when NVIDIA bought out the defunct company 3dfx they acquired their patents
and intellectual property including the trademark sli name that had been used to
describe 3dfx's system for using multiple graphics cards working together
to achieve better gaming performance but
by the time they reintroduced sli to consumers its underlying technology had
undergone some very significant changes
let's see just what made the very first generation NVIDIA sli tick
after this message from our sponsor that keeps Linus tech tips ticking
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all right so in the late 90s 3dfx made a handful of now famous blunders first
they decided to manufacture their cards themselves as opposed to just selling
chips and providing reference designs to add and board partners but
because their new factory couldn't compete on either quality or cost with
taiwanese and chinese-based aibs oem relationships that they had hoped
would come never materialized two their focus on raw horsepower rather
than modern features allowed NVIDIA to steal the market share crown from their
flagship voodoo three then put the nail in their coffin with
the GeForce 256 which arrived earlier to
the market and was vastly technologically superior to the delayed
napalm core that they used in the voodoo 4 and voodoo 5.
3dfx filed for bankruptcy in 2002. so
then it only took two years for NVIDIA to decide that selling two graphics
cards rather than one per customer is pretty cool and roll out sli
again except that this time it stood for
scalable link interface rather than scan
line interleave this is because instead of having each card render alternating
lines of a single frame NVIDIA opted to use two new approaches
to splitting the rendering load between the two cards
in alternate frame rendering or afr
each card takes turns rendering a full frame this was the preferred method and
typically resulted in the best performance scaling and in split frame
rendering or sfr the 3d scene would need
to be broken down horizontally depending on geometry load with one card assigned
to render the bottom part of the frame while the other handled the top now via
both of these methods whether it was outputting half of every frame or
alternating full frames the secondary card would send its output to the upper
or mastercard via the brand new 400
megahertz one Gigabyte per second sli
connector then that top card would output the final image to the screen
now it was this high bandwidth connection that gave NVIDIA's solution
both its name and its high performance or well
sometimes high performance you see without a software sli profile the
second card would remain either completely unused or even end up hurting
performance and because the system had no way of knowing
on its own which sli rendering settings would work
best for a given game it was up to the driver team to hand validate both brand
new games and some significant older titles so this process was more work
than you might think and it wouldn't be until many driver updates later during
the summer after launch that the green team would ship their 100th sli profile
now let's talk about the hardware during the first unveiling NVIDIA was
actually using a xeon platform based on the 7525 chipset for its newfangled
high-speed pci express expansion slots
but despite these demos being originally run
on an Intel chipset NVIDIA ended up requiring users to
purchase a motherboard that was equipped with an sli ready variant of NVIDIA's
own enforce4 chipset now
the successful user modification of non-sli certified boards
raised quite a few questions about whether this was an artificial
limitation designed to help NVIDIA maintain a foothold in the chipset
market but i digress
the next thing you needed was a powerful CPU to keep both cards well fed with
data so we're using an overclocked opteron that will give us similar
performance to the fastest CPU at the time the single core 2.6 gigahertz fx 55
third a good 24 pin atx power supply was
strongly recommended now the 6800 gts
that we have in here their TDP is only 67 watts and our whole system pulls only
about 260 watts from the wall under load
but there's more to a quality power supply than just wattage one having a
suitable 12 volt rail distribution was absolutely necessary to keep it from
just turning off when you fired up a game and two
native pci express power connectors were a definite bonus at the time so you
didn't have to use adapter dongles onto the cards themselves sli technology
required pretty much identical cards
like this pair of matched xfx 6800 gts
and initially even the BIOS revisions on
the cards needed to be the same though that did ease up over time to the point
where even slightly mismatched cards would equalize according to the clock
speeds of the slower card finally a well ventilated case was a
must most of the cases from this era used 80
millimeter cooling fans so especially given the poor design of the reverse
blowing single slot cooler on our card
it was common to see side intakes modified into cases after the fact like
this one and even with our extra airflow
our cards hit a toasty 85 degrees under
load now let's look at performance NVIDIA
cited 1.87x scaling in synthetic benchmarks
but our own testing gave us 1.64 1.82
and 1.76 though it should be noted that when it
comes to real games we actually managed an amazing 1.98
scaling in half-life 2 and we saw up to 1.86
in far cry so in essence
this tech when it worked would enable you to step up to the next
image quality and or resolution level and what's cool is that the higher the
load the better it scaled furthermore unless it ran out of vram
which does not add up between the cards it's cloned the system took games from
the next gen like fear which was so
demanding it initially shipped with a 1024 by 768 maximum resolution from
cinematically playable to actually playable and before you ask
yes yes indeed it can at a mixture of medium
to low settings this machine produced over 40 FPS at 1024x768
in a game that came out three years
after this card launched neat right
now let's talk downsides and there were plenty the expense of a fast
CPU sli ready board and power supply aside
alternate frame rendering introduced a temporal artifact known as micro
stuttering where the frame rates were high but some users reported choppy or
jittery in-game animations and
this tech lived and died by the existence of an sli profile with some
games whether by design or due to just
not getting around to it never ending up working with sli meaning
that that second card that you bought was a terrible value if your favorite
game didn't end up scaling furthermore there were some general
quality of life issues including but not limited to the fact that two cards is
louder than one changing sli modes required a system
reboot at the start your second monitor would go black once the game was full
screen and i had this bizarre issue with azurius bittorrent client remember that
where it and firefox if they were running at the same time sli would
disable itself but still show enabled in the control panel and the list kind of
goes on so bottom line despite its first generation flaws
sli when it worked was so powerful that
it exceeded NVIDIA's next generation 7900 gtx's performance making it really
freaking cool when it worked
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so thanks for watching guys massive shout out to benoit pierre for sending
us a working sli motherboard for our test if this video sucked you guys you know
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