NVIDIA RTX 4090 PCIe 3.0 vs. 4.0 x16 & '5.0' Scaling Benchmarks

[Music] today we're doing pcie bandwidth testing so we're looking at the generational impact on the RTX 4090 when you use pcie gen 3 versus pcie gen 4. technically we also ran it with the motherboard set to Gen 5 but generation 5 pcie is not supported by the RTX 490 so it doesn't do anything we threw it in there anyway though because we knew people would ask so really this is three versus four there's a little bit more Nuance to this where you can start to derive some usefulness when you also scale eight Lanes versus 16 lanes for example between the two because pcie gen 4x8 is the same as pciegen 3x16 for the most part they're about the same bandwidth so let's get into the testing today it's gonna be a really simple one and we'll see how it scales before that this video is brought to you by montex Sky one light PC case the sky one light is montec's high airflow case with ventilated front panel included fans and RGB LED accents this guy one light is a compact mid tower case for ATX build and the argb LED quick connect on the front panel makes it easy to maintain the case without all the cables dust filters are strategically placed and there's basic cable management features while still maintaining a competitive price learn more at the link in the description below first up some backgrounds we did a lot of test passes here normally we do a minimum of four and then we multiply that depending on sort of the level of accuracy we need and you're looking at the same device and you're only changing the pcie generation there's a possibility that you run the numbers really close together and need that extra set of sort of accuracy or data resolution to get the numbers that you want to actually get to be able to say this is a real difference and not just variants so we did more test passes than normally now pcie specs there's a couple of layers of support that have to happen and when you're talking about pcie generational versioning for uh there's vaseline on this card for which motherboard basically to drop it into at a at sort of the lowest possible end really what you care about is the realized performance or the actual in-game or rendering performance or whatever it may be because the theoretical maximum throughput is different from the actualized throughput so you have to have support for the pcie generation you want to use at the CPU level if you look at a CPU block diagram for example and then it's got to pull maybe 16 lanes for example down to Peg 1 which is the first pcie slot typically uh for graphic support and that's how your Generations dictated at the CPU and the platform level that'd be the motherboard if you're running lanes that are fed from the chipset which is uncommon these days but possible for NVIDIA you need by eight so you need eight Lanes can't do it on by four officially anyway and those eight lanes are probably going to be a lower generation of pcie than what you're getting off the CPU plus you've got DMI or a additional overhead basically between the CPU and the chipset anyway but this is a relatively uncommon thing so we're not going to be testing for that because Crossfire and SLI are dead not even basically just actually the final layer of support is the video card has to support it so Nvidia is RTX 4090 is on pcie gen 4. now this isn't actually necessarily a bad thing if the card cannot utilize pcie Gen 5 in a meaningful way so remember with interfaces and protocols you're typically limited by the device before the interface itself unless you're running a much newer device on a much older interface a great example of this would be back when SATA hard drives were the fastest thing you could get ssds weren't out yet and you might cap out at maybe say 200 megabytes per second or whatever for a particular year of hard drive while the interface itself could run closer to 550. so the interface was never a concern up until the devices got fast enough obviously and that's true for pcie as well where gen five maybe it doesn't really matter for this we won't really know formally but we can get a good idea for how much gen 3 versus Gen 4 matters so that's the theoretical speed side of things versus actualized and we can test theoretical we'll show you that and then the last thing to know is that pcie generation becomes a lot more relevant on devices where they decide to cut down the lane count to say by eight so if you're running eight Lanes to say an arc a 580 or whatever it was it's not out yet we're running eight Lanes to an AMD 6500 XT now if you go from pcie Gen 4 to pcie gen 3x8 you are really limiting your maximum possible throughput both theoretical and actualized shown in test data we've published in the past where you're because pcie Gen4 buy it versus PCI you done three by is a 2X change that's where you start to really lose on performance uh that in this case it won't matter because it's all by 16 uh gen 4. here's a quick image just to show you the max theoretical bandwidth to get everyone up to speed so technically pcie gen 7 is planned for 2025 ratification that doesn't mean you'll see it on boards necessarily probably you'll start to see at least rumors of it but that's the plan Gen 6 is introduced I think it's been ratified or at least parts of it have been ratified but it's not on boards yet and then Gen 5 which was introduced in 2019 is now on board so if you look at the transfer rate per Lane uh or actually it's even easier if you look at the throughput per Wikipedia by 16 Gen 5 can go approaching 64 gigabytes per second gen 4 by 16 is about 32 gigabytes per second you see it's a pretty clean having you go down to gen 3 you're at 16 gigabytes per second so that is the theoretical Max throughput of the inner face itself whether or not the card utilizes that depends on the card okay let's get into the first set of tasks this one is the pcie bandwidth test so using the 3D Mark pcie bandwidth test we're able to rapidly determine the maximum theoretical throughput of the pcie slot and this will not necessarily materialize an equivalent deltas and gaming or real applications unless they directly mirror this synthetic workload but we haven't encountered anything that behaves the same way as the bandwidth test does in real life doesn't mean it's not out there just means we're not aware of it and if you are please tell us what that is so we can test it next time here's the chart with the motherboard configured to Gen 5 the results is the same as Gen 4 that's because the card doesn't support pcie gen 5. the maximum theoretical throughput