wrong but) cores to enable some on chip graphics capabilities ?
Sure it wont be much to start with but from what i can find on the net and other places Intel seem quite pleased with what they have seen of th etc so far.
Mactronix
December 13, 2007 12:47:13 AM

mactronix said:
cb62fcni Wrote
The usefulness of CPU cores for additional graphics processing is, well, limited at best. GPU's are massively parallel, whereas a modern CPU is not. Therefore it would seem there would be some hurdles to overcome from a coding standpoint to use a CPU core as a aux GPU.

Can i just ask, Isnt this the whole point of the fusion and nehalem(prob spelt that wrong but) cores to enable some on chip graphics capabilities ?
Sure it wont be much to start with but from what i can find on the net and other places Intel seem quite pleased with what they have seen of th etc so far.
Mactronix


Yep, Fusion and Nehalem both offer GPU capabilities on-die, but it's important to remember that the GPU functions for both of them are added-in, that is, they don't share the same architecture with the CPU cores that are in the same die. This is for the same reason I mentioned earlier; GPU and CPU architecture is dramatically different.

And KyleSTL, I have no idea what that case is, my guess would be some type of server/workstation type case. Maybe they even had it custom built. Regardless, 2 3870X2's makes a whole load more sense for a quad setup than 4 independant cards. We'll just have to wait and see what ATI provides, and then whether software support develops.
a b U Graphics card
December 13, 2007 2:23:42 AM

I cant remember where I read it, but doing fusion/larrabee, theyll need to raise the parralism of the multi-cpu if I remember correctly, to the point where its closer to the gpu, thereby giving more graphics power, without completely undoing the 86 arch. It was way over my head, and I also remember this was tried before in the past, but was given up, mainly because the cpu's of the day didnt have near the processing power of todays chips, nor the advanced micro code. Its coming, and someday our discreet will be a cpu/gpu combo, and an upgrade will only be determined by speeds/ipc/quad-octo. Oh, and drivers heheh
December 13, 2007 11:56:02 AM

Lord ... I think I'd wait for the dual cores .... then you'd only need 2 !
December 13, 2007 12:27:59 PM

Wasn't this the point behind AMD acquiring ATI? The big question now is whether AMD has the resources to do the R&D to make it happen.

Regarding 4 cards and the space in a case. No special case is required. The person that would want that setup would first have to buy a board designed for it and the sound would probably be a great chip with standard net card on board. (also, if they can afford the board and the cards they could afford a 'special'case.) This woud be a niche product. ASUS has 4 PCI-E slot boards out now and has had them available for a couple of years. I own one with 4 video cards in it for my day-trading work-a niche market.
a c 143 U Graphics card
December 13, 2007 1:26:51 PM

Why 4 video cards, are you using 8 monitors in your work??? :o 
December 13, 2007 1:28:32 PM

waffle911 said:
Well I'm new, and haven't been able to find anything regarding this very obvious problem that will likely face enthusiasts once the quad- drivers come round, so here it is:

With four HD3870's, they collectively take up 8 case expansion slots, whereas the vast majority of ATX cases contain only 7; :heink: 
Motherboards with four PCI 2.0 slots don't all spread them out enough for four double-slot cards, and
When you have four double-cards eating up all of the space in your case, where does cooling air come/go :sweat:  and where the heck are you supposed to put a sound card or networking card? :pfff: 

On an unrelated note, why has have the Tom's VGA charts completely omitted the HD 2900 XT 1GB DDR4? Surely this would put an ATi player a little higher on the charts. I emailed 'em, and got no response. :non: 

on board network over the pci-e bus.

PCI network cards will just be slowed down by the pci sound card, and other on board pci stuff like firewire.
December 13, 2007 3:02:51 PM

3 scale well at high res, nvidia anyway.


I think ATI does it differently IDK about that though I like nvidia. Its probably how ATI cards scale so much better thean nvidia ones.
December 13, 2007 3:20:32 PM

zenmaster said:
The issue is not simply drivers.
Drivers is only one factor.

The games also need to be written to properly support the extra cards.
It will be much like the issue with Single vs Dual vs Quad Core CPUs and various software.

I read a few articles on the topic, but I did not book mark them.

