Ryzen 4000 Mobile bottleneck concerns rise as PCIe is allegedly limited to 8x

[Djole123]

A slide from an internal AMD engineering team has surfaced courtesy of Igor's Lab showing that Renoir mobile CPUs may have a PCIe bandwith limit of just 4-8x, leaving a tight spot for GPUs like the RTX 2060S and higher.

 

 

Quote

AMD Renoir 'mobility' SoC utilizes only 8 PCIe 3.0 lanes for discrete graphics, could turn the tide towards Intel TGL-based gaming laptops in the high-end segment

 

Interestingly, this limitation does not apply to desktop (AM4-based) Renoir SOC as confirmed by Robert Hallock. The reason appears to be that while the AM4-based platform has access to 16 lanes of PCIe 3.0, the mobility platform is using a crippled version of the SoC for energy efficiency purposes and will only be able to utilize 8 lanes for a dedicated GPU. 

Although there still is enough headroom for mid tier GPUs, it is still a shame that it's stripped down when compared to desktop and Intel equivalents. Power users may still have to wait for either next gen Ryzens or just settle for an Intel CPU, albeit at a significant cost.

 

Source:

https://wccftech.com/amd-renoir-mobility-pcie-3-0-limited-to-8x-could-bottleneck-gpus-above-an-nvidia-rtx-2060-super/

https://www.igorslab.de/en/manufacturers-when-gaming-notebooks-in-the-clamp-ryzen-4000-apus-in-the-bandwidth-limit-tiger-lake-comes-first-with-only-4-cores-2/

[Master Disaster]

The 8 people in the world who would connect a 2060 Super to a mobile device should be expecting some kind of bottleneck, it's a very niche configuration. I don't see why this is an issue?

[Samfisher]

Are 4000 series laptop CPUs only using PCIE3?  Cos that image implies it.

 

EDIT:  Renoir is their desktop APU chips no?  They are based on the laptop chips but aren't made for laptops IIRC.

[Haro]

10 hours ago, Samfisher said:

Are 4000 series laptop CPUs only using PCIE3? 

yes they are iirc.

[WereCat]

I don't see an issue. x8 PCIe 3.0 is plenty for most graphics cards, there are another dedicated lanes for SATA and M.2, it's not like the x8 lanes are shared between everything. 

[leadeater]

PCIe 3.0 x8 will have a very minimal impact even on much higher end GPUs, 2060s will have no problems.

[givingtnt]

I am so very concerned about this insignificant limit of a mobile cpu having to deal with a larger gpu.

 

Stop calling affordable technologies with reasonable compromises bottlenecks.

[cj09beira]

igor is completely wrong here, when he claims this might be the reason we dont see high end gpus, the performance drop is minimal, still more pice lanes would have been useful for the desktop versions of renoir

[mr moose]

Do laptops even have big enough anything to make them a serious option for games?    I mean they are currently great at gaming,  however if you are looking for 2080ti performance on a g-sync 4K super extra large scale immersive 3d environment with cup holders are you really buying a laptop?

[5x5]

This is complete bullshit. The reason high end cards aren't paired with Renoir in laptops isn't PCIe, it's a brand contract intel have with OEMs that dictates their premium models with high end cards use exclusively intel. Think Geforce partner programme. It's the same thing. That's why no Strix laptop with AMD exists or why no Aorus laptop has AMD. Or why we don't see MSI G series. Lenovo and HP have a custom version of that programme due to their size and they still have low end Legion and Omen laptops with Renoir but no XPS or Spectre to make up for it. Igor is being very disingenuous by claiming the issue is PCIe

[5x5]

Despite what intel apparently said to linus on the record, mid level management is under a lot of stress due to mobile. They're closing ranks and from what I've been told off the record, next gen Intel is focusing hard on mobile and desktop is basically going to be a back port.

