• Guest, The rules for the P & N subforum have been updated to prohibit "ad hominem" or personal attacks against other posters. See the full details in the post "Politics and News Rules & Guidelines."

How many PCIe lanes do dGPUs actually use, really?

whm1974

Diamond Member
Jul 24, 2016
8,539
1,401
96
I thing I have wondered about is just how PCIe lands does a Video Card really need, Such as my GTX 970? I have read that 8x PCI v3 lanes is plenty and then some for high end GPUs.

Can you get 970 performance out of x4 PCIe?
 

whm1974

Diamond Member
Jul 24, 2016
8,539
1,401
96
AnandTech actually did a great test of this a few years back. Now this was done with an HD7970, using PCI 3.0. But its still relevant.

https://www.anandtech.com/show/5458/the-radeon-hd-7970-reprise-pcie-bandwidth-overclocking-and-msaa

Provided you have PCI 3.0, and not 2.0 or older, it will most likely be fine. You will lose some frames, but not enough to be a major impact.
Thanks. The main purpose behind such such a video card is to make PCIe lanes available for other uses.
 

UsandThem

Super Moderator
May 4, 2000
11,365
1,908
136
Gamer's Nexus did the same test Anandtech did, but since it was more recent, the GPU used was a GTX 1080.

https://www.gamersnexus.net/guides/2488-pci-e-3-x8-vs-x16-performance-impact-on-gpus

But like Stuka87 showed with his link, nothing has really changed since then in that regard. As long as a person is using a PCIe 3.0 slot (and at 8x and above), there's really no difference. In fact, I ran my GTX 1080ti at 8x for around 6 months while doing Folding@Home, and there was literally an insignificant difference.
 

whm1974

Diamond Member
Jul 24, 2016
8,539
1,401
96
Given that NVMe SSDs are becoming cheap enough to replace SATA SSD, I wonder if we will see midrange/high end dGPUs that are wired to x8 PCIe to make more lanes available for high speed storage?
 

PrincessFrosty

Platinum Member
Feb 13, 2008
2,301
68
91
www.frostyhacks.blogspot.com
Given that NVMe SSDs are becoming cheap enough to replace SATA SSD, I wonder if we will see midrange/high end dGPUs that are wired to x8 PCIe to make more lanes available for high speed storage?
The demand on PCI lanes comes from the bandwidth the GPU needs to communicate with the CPU/Memory, that's basically proportional to the speed the GPU and fill and uses it's memory, so as video cards get faster they'll have a greater overhead on PCIe although right now it looks like the impact of bottlenecking PCIe is very small. You can run most high end video cards in 8x mode and get basically the same frame rates.

Really these features need to come from the motherboard, get a motherboard that can allocate lanes of PCIe through the BIOS, that means limiting the x16 slots to x8 and then freeing up alternative PCI x8 or x16 slots

Main thing at the moment is that NVMe drives are not great upgrades for gamers, the additional data rate is only helpful in a very small number of circumstances. Almost no games load faster because of NVMe over SATA, I have 2x 960 Pro's in RAID 0. The biggest benefit I've seen so far is smoothness in loading in game assets in open world games, most notably Subnautica where a lot of people suffer extreme lag as the engine streams in new biomes as you traverse the map.

I do know as games start to move towards 4k appropriate textures and huge open world we're starting to look at games in the 100Gb+ size range and even larger in future, faster drives, faster PCIe and more memory is going to be important. Many games today still use absolutely hideously small textures, the ones from the 4k pack for R6 Siege are a good example of textures done right, but the install for the game is 116Gb for me. I'd love to see similar levels of detail for other modern AAA games, especially some of the open world ones.
 

whm1974

Diamond Member
Jul 24, 2016
8,539
1,401
96
I was assuming that with AAA games going to 4K or even 5k resulotions that such games will have much larger assets that load times would benefit from using at least 2x PCIe NVMe storage devices.

Of course that will also depend on wither or not mainstream games jump on 4k or 5k displays in large numbers anytime soon.
 

Stuka87

Diamond Member
Dec 10, 2010
4,320
337
126
With PCIe 4.0 around the corner, 4.0 8x will be faster than 3.0 16x. There won't be a need for 16x for a GPU. At least not in the near term.
 

ASK THE COMMUNITY

TRENDING THREADS