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First post, by RaiderOfLostVoodoo

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This question is going through my head for some time.

For those who don't know it:
In 3dfx SLI (Scan Line Interleave) one card calculates every even row (1+3+5+7+etc) while the other calculates the odd ones (2+4+6+8+etc).
In nVidia SLI (Scalable Link Interface) each card calculates one half of the screen. Don't remember if was top+bottom or left+right.

From my point of view 3dfx SLI is a more elegant solution, because it distributes the load evenly between both cards. In nVidia SLI, if you have an explosion in one half of the screen, one cards gets stressed while the other is idling around. That seems highly inefficient.
So why doesn't nVidia do it like 3dfx did? Are there advantages in nVidias method that aren't obvious?

Reply 1 of 14, by Kreshna Aryaguna Nurzaman

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I think it's because 3dfx cards are pure rasterizer. They only have to deal with textures and texture-related jobs. As such, it's quite easy to split the load evenly between both cards using odd and even lines.

nVidia cards, on the other hand, are full-fledged GPUs. They also have to process geometry (transform & lighting, vertex shader, and what-have-you) as well as textures. I don't think it's easy to split geometry-related loads into odd and even lines, hence the SFR and AFR approach.

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Reply 2 of 14, by matze79

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SuperTiling maybe is the closest thing to 3Dfx SLI.
Crossfire used it.

https://docs.nvidia.com/gameworks/content/tec … desktop/sli.htm
I remember weird Problems with NVIDIA Sli on Dual 6600GTs.
Like a Horizontal Line in the Middle of the Screen / Tearing.
I don`t know how it is today. Did not use a SLI Setup in Years.

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Reply 3 of 14, by FioGermi

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I miss SLI. I mean, i never partook in it myself with modern GPUs because of how expensive it was. But i always liked the look of 2 beefy cards in a system and performance seemed to scale pretty well if the game developer actually bothered to optimize for it. It was the dream growing up.

Now its just a dead meme.

Reply 4 of 14, by weldum

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FioGermi wrote on 2022-04-15, 22:44:

I miss SLI. I mean, i never partook in it myself with modern GPUs because of how expensive it was. But i always liked the look of 2 beefy cards in a system and performance seemed to scale pretty well if the game developer actually bothered to optimize for it. It was the dream growing up.

Now its just a dead meme.

sadly both sli and crossfire were never widely supported by game developers, surely you can force to work in some games, but in worst case scenario the performance is outrageous
3dfx sli, as it was said, works as the voodoo cards are pure rasterizers, so the load is more balanced
other plus to that approach was that the heavy work of splitting the data and resources was done at driver level, so the games only see a voodoo card with more or less memory and so on, that way it works in most if not all games, and in all graphical api, and it scales really well

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Reply 6 of 14, by The Serpent Rider

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In nVidia SLI (Scalable Link Interface) each card calculates one half of the screen.

That was dropped very quickly in favor of AFR, which was infamously used on ATI Rage MAXX.

Are there advantages in nVidias method that aren't obvious?

Nvidia SLI is purely digital solution, while 3dfx isn't.

SuperTiling maybe is the closest thing to 3Dfx SLI.
Crossfire used it.

Only hardware Crossfire used it and that thing required master card with a special cable to sync rendering.

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Reply 7 of 14, by TrashPanda

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leileilol wrote on 2022-04-16, 01:37:

given how much memory/pixel read ops are done by software for whatever screen effect, any dual+ gpu solution's doomed to be trash.

MGPU has replaced both Xfire and SLI for modern GPUs and considering how powerful it is as an API I dont ever expect SLI or Xfire to ever become a "thing" again for gaming, that said as powerful as it is it does require a ton of work on the developers part to implement, it also requires that the GPU hardware supports DX12U. SLI is still around but only on the flagship eye wateringly expensive nVidia GPUs and for gaming its pretty much useless as even one 3090 is overkill for the vast majority of games.

Funny thing is that both AMD and nVidia are moving to a hardware MGPU setup with multi GPU cores on the one card appearing to the OS as one monolithic GPU so even DX-MGPU wont become a huge thing in the consumer space, the next round of GPUs are rumoured to be 600watt behemoths so running more than one in your gaming PC will be akin to having a heat pump on your desktop.