Basically, until very recently, few games were optimized for dual graphic cards (SLI). To add more graphic cards, the games will need to be optimized. In theory, the similar issues will exist for dual GPUs on a single PCB.

However, a Single Dual-Core GPU will have less issues due to the already SLI/CF ready nature of some games.

It will be the SLI/CF setup of Dual-Core GPUs that will be real tricky.
I'm sure this will come at some point, but expecting 3/4 Graphics Cards all with Multiple Cores to function is something that I think is quite a ways off.

I actually expect to see more of the GPU work to start off-loading back to the CPU since this there will be excess processing power there already since most games only use two cores and are not CPU bound.
This leaves two cores completely unused and free for use.

I know Intel has had some irons in the fire to help make more use of the CPU for Graphics as they move to 4-way and soon 8-way processors.


Your bang on the money there! When I first got into PCs, back around winter 2004, the nvidia 6 series and ati x800s were the hot new things. Back then multi-card setups were a new and promising idea, but its taken until very recently before they have had widespread support in games. A magazine in here in the u.k called 'custom pc' did a feature on a quad-sli setup (2 x nvidia gx2s) and it was basically a storm in a teacup for seemingly everything except f.e.a.r, which at the time (pre nvidia 8800 series) ran insanely well with those cards.

But I think quad crossfire is going to be implemented in a different way to the nvidia quad-sli setup as they will try and get each card to render alternate frames independent of each other. So that say with 4 gpus each one will render a frame, then wait for the other 3 to do their frames, then render the next, like a 1,2,3,4,1,2,3,4 and so on kind of system. As far as i can remember from that article they (the magazine) were saying that in quad-sli the gpus worked in a chain type fashion, collectively working on rendering the same frames together, not on their own rendering seperate ones. If anyone has this issue from about late 2006 I think, or has any info to clarify, please feel free!

Driver issues and game support will likely be a headache, but ati are taking their time on writing the drivers so at least their not rushing it out in a half-assed hurry, ala phenom style.

December 13, 2007 3:50:30 PM

hcforde said:
Regarding 4 cards and the space in a case. No special case is required. The person that would want that setup would first have to buy a board designed for it and the sound would probably be a great chip with standard net card on board. (also, if they can afford the board and the cards they could afford a 'special'case.) This woud be a niche product. ASUS has 4 PCI-E slot boards out now and has had them available for a couple of years. I own one with 4 video cards in it for my day-trading work-a niche market.


No, you would need a special case as the 4 cards being discussed are each dual-slot and the reference ATX case has 7 expansion slots. If someone was trying to quad-sli 8800GT's it wouldn't be as big a deal as they are single-slot designs.
December 13, 2007 4:15:23 PM

cb62fcni said:
No, you would need a special case as the 4 cards being discussed are each dual-slot and the reference ATX case has 7 expansion slots. If someone was trying to quad-sli 8800GT's it wouldn't be as big a deal as they are single-slot designs.

Yeah, but how the heck are you going to exhaust 360W out of the case (for the GPUs alone)?
Your case would need to look like this:

or this:

:kaola: 
December 13, 2007 5:10:57 PM

oooooooh the bottom one with the blue roof of fans looks nice
December 13, 2007 5:41:52 PM

It's a $600 pre-water-cooled configuration of a Lian Li 343B case on Performance-pcs.com I think frozen CPU has a mod'ed one too for $1000.
December 13, 2007 6:27:19 PM

There are cases that can do it.


But I think the general thing to do is WC them, if you are using 4.


Besides, 3 is still possible too, only one bvoard can do 4way with dual slot atm anyway and thats the MSI one, the others havent got enough space between PCi-E.
December 13, 2007 8:02:36 PM

Dear cb62fcni

No you do NOT need a special case there IS room to fit a dual slot board in the last slot of MOST cases you would put a setup like this in. First you would NOT put this in a mid-tower but in a full tower case that would be suitable for the rest of the equiopment you would be getting. Otherwise it is like a person that goes out and gets Bose speakers but goes to Radioshack for the AMP/Receiver. You must look at putting oranges with oranges and apples with apples. Coolermaster Cosmos and Stackers come to mind as cases that would lend themselves toa setup like this easily.

