Graphic cards (Radeon Pro 5500M) suddenly PCIe lane changed from x16 to x8

[Hor Zheng Yi]

Im not sure if anyone encounter this, but yesterday I newly noticed that the PCIe lanes has changed from previous 'x16' to now 'x8' on Macbook Pro 16.

And I compared to bootcamp Win10 and macOS, they still read as PCIe x16, and mac is x8.

I have no idea why would Apple do that to slowing down our graphics performance, that's ****ing NOT acceptable.

 

[cheese01]

The "PCIe v4.0 x16" is what the GPU supports (according to https://videocardz.net/amd-radeon-rx-5500m, but the desktop equivalent RX 5500 XT only has 8 lanes, so who knows).
The Intel CPU only supports 16x PCIe v3.0 lanes (https://ark.intel.com/content/www/u...980hk-processor-16m-cache-up-to-5-00-ghz.html).

There are 16 lanes on the CPU, but not all of them are free to be used for the GPU. Most likely, 4 are being used for the SSD, and another 4 are being used for chipset/Thunderbolt, which leaves 8 lanes for the GPU.
Also note that the GPU might support PCIe 4, but Intel's CPU only supports PCIe 3.

The macOS information is correctly showing the PCIe lanes used to connect the GPU to the CPU in your MacBook, while the info from windows seems to just be looking up the GPU's specs from some external database, ignoring the details of the machine it's in.

 

[throAU]

The macOS information is correctly showing the PCIe lanes used to connect the GPU to the CPU in your MacBook, while the info from windows seems to just be looking up the GPU's specs from some external database, ignoring the details of the machine it's in.

I've seen gpu-z report both of my GPUs using 16 lanes in my desktop for example.

given I don't have 32 CPU lanes, this is BS. So yeah, the above is quite possible.

 

[Hor Zheng Yi]

The "PCIe v4.0 x16" is what the GPU supports (according to https://videocardz.net/amd-radeon-rx-5500m, but the desktop equivalent RX 5500 XT only has 8 lanes, so who knows).
The Intel CPU only supports 16x PCIe v3.0 lanes (https://ark.intel.com/content/www/u...980hk-processor-16m-cache-up-to-5-00-ghz.html).

There are 16 lanes on the CPU, but not all of them are free to be used for the GPU. Most likely, 4 are being used for the SSD, and another 4 are being used for chipset/Thunderbolt, which leaves 8 lanes for the GPU.
Also note that the GPU might support PCIe 4, but Intel's CPU only supports PCIe 3.

The macOS information is correctly showing the PCIe lanes used to connect the GPU to the CPU in your MacBook, while the info from windows seems to just be looking up the GPU's specs from some external database, ignoring the details of the machine it's in.

Alright. I understand that.
It's quite weird that before I update my mac OS Catalina 10.15.3, the PCIe lane was show as x16, after update to 10.15.5, it becomes x8.
That means the System info from mac app was 'show what GPU supports' just like Windows (before update), and after update, the system info has changed to graphics PCIe lanes that how many can use for support?