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blueworm
09-08-04, 03:50 PM
Title says it all. Will 2 Geforce6600 in SLI at about 400 USD the pair, faster than a Geforce6800 Ultra?
I realise that this wont be practical until nforce4 shows up and that the board will have
an extra price, but nevertheless...

kyleb
09-08-04, 03:52 PM
I don't see how they could be. I mean SLI will obviously help peformace but it is not like the cards get to share everything, Texture memory will have to be seprate on each card and that will cut into bandwidth as well.

Sazar
09-08-04, 03:54 PM
in lower LOD situations... perhaps it will be close...

@ higher LOD I think it might still lag behind...

from the descriptions it seems in best case scenarios SLI == 1.8-2x performance of single card... I am taking this with a grain of salt as I do anything that has not been corroborated and verified :cool:

but potentially you could see some nice performance in the future edging upto the levels of a 6800gt perhaps in select situations...

Cota
09-08-04, 03:58 PM
I think it will beat it in some games and loose in others depending on the settings used.

Since it only has 128mb gaming at 1600x1200 with 4xAA/8xAF will probably be much slower than the ultra but at 1280x1024 it could be as fast or maybe faster.

Clay
09-08-04, 04:22 PM
I asked this very question to some folks that know...I didn't get a direct answer. The most I could get was "possibly". :)

Subtestube
09-08-04, 05:00 PM
nVIDIA claim the SLI performance gains are around 1.8 (I think 1.87 was the number they said)... so I guess the answer is *possibly*.. but yes, you're still going to be very memory limited as each card'll need a copy of everything.

Pantherman
09-08-04, 07:47 PM
It doesn't seem likely that two 6600 GTs will be able to beat a 6800 Ultra. You're still stuck with the 128MB memory interface. It would be interesting to see how those two 6600 GTs would do against a single 6800 GT. It's great to see SLI back again. It would be interesting to see two 6800 Ultras working with SLI.

BuzzLightyear
09-08-04, 07:52 PM
The memory limitation theory doesn't make sense. If your card has 128mb and can run a 3D scene on one card, then it's still only going to require the 128mb per card to render the same scene.

The point of the 6x00 SLI is that it divides the maths as equally as possible between the cards.

Whether 2x6600 cards is faster than an Ultra card is kind of irrelevant, because 2x6800U cards is going to be even faster. If you want ultimate performance and have the moola you aren't going to settle for the lesser pair - as it is now with the 6800 vs 6800U.

MUYA
09-08-04, 07:55 PM
1.8 is best case sceneario IIRC. Pantherman is correct, you are still stuck with a 128 bit memory interface and on top of that even though u have 2 cards with 128 MB, the SLI setup mirrors the data between teh two cards and u have a usable 128MB of memory only...IIRC from what NV were saying

photophreak314
09-08-04, 08:01 PM
As far as memory goes, I don't believe that all the data and textures will be cut in half and sent to each card as little chunks, as many textures will be needed once the portion of the screen that has certain things in it moves the the other cards part. It would make sense just to load up everything to each, where the 128mb would be a limit at higher resolutions, but not at "regular" resolutions. Did that make sense? All of a sudden I'm confused and don't know if that's quite accurate.

Anyways, why would you get two 6600/6600GT's when you could buy 1 6800 Ultra or GT, and get the same performance, but wouldn't need a new mobo or a new powersupply or something to enable them to run.

fivefeet8
09-09-04, 01:23 AM
http://www.anandtech.com/video/showdoc.aspx?i=2097&p=3

Nvidia's SLI splits the amount of work 50/50 per video card in SLI. Both cards needs to finish processing their respective parts at the same time.

kyleb
09-09-04, 02:17 AM
It isn't 50/50, it splits it by workload. But again, both cards need to load the textures and send them to the respective gpu's; so memory space and bandwidth will be far less than double.

Arioch
09-09-04, 02:36 AM
I think running two 6800GT cards in SLI is the way to go for me.

BuzzLightyear
09-09-04, 08:39 AM
It isn't 50/50, it splits it by workload. But again, both cards need to load the textures and send them to the respective gpu's; so memory space and bandwidth will be far less than double.

But once your textrures are loaded, each card has them. There's no bandwidth issue once they are on the GPU memory, unless you need to setup new textures for some reason, but that isn't often.

And why does everyone keep saying memory is going to be limited? If your first card had 128Mb, your SLI setup will have 128Mb.