is 25 and a half gigabytes per second here with the Gen 3 result dropping nearly in half to 13 gigabytes per second you can see there's some overhead there because actual gen 3x16 to be closer to 16 gigabytes per second gen 2 drops another half down to 6.7 gigabytes per second and these results make sense and they align roughly with some overhead with the spec for pcie the most important thing with this test other than just showing you that yes theoretically you can produce a difference is that the toggle we're using in BIOS works so that's important so the way to test for this type of thing without switching the whole rest of the system which would invalidate the test and it's basically to use built-in toggles in BIOS to drop down the pcie generation This Test shows that those locks are in fact functioning properly and it's not just for show so it tells us that the testing approach we're taking is accurate all right let's get into the gaming result so total Warhammer gives us a heavy load with dx11 which isn't as close to the metal the pcie Gen 4 results ran at 124.9 so 125.4 FPS average with Gen 3 at 122.5 average now top to bottom that's a maximum theoretical advantage of 2.4 percent on Gen 4 and variance is about 0.5 percent here 14 1840p is more interesting here are the best result was 236.6 FPS average with the worst at 227.4 FPS average on pcie gen 3. the best result leads pcie gen 3 by 4 with the original test data it's just another set of passes mind you but conducted a week earlier leading at 3.6 percent so that's more noteworthy than we saw at 4K 1080p widens that Gap to a really interesting extreme in this one we saw the pcie Gen 4 result placing at 315 to 318 FPS average that's reasonable variance at this frame rate the pcie Gen 3 result though was outside of variants at 277 FPS average that allows the Gen 4 results a massive lead comparatively of about 15 percent to a point where it's actually a big chunk of the GPS maximum performance and also a gigantic red flag to us that we need to retest so we re-ran these tests on two different test benches that are identical for performance and ultimately we confirmed the find it as a sanity check and because it's good lab practice we called Nvidia and requested that it have its own performance Lab look into the results it's currently cued to do so and we're waiting for those to come back for now though the best guess that GN and nvidia's team member just sort of unofficially have is that we found potentially a hole in driver optimization it may be a pcie bandwidth Behavior but it's probably more likely that this is a combination of the pcie bandwidth with driver Behavior regardless this is an outlier but it's an interesting one we'd have to test probably hundreds of games to reliably find more of these types of results it's something that could happen it's just there's no real predictable way to make it happen shadow of the Tomb Raider is next at 4K this had us at 202 FPS hours with Gen 4 that validated on both sets of stock passes the pcie Gen 3 result dropped to 198 FPS average allowing a maximum advantage of 1.7 percent on pcie gen 4. in the very least the consistency of lows here is impressive we're feeling good about our testing methodology at this point given the tightness of those results but for pcie Generation differences it's not that exciting at 1440p we're seeing similar results the two gen 4 tests ran at 241 to 242 FPS average with a maximum advantage of 0.5 percent that's variance so it's irrelevant the lows are within variants as well Final Fantasy 14 at 4K produced a range of 214 to 215 FPS average on Gen 4 results with Gen 3 at 208 so there's a maximum Improvement in this set of tasks so 3.3 percent Rainbow Six Siege at 4K and on dx11 ran at 355 to 356 FPS average with Gen 4 data sets even with a week between the tests and gen 3 ran at 350 FPS average that's outside the expected variance which is actually really small in this game as indicated by the bars and the maximum uplift is one and a half percent at 1440p technically the range widened here but not a meaningful amount versus the one and a half percent result preview obviously we're at 1.96 maximum uplifting out and at 1080p we're seeing less than a one percent swing and Rainbow Six Siege but we're also running 1080p on an RTX 4090 so that's part of why we threw strange Brigade in here using Vulcan at 1080p as well just to throw another extreme into the mix of a different API at a low resolution just to see if any unique behaviors emerged they didn't the maximum Delta we observed was 1.3 percent so that's it for the piece that you bandwidth test and this is pretty much the same we see every generation where with the newest card on the newest version of pcae versus the previous version it's about a one to three percent range so that's what we're seeing there is one really unique and interesting outlier and that was total Warhammer 3 where at 1080p specifically and only for that bench and with the settings we use with DirectX 11 with the battle Benchmark we saw a 15 range and that was reproducible multiple times with two different test benches and then we also call them video this sort of set in motion a perform lab evaluation of it to try and get an answer for why that's specifically happening and when we get that answer we'll put it in a hardware news that's just an update for educational purposes of okay this is a behavior but why that though is truly an outlier and like we said earlier you'd have to test hundreds of games to really find those and start to establish a pattern for when they happen so overall you don't need to worry about pcie bandwidth too much here it's a couple percent range maximally and realistically if you're spending 1600 on a video card not too many of you although there will be some will be slotting that card into an old enough system that it's Max pcie support is Gen 3. so for the most part kind of a non-issue but if you're looking at say a buy eight gen for interface you can compare those results to by 16 gen 3 and you're looking at a one to four percent range or so maybe with occasional outliers that we can't really account for but um that's it it's it's very simple and straightforward for this one check back for more as always go to store.gamersaccess.net to help us out directly and we have more follow-up testing we're doing on the CPUs and the GPS that all just came out uh those follow-ups a lot of them will be shorter like this one and very focused on just strictly what we're talking about for the follow-up so subscribe for more we'll see you all next time

