all right i'm going to take another crack at my PCIe 16x versus 8x versus 4x
testing this time i'm going to use a couple of games that i've benchmarked
quite a bit in the past we're going to go with battlefield bad company 2 as
well as metro 2033 since i had people
asking for not a purely synthetic test so i'm going to use the 69 90 again
single card gonna run at 16x 8x and 4x
PCIe bandwidth and see what kind of performance differences we see at 1080p
running in these games
so this was interesting uh not only did i test battlefield bad company 2 and
metro 2033 actually i've got my fraps one of my fraps results up here
right now oh apparently i have a lot of them up here right now okay so i also
added crisis 2 to the testing
methodology so here you go here are my results in a very tiny little graph that
i have made on a piece of paper along with a list of stuff that i had to do
the other day okay so here we are oh please focus come on you'll be kidding
me focus
focus there we go yeah yeah
okay so crisis two from 16x to 8x we're looking at pretty
much within margin of error but then as soon as we drop down to 4x PCIe
bandwidth we lose about six to well six
to eight FPS so that's going to be about 10 so we do see a tangible real world
performance decrease on a very high performance card in crisis 2 going down
to 4x that'll feel bad company 2 once again we see kind of within the margin
of error and then as soon as we go down to 4x we
see a very dramatic decrease in performance about 30
so metro 2033 same story this is margin of error right here and then moving down
to 4x we see a yeah 12-ish percent
performance drop so basically this goes
against the findings that i found before and i believe i know the reason so
running the extreme preset on 3d mark 11 basically meant that the
processors on the Radeon 6990 were completely taxed
so we were creating a processor bottleneck which meant that there didn't
have to be as much communication between the card and the rest of the system
because we weren't able to actually we were we were limited by how much
rendering these cores could do rather than by how quickly the card could
communicate with the system so running at 1080p with some modern games we were
able to create a scenario whereby the
card was not actually the bottleneck in the performance of the system in that
particular game so the processors were able to do more than the pci express
bandwidth was capable of communicating
so basically what we see here then
is that as soon as PCIe 3.0 comes out
we're probably looking at a scenario remember pci express is doubling in
bandwidth every time we see a new iteration but we're probably looking at a scenario where any modern card will
perform about like this at PCIe 3.0
4x and will perform about like this at PCIe PCIe 3.08 x and then there will be
a hypothetical probably like incremental 0.2 FPS beyond that so for any modern
card and remember this is two modern high-end gpus those are each 6970s on
there for any two modern high-end gpus
PCIe 8x is pretty much enough and 16x is
definitely enough based on how little improvement we see by doubling the
bandwidth from a PCIe 8x slot to a 16x slot so thank you for checking out this
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