[leadeater]

2 minutes ago, 5x5 said:

Despite what intel apparently said to linus on the record, mid level management is under a lot of stress due to mobile. They're closing ranks and from what I've been told off the record, next gen Intel is focusing hard on mobile and desktop is basically going to be a back port.

Mobile/laptop is the largest market and the one they have the strongest hold on so would be the one to focus on.

[5x5]

3 minutes ago, leadeater said:

Mobile/laptop is the largest market and the one they have the strongest hold on so would be the one to focus on.

It's also the key to mindshare - that's why desktop is getting mostly left behind in favour of mobile, to quote, "by any means necessary". Server is big money but server adoption hinges on mobile popularity

[Sauron]

One minute people are on the thunderbolt eGPU train, the next they're calling a gen 3.0 8x slot a "bottleneck". Which is it, people? Where was this massive concern when Apple announced their pro laptops with a glaring lack of powerful dGPUs and people said "oh well you can just use thunderbolt"?

 

If 3.0 8x over 16x makes any difference at all here (which I highly doubt) it's going to be in the order of 1%, which is lower than the variance we typically see even between equally specced laptops with slightly different cooling and power profiles. Plus, realistically, the price is never going to be so close that a 1% difference in performance is what tips the scales.

[ThePD]

The only GPU currently that faces a bottleneck on PCIe 3.0 is a 2080ti and its by 2-3% when using 8x lanes.

[KaitouX]

First it was because they weren't prepared, then it was because AMD didn't give as much support as Intel so the process was longer, now it is because of PCI-E 3.0 x8. Also now that a laptop with a 115W 2060 exist there's no reason why you couldn't put a 2080 there without much effort, both would use the same amount of power anyway, and even if the performance wasn't good I really doubt that would be enough reason to not make the product at all, it wouldn't be that new for a more expensive product to perform not that different from a cheaper one, particularly in the notebook market.

In my opinion there's no GPU above the 2060 115W that makes sense on a laptop, as they're usually limited by the TDP anyway and aren't much faster so I don't care that much, but all excuses that are being made to not have higher end GPUs in Renoir Laptops is getting really annoying.

[Curufinwe_wins]

For now, fine. But if desktop has anything close to a similar limitation (perhaps due to sacrificing lanes by attaching the onboard gpu) I would be quite irrate honestly.

[Doobeedoo]

Meh really no concern about bottleneck there. 

[BabaGanuche]

This is not something to be worried about. It is 2 to percent with a desktop 2080 TI

[Djole123]

Edit: I just now realise the insignificance of the issue. It'll probably only affect like 3% of the Ryzen userbase.

 

I should probably stop reading Wccftech.

[cj09beira]

3 hours ago, Curufinwe_wins said:

For now, fine. But if desktop has anything close to a similar limitation (perhaps due to sacrificing lanes by attaching the onboard gpu) I would be quite irrate honestly.

desktop will be similar sadly, ou will be limited to x8 for the gpu, x4 for m.2 and x4 for the chipset.

with the last apu it was fine as it was quite weak but on this one its significant bottleneck

[CephDigital]

...Don't Intel mobile chips only have 8x PCIe 3.0 for their GPUs as well?

[schwellmo92]

The difference between PCI-E 3.0 x8 and x16 on a 2080 Ti is 3%.. as far as I know we don't have any mobile GPU's even close to a deskto 2080 Ti in terms of performance so having an x8 link is not a problem for mobile.

 

Source:
https://www.techpowerup.com/review/nvidia-geforce-rtx-2080-ti-pci-express-scaling/7.html

[Sauron]

17 hours ago, Curufinwe_wins said:

if desktop has anything close to a similar limitation (perhaps due to sacrificing lanes by attaching the onboard gpu) I would be quite irrate honestly.

It certainly won't... iGPUs don't use PCIE and, even if they did, x570 and b550 already offer plenty of lanes to account for that.

[cj09beira]

1 hour ago, VegetableStu said:

interesting update: the recent desktop Ryzen 4K APUs are full x16 o_o

 

thats great news thanks