Still .. 3DFX certainly did have a nice solution for multi GPU rendering and I still love my Voodoo2 SLI setup, I wish they had survived long enough to get their Voodoo5 6000 and Rampage to market, would have been fun to see 3DFX stick it to nVidia and ATI.

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Reply 8 of 14, by Cuttoon

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While I'm not quite sure how DVI and DP signals work, I could imagine that 3dfx SLI only worked with a VGA signal. Since that had, well, scan lines.
If not, then it still seems plausible that messing with the scan lines between devices leads to all kinds of HF-typical issues at higher frequencies, i.e. resolutions.

Look up "interlacing" and what creative ways of fuckuppery that generated when trying to somehow transform the signal in any way.
Analogue video transmission is a mess.

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Reply 9 of 14, by TrashPanda

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Cuttoon wrote on 2022-04-16, 02:46:
While I'm not quite sure how DVI and DP signals work, I could imagine that 3dfx SLI only worked with a VGA signal. Since that ha […]
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While I'm not quite sure how DVI and DP signals work, I could imagine that 3dfx SLI only worked with a VGA signal. Since that had, well, scan lines.
If not, then it still seems plausible that messing with the scan lines between devices leads to all kinds of HF-typical issues at higher frequencies, i.e. resolutions.

Look up "interlacing" and what creative ways of fuckuppery that generated when trying to somehow transform the signal in any way.
Analogue video transmission is a mess.

Interlacing .. that abomination should have never existed as a tv standard

Oh noes, the cap let the shmooo out 😁

Reply 10 of 14, by Gmlb256

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TrashPanda wrote on 2022-04-16, 02:31:

SLI is still around but only on the flagship eye wateringly expensive nVidia GPUs and for gaming its pretty much useless as even one 3090 is overkill for the vast majority of games.

SLI was replaced by NVLink. Still it is overkill for games and these solutions are more targeted towards GPGPU and HPC stuff.

I wish they had survived long enough to get their Voodoo5 6000 and Rampage to market, would have been fun to see 3DFX stick it to nVidia and ATI.

If these products were actually released to the market, it would be too late to compete with ATi/AMD and nVidia in terms of features. And Voodoo5 was already expensive so the Voodoo5 6000 won't do any favor.

Reply 12 of 14, by TrashPanda

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Gmlb256 wrote on 2022-04-16, 03:25:
SLI was replaced by NVLink. Still it is overkill for games and these solutions are more targeted towards GPGPU and HPC stuff. […]
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TrashPanda wrote on 2022-04-16, 02:31:

SLI is still around but only on the flagship eye wateringly expensive nVidia GPUs and for gaming its pretty much useless as even one 3090 is overkill for the vast majority of games.

SLI was replaced by NVLink. Still it is overkill for games and these solutions are more targeted towards GPGPU and HPC stuff.

I wish they had survived long enough to get their Voodoo5 6000 and Rampage to market, would have been fun to see 3DFX stick it to nVidia and ATI.

If these products were actually released to the market, it would be too late to compete with ATi/AMD and nVidia in terms of features. And Voodoo5 was already expensive so the Voodoo5 6000 won't do any favor.

That's true Rampage was way behind schedule, but its not like both ATI/AMD and nVidia haven't had their horribly delayed GPUs either, hell AMD spent 10 years lagging behind nVidia and has only recently been back on a competitive footing performance wise so I doubt that a delayed Rampage would have caused too many issues assuming 3DFX hadn't bungled shit.

That said .. nVidia wouldn't be where they are now if they hadn't bought out 3DFX and rolled their tech into GeForce GPUs so its hard to say exactly how the market would have been if 3DFX had been competitive and survived. 3DFX had some amazing engineers working for them, I can just imagine how things would be now if we had three major players in the GPU market .. wait make that 4 since Intel is also part of it. (God damn it Intel your ARC GPU had better not be trash like i740)

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Reply 13 of 14, by havli

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From the known info, Rampage probably would be similar to GF3 performance wise... but using 2 or 3 chips instead of one and on less advanced process node (180nm). So power hungry and more expensive to make. Also the existing prototypes made at the very end of year 2000 barely worked and surely contained number of bugs (inverted RGB signals for instance). Getting Rampage to market would take half a year at least. Long after GF3 and perhaps at the same time as R8500.

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