Question for SLI Owners...

[perkam]

Ok so multi-vpu tech is evolving real fast and ATI will be getting into the mix soon enough too.

So a fundemental question about SLI. SO yes you can run two cards for benching and high fps but WHAT IF you want to run only one ???

As in to generate less heat and use less wattage. Do you have to take it out of the comp every time ur not using/dont want to use the second gpu or is there a way to disable the second PCIe slot completely ???

Thx in advance for answer ;)

Perkam

[sauria]

Well, I suppose you could uncheck the enable SLI in the control panel.

[perkam]

AMAZING !!! So Many Responses !! OMG !!! :rolleyes: ;) j/k

LOL I'm sure there are a lot more ppl with sli here at XS and I'm greatful for it.

Sauria you could disable the feature but the two cards would still be running, I want to know if you can turn it off completely without having to take it out of the slot :(

Perkam

[sauria]

I will try that for you.

[mdzcpa]

There is no way to disable the card. You can only choose not to run SLI in the driver. As long as the card is in the slot it is on and powered.

That said, I couldn't think of a reason that makes any sense as to why you would want that. It would be akin to underclocking your FX so as to save on wattage and heat. Furthermore, it would be silly to have invested the money and not run the hardware. It the concern is heat and wattage, then SLI probably isn't a good choice for the user in the first place.

[sauria]

Hey mdzcpa -- what brand of 2 x 6800U are you running?

[Arnar]

He has ASUS

[sauria]

Thanks, I'm looking for the best 2 x 6800 SLI cards now.

[sauria]

You can turn off the SLI mode but the fan still spins perkam -- it's "on" but now working.

[mdzcpa]

Thanks, I'm looking for the best 2 x 6800 SLI cards now.

The Asus are top dogs if you can find them. The core comes clocked standard at 425mhz (versus the typical Ultra core clock of 400mhz), and they OC great. I would guess that these chips have been binned to be the cream of the crop. I was getting 490mhz on the cores all day on simple water without any extra voltage.

[Disposibleteen]

You can turn off the SLI mode but the fan still spins perkam -- it's "on" but now working.
no, they both work but as seperate cards. This is how 4 monitors can be achived.

[conrad.maranan]

There is no way to disable the card. You can only choose not to run SLI in the driver. As long as the card is in the slot it is on and powered.

That said, I couldn't think of a reason that makes any sense as to why you would want that. It would be akin to underclocking your FX so as to save on wattage and heat. Furthermore, it would be silly to have invested the money and not run the hardware. It the concern is heat and wattage, then SLI probably isn't a good choice for the user in the first place.
Very well stated. ;)

[mdzcpa]

no, they both work but as seperate cards. This is how 4 monitors can be achived.

Correct. Like I said, if they are in the slot, they are powered on.

[perkam]

That said, I couldn't think of a reason that makes any sense as to why you would want that. It would be akin to underclocking your FX so as to save on wattage and heat. Furthermore, it would be silly to have invested the money and not run the hardware. It the concern is heat and wattage, then SLI probably isn't a good choice for the user in the first place.

My concern is heat and wattage because not everyone can buy a 600W SLI psu along with two vid cards and a mobo so running two high power req vid cards simultaneously 24/7 may not always be the best thing. But should that alone stop me from trying out SLI ?

The reason for my question was that if I decided to oc the cpu for a high super pi run I wouldnt need two gpus in the comp and they certainly wouldnt help with the heat 'n all. Secondly, if friends come over and want to see the difference between one vid card and two in sli/mvp mode, I really cant tell them to go visit some forums or something because if they need an explanation its really not for them to know :rolleyes:

But at any rate, MDZCPA, your input is always appreciated :bows: and if turning sli off with the two gpus running is the only way to do it then I'm quite sure there isn't any other way, though that means that my question now is this:

Is there a difference between benching one card only AND benching two cards with SLI OFF ??? Does having two cards EVEN with sli off provide increased marks or is it the same thing as having one gfx card ??

Perkam

[mdzcpa]

perkam,

Sorry if my above comment came off a little smart azz...that wasn't intended. I understand what you're after. But there is no easy way to do it. It would be just like wanting to show a friend how the FX would perform with just half the cache. Its just not something easy to do. For most purposes you just have to treat both video cards like one peice of equipment. And anyone going SLI should invest in all the supporting hardware (PSU, etc) if they want the best experience.

If you shut off SLI, both cards will still be operational. But you'll only be getting the performance of one card. So the answer is yes, two cards installed without SLI will run the same speed as one card. However, other complicationg factors is that you'll need to remove the bridge (easy) and change the jumpers on the board (not easy with the cards installed) to go No-SLI.

Bottom line, there is no quick way to jump back and forth between SLI and no-SLI. Again, my humble advice is to treat both cards as a single unit. Although comparsions on the fly would be nice, it just isn't practical. Comparisons can easily be done....just not on the fly.

[sauria]

The Asus are top dogs if you can find them. The core comes clocked standard at 425mhz (versus the typical Ultra core clock of 400mhz), and they OC great. I would guess that these chips have been binned to be the cream of the crop. I was getting 490mhz on the cores all day on simple water without any extra voltage.
Thank you, how to they clear each other on your board?

