So, as a follow-up to my recent video where I took two GTX 580s, threw them on
the Gigabyte G1 Gorilla motherboard, and I tested in dual 16x mode in SLI and
dual 8x bandwidth mode in SLI. I am
going to be taking an even higher an even more demanding card, the Radeon
HD6990, and I'm going to be running it in a single card configuration in a 16x
slot, an 8X slot, and finally a 4X slot
to find out what difference there is. In terms of performance, I'll be using the
3D Mark 11 extreme preset. Now, please
note that the extreme preset will not show as much of a difference as one of
the lower quality presets, uh, such as
the entry or performance presets. But what it does give us is a more realistic
real world scenario because most people are not going to be using a 6990 to run
Quake 3 at 1024 x 768. So, you're going
to be turning up the details, you're going to be turning up the res. So, that is the scenario that we will be looking
at. Something to bear in mind before I get too far into my testing here is that
the top slot at 16 and the second slot at 8X are both running off the PCI
Express controller integrated into the Sandy Bridge CPU on this board which is
clocked at 4.7 GHz by the way to eliminate any CPU bottlenecking or as
much as possible. The bottom slot actually runs off of the chipset at 4x
speed. So, it has an additional disadvantage that is not shared by the
top two slots. So, just bear that in mind. Take the results with a bit of a
grain of salt, but I don't have another platform handy where I can show you 16x,
8x, and 4x where they will all be equal.
So, my 16x result is a score of
3,330. So, I'll be back with 8x and 4x
results shortly. Now, this may look like a stupid configuration. I've got my 6T90
and a GTX 580 here. But the reason I've installed the GTX 580, which won't
affect my benchmark scores in any way, is to force these PCIe lanes to go from
16x to 8x8x. So, you can see here within
GPUZ, the 6990 reports as running at
16x. And while that may be true because
it's running internal Crossfire where each GPU is getting 16x bandwidth from
the uh from the lane spplitter that's on the PCB
itself. The actual lane splitter itself is only
getting if we look here at the GTX 580.
So you can see that the actual bandwidth to the slot is only 8x because it is
correctly split at this time. So my benchmark results are
3,312 3D marks. So we have seen
a difference in performance between 16x
and 8x
312. Okay, very small, very small. And I
will be back with PCIe 4X results very
shortly. So at the end of the day, this video becomes more about how if you
internally bottleneck a card um
according to the computational resources
located on the card that the amount of PCI Express bandwidth you supply it with
is actually going to make very little difference in terms of performance. Now,
something to bear in mind too about this particular testing setup today. You can
see I had to nudge my motherboard over a little bit to get the uh 6T90 to fit
into that bottom slot on my tech station. But so, I've got it in the PCIe
4x slot. Now, think about it this way.
Basically, I've got two GPUs. I have on a 6990, I pretty much have two 6970
GPUs. Okay? So, so bear with me here.
So, by the comparison I did the other day where I was comparing
16x6 and 8x8x SLI, this is basically running it
on this motherboard, this card in 16X mode is pretty much like running two
cards, two high-end single GPUs at
8x8x, 4x4x in the 8x slot, and then at
2x 2x in that 4x slot at at the very
bottom that that's essentially the amount of bandwidth we have available
per GPU and we still see very very
little fluctuation in terms of the overall score. So, what I may have to do
in the coming uh next little while is do
an updated video about this where I find a slightly less uh GPU speed
bottlenecked benchmark and uh demonstrate maybe more of a more of a
typical or worst case scenario for how much the PCI Express bandwidth affects
single card performance. So, thank you for checking out this little episode of
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