Motherboard configuration
slot 1 - PCI-E
slot 2 - whatever
slot 3 - PCI-E
slot 4 - whatever
slot 5 - PCI-E
slot 6 - whatever
slot 7 - PCI-E

Physically it is feasible with nothing custom-the real problem is will the GPU makers feel there is a big enough market to invest in the R&D. A more intelligent design is to put two GPU's on the same board then possibly put a special CPU on the (GPU)board to handle some of the overhead.

Considering a high-end card would be say $500, how many people would spend $2000(or more) for a quad video card setup for gaming with probably huge diminishing returns on the 3rd and 4th video cards? If they could co-opt the workststion market that would be a marketing point to consider for actually doing it. A lot of things ARE possible but the bottom line is will it bring a profit to the company. A lot of what gets "leaked" is simply a trial balloon to help them define the possibility of a niche in the current market. If they have to design new cases then that is defining a NEW market which is much harder to judge and a lot more risky.

GUESS WHAT the stacker and the Cosmos can fit the PHYSICALLY larger workstation dual CPU motherboards. It can be done with common 'off the shelf' parts, the biggest is if the companies feel there is a market big enough to invest in doing it. Another point about heat is that the 45nm process is taking care of that part along with the power requirements. I just built a Q6600 machine with ASUS Maximum Formula SE and dual ATI 3870's with lower power requirements than my old machine with 1 HD2900xt and E6400

BTW I have 2 ASUS workstation motherboards in Stacker and Antec cases
December 13, 2007 8:21:24 PM

Hey, aevm

Yes I am running 8 LCD's for my day-trading. My setup is tame, go to www.tradingcomputers.com to see some real monsters. Another company I know is offering platforms with 20 monitors. Matrox makes PCI cards that run 4 monitors as well as PCI-e cards that will do 4. I am using Nvidia 6800's, Asus P5W64 Motherboard. ATI also makes quad cards. You do not here a lot about them because they are aimed at the workstation market. Also cards are coming out for the 1x, 2x and 4x PCI-e slots. In general the x1 PCI-e has about 500MB/s while run of the mill PCI cards have 128MB/s. More than enough to be efective in these small slots. Matrox has cards that take advantage of the new PCI protocols and can run at 512MB/s in PCI for 2D work these are more than adequate throughput.
December 13, 2007 8:38:18 PM

hcforde said:

Motherboard configuration
slot 1 - PCI-E
slot 2 - whatever
slot 3 - PCI-E
slot 4 - whatever
slot 5 - PCI-E
slot 6 - whatever
slot 7 - PCI-E


Ok, let me rephrase my point: Without changing the stock cooler configuration, it is not only probably impossible to fit these dual-cooler cards in, it is highly inadviseable. In the configuration you so painstakingly drew out, the aptly named "whatever" slots would, instead of being filled with "whatever" house the stock cooling solution for the 3870's. Notice the lack of "whatever" below slot 7. This is the problem, coupled with the fact that in any conventional case the intake fan for the poor bottom card would be nearly flush with the bottom of the case. Do you appreciate what I was trying to get across now? Now, if you would invest in aftermarket cooling solutions for the cards, it becomes more feasable, but still completely silly since there's no drivers and the bottom two slots would likely have to run at x4 or possibly at x8. As you mentioned, the law of diminishing returns comes into play, mainly due to overhead scheduling issues as I mentioned earlier, but I would imagine bandwidth would also be a factor with 4 cards on the bus. Now, the X2 versions of the card seem to hold more promise, so we'll have to see when they get released whether ATI will support quad crossfire in drivers right away, or if we'll be forced to play the waiting game like we did with Nvidia and the GX2.
December 13, 2007 10:14:39 PM

Arent they still playing that waiting game.. waiting...


MSI board can use 4x 3870's already so can the big cases, whats the problem? Theyd work fine with stock cooling.

Bandwidth wont be a problem if they use good bridges, that is what they are there for.




Anyway, if people want performacne im sure they would quite happily do it, most would go with WC'ing on them anyway.