[mdzcpa]

Here's a pic:

http://www.xtremesystems.org/forums/attachment.php?attachmentid=26638&stc=1

[perkam]

perkam,

Sorry if my above comment came off a little smart azz...that wasn't intended.
:bows: Not at all. I was fortunate enough to have you answer my question MDZ, I know for a fact your expertise in the sli area and always great to hear from you. I can also understand your frustration in having discussed and argued so much stuff on the subject only have someone like me ask such a newb question LOL.


So the answer is yes, two cards installed without SLI will run the same speed as one card.
Just what I wanted to hear :up:


Bottom line, there is no quick way to jump back and forth between SLI and no-SLI. Again, my humble advice is to treat both cards as a single unit. Although comparsions on the fly would be nice, it just isn't practical. Comparisons can easily be done....just not on the fly.
Point Taken ;) So I guess wanting to have sli isnt the same thing as wanting the performance of two cards as opposed to one but instead wanting double the performance of one card 24/7. Understood then.

So the only way to really know the difference is to physically remove the gpu then? That's fine with me. I imagine as the software for sli evolves so will the options and features pertaining to its use/non-use so I'll just have to wait and see.

My reason for asking was that I imagine ATi probably reverse engineered Nvidia SLI LOL or at the very least has the same fundamental limitations but I can understand how you just cant turn an entire slot "OFF" without taking the card out. THe SLi bridge yes would be no problem other than the jumpers.

THis makes it more problematic when showing to friends who may not understand what benches and scores really mean and thus the perf. difference between one and two cards is pretty much all that will "wow" them. At any rate, yes its neither practical nor necessary just something I never knew if SLI was capable of.

P.S. Sorry for late reply.

Perkam

[mdzcpa]

Sitting back and thinking about it, your question really was a good one. I'd like to be able to flip back and forth quickly to see what the performances differences are. Sure would make testing and tweaking easier as well.

If ATI does a software only design without bridges and mobo jumpers, than flipping back and forth will be easy. You'll still have the power up issue with a vid card in the slot using wattage, but for performance comparisons it would be easier.

Also, just to make sure your question was thoroughly answered, the Nvidia SLI can be disabled in the software too. Trouble is, with the SLI bridge in place, and the jumpers in SLI mode on the mobo itself, I wouldn't be comfortable relying on the results being exactly what would be seen if only one card was installed with the jumpers on the board in non-SLI position. I haven't compared the performance of those two configurations to know. What I did compare was performance for a single card installed (with jumpers in Non-SLI) vs. two cards installed (with jumpers in non-SLI) and they were the same.

It may be possible that by just unselecting SLI in the driver, and leaving the jumpers and bridges in place, that you can measure single card performance. However, my gut instinct tells me it wouldn't be representative of single card performance. If it was, we wouldn't have the bridge and jumper to contend with in the first place:)

[perkam]

What I did compare was performance for a single card installed (with jumpers in Non-SLI) vs. two cards installed (with jumpers in non-SLI) and they were the same.
Thats Great if they give the same perf and it really doesnt matter I guess if the performance is little bit more than having one card, no jumpers, no sli, cos I imagine its just going to be like a slight oc or something.



However, my gut instinct tells me it wouldn't be representative of single card performance. If it was, we wouldn't have the bridge and jumper to contend with in the first place
As does mine, hence my question. Previously I had stated I didnt even like using two cards because of comparative purposes with one cards etc etc but it seems sli/mvp is a feature that is hard to ignore when you're looking to have the best score ;) So I'll probably give it a go with ATI and find out for myself for sure.

In any case, this does bring up another point. Seeing as how SLI gives a perf boost in 03 and 05 but not considerably in 01, perhaps the replacement for 01 (from OPP's thread) should be one that isnt influence by two gpu's or one, just like 01se was. Though knowing ATI, two gpus may make a world of difference in 01 but highly unlikely.

Perkam

[mdzcpa]

01 isn't effected because it just doesn't take advantage of the real power of SLI...that being the ability to run massive framerates using the latest directx 9 technology (complex shaders, etc). 01 wasn't designed not to be affected by SLI, its just too old of technology (DX8) to be affected. There are portions of the DX9 compatible GPU that don't even get used running 01.

Moving forward, I'm quite sure that all future benchmarks will be positively and heavily affected by SLI because they will be using new software technologies that current GPUs can run, or will run.

[gundamit]

01 isn't effected because it just doesn't take advantage of the real power of SLI.... And yet I seem to recall seeing reviews of SLI set-ups that had Nature jumping up a bit. I've tried it with my BFG 6800GTs and have seen no increase over a single card.
Link to Lost Circuits Review (http://www.lostcircuits.com/video/6600gt_sli/5.shtml) Anyone seeing an increase on Nature with SLI?

[sauria]

I'm not with two MSI 6600GT's

[Vapor]

I think you have to make your own SLI profile to get it to work in 01. CPU overhead will probably knock the score down as much as the second GPU will raise it.

