AMD mobile GPU gets fewer PCIe lanes on desktop
In case you missed it, one of AMD’s board partners confirms desktop Navi 24 is limited to four lanes of PCI Express 4.0 interface
On the ASRock website, one can find pictures and detailed specifications of the Radeon RX 6500 XT, the latest member of the RDNA2 desktop GPU family. This card is based on the newest Navi 24 GPU manufactured using 6nm process technology.
As it turns out, this card has a PCI-Express interface limited to 4 lanes. Noted, this is a Gen4 interface, but this is still a shorter interface than its predecessor, the RX 5500 (XT) which offered a Gen4 x8 interface.
We gathered some pictures from the ASRock website showcasing how one can immediately notice how many lanes are electrically wired to the GPU. It is apparent that fewer lanes can be subsequently seen on the Navi 23 and Navi 24 based models:
ASRock confirms RX 6500 XT is PCIe Gen4 x4, Source: ASRock
With only four lanes available, the RX 6500 XT has the same 8GB/s bandwidth as PCIe 3.0 x8 or PCIe 2.0 x16 cards:
| PCI-Express Speeds | ||||||
|---|---|---|---|---|---|---|
| Generation | Year of Release | Data Transfer Rate | x1 | x4 | x8 | x16 |
| PCIe 1.0 | 2003 | 2.5 GT/s | 250 MB/s | 1 GB/s | 2 GB/s | 4.0 GB/s |
| PCIe 2.0 | 2007 | 5.0 GT/s | 500 MB/s | 2 GB/s | 4 GB/s | 8.0 GB/s |
| PCIe 3.0 | 2010 | 8.0 GT/s | 1 GB/s | 4 GB/s | 8 GB/s | 16 GB/s |
| PCIe 4.0 | 2017 | 16 GT/s | 2 GB/s | 8 GB/s | 16 GB/s | 32 GB/s |
| PCIe 5.0 | 2019 | 32 GT/s | 4 GB/s | 16 GB/s | 32 GB/s | 64 GB/s |
| PCIe 6.0 | 2021 | 64 GT/s | 8 GB/s | 32 GB/s | 64 GB/s | 128 GB/s |
The fact that RX 6500XT only comes with an x4 interface is not actually mentioned by AMD or big AIBs such as Gigabyte, ASUS, or MSI:
Neither AMD nor other AIBs list RX 6500 XT as PCIe Gen4 x4, Source: AMD/AIBs
What should also be mentioned is the fact that RX 6500XT is missing some important features from other RX 6000 cards, such as H264/HEVC encoding or AV1 decoding. All those missing features were put together by 3DCenter, who compare all Navi 2X GPUs:
AMD Navi 2X GPUs, Source: 3DCenter
Now the question is, does it really matter if the card has PCIe 4.0 x4 interface? In most cases, it won’t because this card was not designed for 1080p+ gaming. However, it should matter to gamers who will be looking at similarly priced models, such as Polaris RX570/580 or RDNA1 SKUs. In those cases, second-hand GPUs might be a better choice.
What is important to note is that RX 6500XT being a budget card may be paired by some gamers with older systems not equipped with PCIe 4.0 standard. In this case, the difference should be a lot more visible, because those systems will lack ResizableBar support.