But for the guys with 2560x1600 im sure it would scale pretty well just like tri-sli which is scaling brilliantly at that high resolution.
December 14, 2007 2:10:21 AM

cb62fcni

You seem to be under the impression that the world ends after slot 7. That real estate ceases to exist. That at the edge of the motherboard there is no more space that can be used. As HATMAN said, as I have attemped to tell you the bigger stock cases can fit a dual slot card in slot 7 and all will be well. It has already been done NUMEROUS times. It is like you are saying that Quantum Physics does not exist because you can not understand it. If others understand it and can work with it--guess what, it exists. Those of us that have worked with dual-slot cards in slot 7 understand it. Your position has the potential to mislead others if read unchecked.
December 14, 2007 3:32:04 PM

hcforde said:
cb62fcni

You seem to be under the impression that the world ends after slot 7. That real estate ceases to exist. That at the edge of the motherboard there is no more space that can be used. As HATMAN said, as I have attemped to tell you the bigger stock cases can fit a dual slot card in slot 7 and all will be well. It has already been done NUMEROUS times. It is like you are saying that Quantum Physics does not exist because you can not understand it. If others understand it and can work with it--guess what, it exists. Those of us that have worked with dual-slot cards in slot 7 understand it. Your position has the potential to mislead others if read unchecked.


You're right, I don't believe in quantum physics, or even some aspects of Newtonian physics. For example, a photon has no mass, yet has momentum? Even Stevie Wonder can see that that is impossible.

Seriously though, I understand that it is possible to cram a double-slot card into the 7th slot, what I'm trying to say is that because of the design of about 99% of the cases out there, this would be impractical because #1, there is no place for the exhaust to vent out, and #2, the intake fan of the stock HSF would be sucking on the bottom of the case instead of moving air around. Sure, if you have a Stacker 830 or something, you could make it work, but 4 cards is far from an ideal solution regardless. That's all I'm trying to say. I'm not saying it's impossible, just that it's impossible with many of the cases that people use. Hokay?

And Hatman, the MSI X38 diamond board, which is the one I'm assuming you're referring to, has the two x4 PCIE 2 slots right next to each other, so one would have to use alternative cooling regardless. I'm really curious to see some benchmarks when the drivers come out, it seems like running at x4 would be somewhat limiting in certain scenarios (rendering, etc). Any thoughts?
December 21, 2007 2:17:11 PM

What about the Akasa Eclipse 62? That has 8 slots.

Thermaltake have also just released a case specifically for quad crossfire. It looks tacky as hell but has room for ten expansion slots, room for a big water licuid cooling unit to slot into the top and if you just want to air cool there are two plastic tubes throwing air to where the graphics cards are situated. It's called the Xaser VI

The armor + also from thermaltake would suit the quad crossfire platform as well.

December 21, 2007 2:33:54 PM

My stacker can take 8 it doesnt have the slot for t but they will fit in there fine, not like you need the 8th slot for the gpu anyway.
December 23, 2007 2:37:54 AM

Where does the hot air vent to if there is no eighth slot? If you have double-slot gfx cards, where the bottom slot is the vent, It goes right back into the crevice between the floor of the case and the heatsink/fan unit on the card. That said, there's also a severe deficit of available air intake real estate if all four cards are stacked like that. All of them have as little space to suck air as the card basically lying on the bottom of the case. A water cooling setup for four cards would also ring up to be pretty damn expensive, don't ya think? Even if you did, wher does the bottom half of the back plate go? Here's what it would look like from the back:

|{DVI:::}O{DVI:::}|1
|IIIIIIIIIventIIIIIIIIII|2^
|{:::::::}O{:::::::}|3
|IIIIIIIIIIIIIIIIIIIIIIIII|4^
|{:::::::}O{:::::::}|5
|IIIIIIIIIIIIIIIIIIIIIIIII|6^
|{:::::::}O{:::::::}|7
|........no vent.......|8^?

from the side:

|------card-------------------1
|_____________==inlet==_|
|-----------------------------3
|_____________=======_|
|-----------------------------5
|_____________=======_|
|-----------------------------7
:_____________=======_|
------------------------------------case bottom

I should hope some of you guys have seen dual-slot cards before, but only some of you saw the point of the physical limitations I was trying to drawing attention to.
!