AMD Ryzen Mobile 4000 Discrete Graphics Limited to PCIe Gen3 x8

How Important is the PCIe Gen3 x8 Limitation?

Laptops featuring the Ryzen 4000 Series mobile processors have been, rather curiously, limited in the graphics department compared to similar Intel-powered systems. Even the signature configurations marketed toward gamers top out with an NVIDIA RTX 2060 at the high end (with the top all-AMD option sporting a Radeon RX 5600). No RTX 2070 or RTX 2080, Max-Q or otherwise.

And now we might have an idea as to why this is. Or maybe not.

AMD’s Ryzen 4000 Mobile CPUs are limited to 8 lanes of PCI Express 3.0 for discrete graphics. And if that information means anything to you, it should be apparent that AMD’s mobile Renoir platform (desktop offers x16) is rather limited in the PCI Express lane department. This information comes via VideoCardz (via Igor’s Lab).

But is this really a problem? Studies have been made about PCIe bandwidth scaling for GPUs, with TechPowerUp’s most recent in-depth foray conducted with an NVIDIA RTX 2080 Ti. The results shouldn’t be too surprising, as we are talking low single-digit percentages even with that mighty graphics card. And by low, I mean up to 3%.

Having just 8 total lanes of PCI Express 3.0 is not, after all, much of a factor in implementing a high-end graphics card in a laptop. Even so, it is a bit disappointing to see just x8 lanes of PCI Express 3.0 available to a discrete GPU in these systems, considering how impressive the CPU performance is – if indeed this lane issue has anything to do with the lack of available Ryzen 4000H-based machines with top-end graphics cards.

Thermals and power delivery are always the biggest hurdles with dGPUs in notebook designs, but advanced implementation and management techniques – not to mention big gaming laptops with powerful coolers and massive power bricks – exist to mitigate these. But for whatever reason we still don’t have a single Ryzen 4000 Series notebook option with a GPU higher than an RTX 2060.