[J-Mag]

change the jumpers on the board (not easy with the cards installed) to go No-SLI.



you wouldn't HAVE to change the jumpers, b/c you could just run the single card on the bandwidth of an 8x pci-e slot fine...

[texuspete00]

Here's a pic:

Nice setup. How much of it is 1/2" ID and how much is 3/8". I have a 1/2"ID setup now and might need to add SLI. I guess all 1/2" ID won't work no matter the kind of tubing?

[mdzcpa]

I think you have to make your own SLI profile to get it to work in 01. CPU overhead will probably knock the score down as much as the second GPU will raise it.

Overhead for SLI is 1%, per Nvidia.

[mdzcpa]

you wouldn't HAVE to change the jumpers, b/c you could just run the single card on the bandwidth of an 8x pci-e slot fine...

That would make that configuration NOT equivalent to running with a single card with the jumpers in non SLI mode. And that's the comparision perkam is trying to make. Bottom line, if you want to compare SLI to single card performance, the jumper must be set for non SLI for single card use.

[mdzcpa]

Nice setup. How much of it is 1/2" ID and how much is 3/8". I have a 1/2"ID setup now and might need to add SLI. I guess all 1/2" ID won't work no matter the kind of tubing?

It's all 3/8's which is more than enough to handle two GPUs. The CPU is cooled by the Mach II. The GPUs are cooled by two MCW-50 blocks, MCP600 Pump, and the Swiftech twin 120mm fan radiator.

http://home.comcast.net/~mdzcpa/images/forumpics/DFISLI/DFISLI.JPG

I think 1/2 tubing would be cumbersome and overkill for two GPUs.

[J-Mag]

Yeah, that post of mine was deinfately just for argument's sake (or boredom at work... i dunno)

Anyway, the whole argument is pretty much worthless cause if you got two cards and an SLI board why the hell woud you ever run just one?

The thing I am interested in is how overclocks change in SLI mode.

For instance my GT's can reach the following overclocks with the nvidia test determining the breaking point:
GT #1 : 425 1180
GT #2 : 420 1170
SLI : 417 1130

So why is it that I cannot run 420 1170 ? I am thinking it might be power related ( when both 6800GT's are in the rig I have to share molex lines with other devices and the cards )

Have you noticed a similar effect?

[mdzcpa]

The thing I am interested in is how overclocks change in SLI mode.

For instance my GT's can reach the following overclocks with the nvidia test determining the breaking point:
GT #1 : 425 1180
GT #2 : 420 1170
SLI : 417 1130

So why is it that I cannot run 420 1170 ? I am thinking it might be power related ( when both 6800GT's are in the rig I have to share molex lines with other devices and the cards )

Have you noticed a similar effect?

This is an excellent question.

I have experienced a very small decrease in overclockability in SLI as well. Not bad though. On my Asus 6800U, both cards ran up to 495/498 on water. The best they can do in SLI is 490 without artifacting. memory overclocks for me did not change.

Now, what is really interesting is that before I switched my PSU (to the PCP&C 510 SLI) I was further limited...by a lot. My cores would not go any further than 470 or so without heavily artifacting. I switched from the Antec NEO to the PCP&C SLI and gained almost 20mhz per core.

The moral of the story is that stable and plentiful power supply is critical when you have that much hardware OC'd to the max.

[J-Mag]

I switched from the Antec NEO to the PCP&C SLI and gained almost 20mhz per core.

The moral of the story is that stable and plentiful power supply is critical when you have that much hardware OC'd to the max.

What was the 12v rail on the Neo?

Did the NEO have dedicated lines for the PCI-E cards, or did you have to use molex converters? If you were using molexes, were all four on their own dedicated unshared lines?

I had seriously considered testing this theory out soon. I wanted to try out the 700W Zippy, but I was hoping they would come out with one that has two PCI-E connectors. Currently I am using only the 400w Zippy, but it has 30amps on the 12v rail, so that should be enough...

Edit: BTW, are you just seeing artifacting from your vid card overclocks, or have you been seieng any lock-ups, BSODs, Crashes?
I have noticed with my older equipment (9800pro) I will always get artifacts form overclocking and rarely any game crashes, unles sit has been artifacting for a while already). It seems with my SLI rig I am prone to crashes and freezes when trying to push the cards overclock, somestimes with out any artifacts first...

[sauria]

This is an excellent question.

I have experienced a very small decrease in overclockability in SLI as well. Not bad though. On my Asus 6800U, both cards ran up to 495/498 on water. The best they can do in SLI is 490 without artifacting. memory overclocks for me did not change.

Now, what is really interesting is that before I switched my PSU (to the PCP&C 510 SLI) I was further limited...by a lot. My cores would not go any further than 470 or so without heavily artifacting. I switched from the Antec NEO to the PCP&C SLI and gained almost 20mhz per core.

The moral of the story is that stable and plentiful power supply is critical when you have that much hardware OC'd to the max.
Excellent info. I am very pleased with that PCPowercooling 510 SLI as well. It must but putting out the power as the exhaust is always warm! Great heatsinks on quality components.