From the end users point of view, an SLI 6600 is simply going to make your 6600 run faster - that's it - no more memory, no more features, nada, zip, just faster.

MUYA
09-09-04, 08:46 AM
And why does everyone keep saying memory is going to be limited?
why does it irk u so much that it's asked bud? Some ppl are not technically adept..including me and thats the point maybe of this thread. You understand it great but let others who do not fully understand it ask. k thanks

anzak
09-09-04, 09:58 AM
By the time a dual PCIe system is available (nforce 4) the 6800 should cost around $250 street. That's 24 pipes for $500 not bad IMO.

jbirney
09-09-04, 10:39 AM
Dont get memory bandwidth mixed up with total memory.

Both have different limitation.

For example given NV SLI it seems like both GPUs need to have all of the memory requirements of a sceen as it does not know before hand which part of the scene it will render. Thus if your game has memory requirements that exceed 128mb, then both cards will have to fetch textures from the slower interfaces (APG/PCIe vrs internal memory).

Then there is a memory bandwidth limitation. The slower 128 bit interface will mean that it will take "longer" for the GPU to complete rendering of its part. The interesting thing is that the amout of rendering a GPU has to do is less. So question is how much less work is it doing and can that offset its memory bandwith?

fivefeet8
09-09-04, 11:48 AM
It isn't 50/50, it splits it by workload. But again, both cards need to load the textures and send them to the respective gpu's; so memory space and bandwidth will be far less than double.

Isn't that what I said? It splits the workload by 50/50.

zoomy942
09-09-04, 12:19 PM
this SLI is awesome, but it reminds me of the voodoo 5 5500 i had. i had 2 vsa-100 chips, and 64 megs of memory.. but each vsa had 32 megs to play with.. it duplicated the textures in each one. we can relaly see 3dfx showing up nvidia now

Cota
09-09-04, 01:12 PM
SLI has 2 modes for rendering on 2 cards

split screen where 1 card renders top "half" and the other bottom "half".

AFR or Alternate Frame Rendering where 1 card renders one entire frame while the other renders the next.

npras42
09-09-04, 01:32 PM
I thought that's what Alienware's new Motherboard technology was supposed to do (which should be compatible with any AGP or PCIe graphics cards) not what SLI is, where it splits by worlkload as explained above.

Well that's what I understood of it anyway.

Edge
09-09-04, 01:44 PM
SLI has 2 modes for rendering on 2 cards

split screen where 1 card renders top "half" and the other bottom "half".

AFR or Alternate Frame Rendering where 1 card renders one entire frame while the other renders the next.

Really? Huh, that's actually a kinda bad way of doing it...what if one part of the screen has more graphically intense data on it (like if you're looking at a forest, and the top half of the screen is just sky but the bottom half is the landscape)? Then the split screen mode would kinda be useless. Also the AFR sounds like it would add an extra 1fps latency to the system, since it would have to stay 1 frame ahead of user input. Hmm, almost seems like 3dfx's method of alternating scanlines is superior to Nvidia's SLI method, go figure :)

ynnek
09-09-04, 01:48 PM
Another example would be an in ****pit view of a car or flying sim.. the ****pit stays the same on the bottom, but the bulk of the work is happening on the top..

I remembr reading they are trying to get the cards to load balance dynamically, moving the split up or down..

Really? Huh, that's actually a kinda bad way of doing it...what if one part of the screen has more graphically intense data on it (like if you're looking at a forest, and the top half of the screen is just sky but the bottom half is the landscape)? Then the split screen mode would kinda be useless. Also the AFR sounds like it would add an extra 1fps latency to the system, since it would have to stay 1 frame ahead of user input. Hmm, almost seems like 3dfx's method of alternating scanlines is superior to Nvidia's SLI method, go figure :)

fivefeet8
09-09-04, 02:03 PM
Nvidia's method isn't really splitting the screen in half 50/50, but is splitting the screen dependant on the amount of work each half would take to process at the same time.

Cota
09-09-04, 02:38 PM
Really? Huh, that's actually a kinda bad way of doing it...what if one part of the screen has more graphically intense data on it (like if you're looking at a forest, and the top half of the screen is just sky but the bottom half is the landscape)? Then the split screen mode would kinda be useless. Also the AFR sounds like it would add an extra 1fps latency to the system, since it would have to stay 1 frame ahead of user input. Hmm, almost seems like 3dfx's method of alternating scanlines is superior to Nvidia's SLI method, go figure :)

I said "half" meaning that each card makes half the job not precisely half the image.