Channel: Gamers Nexus

Views: 400,191

Keywords: gamersnexus, gamers nexus, computer hardware, pcie 4.0 vs 3.0, pcie 4.0 x8 vs 4.0 x16 rtx 4090, pcie 5.0 vs 4.0, pcie bandwidth scaling rtx 4090

Id: v2SuyiHs-O4

Length: 13min 9sec (789 seconds)

Published: Mon Oct 31 2022

Reddit Comments

[u/ListenBeforeSpeaking]

The nice part about 5.0 support would have been the same bandwidth in half the lanes, allowing us to free up another 8 lanes for whatever we choose.

That being said, it doesn’t look like we lose a ton with 8 lanes.

[u/PapaBePreachin]

Video description via GN:

This testing is for PCIe generations on the NVIDIA RTX 4090 GPU. We're benchmarking PCIe 3.0 x16 vs. PCIe 4.0 x16 vs. PCIe "5.0" x16 (but the 4090 doesn't support 5.0, so it's just 4.0 -- still worth showing for educational purposes). Remember that PCIe 3.0 x16 is equal to PCIe 4.0 x8, so if you're wondering if the RTX 4090 behaves differently on PCIe 4.0 x8 vs. x16, these two tests would answer that.

We're doing testing on an Intel i7-12700KF, which is Gen5-ready but again, if the device isn't Gen5, that doesn't matter. If you're wondering about AMD vs. Intel for the RTX 4090, strictly from a PCIe standpoint, it doesn't matter at this point -- they're the same in that regard. Other factors are more important, like CPU performance in the applications you run (see our CPU reviews for that).

One correction of an off-hand remark at 4 minutes 25 seconds - the RX 6500 XT has 4 PCIe lanes (Gen4), not 8. We forgot how much of a piece of trash that card was, sorry. Our mistake for not double-checking.

[u/inyue]

Well I have a faulty z690 mobo from gigabyte that does only PCIe 3.0. Guess I'm fine for a while if all I do is gaming?

[u/TheBCWonder]

Did a GPU finally saturate a PCIe 3.0 x16?

[u/LiKenun]

If Nvidia made this a PCIe 5.0 x8 card, I’d buy. Given the scarcity of lanes on even the high-end PCIe 5.0 motherboards, and the market this GPU is for, having it occupy 16 PCIe lanes running at half speed is plain stupid.

[u/b-macc]

My 4090 was stuck at x16 1.1 after my initial install on a MSI b650m mortar and a 7700X. My scores were 20 to 30 percent lower in 3D mark than the average 4090. Luckily there was a bios update that fixed the issue and I am running at x16 4.0 and scores are similar to other 4090s now.

[u/KingStannis2020]

If I have two NVMe SSDs where one uses PCI-e 3.0 and one uses PCI-e 4.0, does the system get locked to PCI-e 3.0 (the lowest common denominator) or do the various devices co-exist with their corresponding protocol support?

[u/Jeep-Eep]

So this is pushing me to the 5800x3d as an upgrade, as it won't be hindered by lacking 4.0?

[u/Vitosi4ek]

So, barring one outlier that is probably related more to driver optimization than PCI-E bandwidth limitations, the FPS in real games barely changes when moving down from Gen4 to Gen3.

This means that even the absolute fastest GPU today, in late 2022, cannot fully saturate an interconnect rolled out in 2010. This, if anything, makes me wonder if PCI-SIG develops new standards a bit too quickly - it's not necessarily bad as long as they remain fully backwards compatible, but there's still barely any Gen4 gear that actually utilizes the increased bandwidth, much less Gen5.