PCI EX16 Asus Tuf Gaming B650M-Plus issues with PCIe 5.0 compatibility and Gen5 functionality
PCI EX16 Asus Tuf Gaming B650M-Plus issues with PCIe 5.0 compatibility and Gen5 functionality
Hello, I've been using this motherboard for nearly three years and never noticed PCIe operating at 16x instead of 32x. Recently, I purchased a Zotac 5070Ti Solid SSF since my previous 3080 model is no longer functional and repairs seem unlikely. I performed some benchmarks and checked GPU-Z, which confirmed the x8 limitation. The Bus Interface in GPU-Z displays PCIe x16 5.0 at 4.0x speed (running render test), while Nvidia control panel lists system info as PCI Express x8 GEN4. I'm using a Ryzen 7600 with two NVMe drives—one at 4.0 and the other at 3.0—and both are functioning correctly at their expected PCIe speeds. However, when I installed a different GPU on my friend's MSI B550 Pro WiFi motherboard, it showed x16 3.0 at 8x. This suggests that regardless of the card, the interface defaults to x8. As far as I know, this board doesn't support lane sharing with M.2 devices, and PCI Express 16 uses x16 only with Ryzen 7000/9000 series processors. I searched online for solutions but didn’t find a clear answer. I located a BIOS setting for PCIe, specifically the PCIEX16_1 bandwidth configuration, which is intended for cards with M.2 drives inside. There’s no x16 option listed there, though it should exist if there’s no bifurcation. I discovered the PCIe link speed is set to GEN 4 in PCIEX16_1 Link Mode and M.2 link mode. The board supports a single M.2 GEN 5 drive, but PCIEX16_1 only offers GEN 4 at x16 according to ASUS specifications. I was unsure if it would work in GEN 5 mode, so I tried it anyway. It appears to be running at GEN 5 based on GPU-Z and HWinfo, though still at x8. While the GEN 5 feature is available, I remain doubtful about achieving true 16x performance. I’m relieved to see that GEN 5 support exists, but I’m still questioning whether it will actually deliver higher speeds. x8 5.0 is an improvement over x8 4.0, yet every card I’ve tested only reaches x8. I even removed the M.2_1 slot drive without changing results. What alternatives do I have left?
Initially, stay calm. There are several factors to take into account. Are you aware that the Bus Interface setting in GPU-z reflects the present interface speed? For instance, your system shows PCIe x16 4.0 at x16 Gen 1.1. This indicates your interface is configured for x16 Gen 4, yet it operates at x16 Gen 1.1 to conserve bandwidth or energy. Based on your screenshot, it appears your computer was set up for x16 Gen 5, but only used x8 Gen 5 at the time you captured it. Another point is that most GPU operations can function efficiently with x8 lanes. If a GPU has enough bandwidth through the PCIe x8 lanes, it’s unlikely it will ever switch to x16 mode. Keep in mind that x8 Gen 5 matches the bandwidth of x16 Gen 4 and x32 Gen 3 (assuming that existed). In short: if your GPU is working properly, you shouldn’t be concerned about the interface type. If performance drops (lower FPS, poor scores), check whether the interface mode might be affecting it. Have a great day!
GPU-Z offers a render test feature that activates the GPU in high state mode, displaying real performance data. Press the "?" next to Bus Interface and initiate the test. Your @x16 1.1 will update to your actual bus interface value. I attached the screenshot to suggest it was active at capture time. I also shared images of CPU-Z and HWinfo during the render test. The Nvidia Control Panel System Information consistently reflects the true interface. The issue isn't with PCIe Gen, but with the x8 limit. I tried a GTX 1070 which also showed x8 in my PC and a 5070Ti in MSI B550 that displayed x16. The problem lies not with the card itself, but with my motherboard. The x8 setting remains unchanged during the render test, confirming your observation. Others have noted the presence of PCIex16_1 Gen5 in their BIOS, though Gigabyte recently disabled it. Some report stable Gen5 performance. I checked CUDA-Z and found the host-to-device speed around 26 GiB/s, close to x8 Gen5 limits. This matches what you'd expect with x16 Gen4, but full Gen5 capability isn't confirmed with x8. To enable x16, consider checking if your motherboard supports it or updating BIOS to remove the restriction.
5070TI falls far short of fully utilizing an 8x PCIe Gen 5 slot. Performance gains won’t be apparent even when using lower speeds like 16x Gen 4 or 8x Gen 4. The card simply doesn’t provide sufficient data bandwidth for such configurations.
The generation adapts to lower loads, yet the lane count stays the same. Even if operating with 8 lanes when idle, it maintains 8 lanes during peak usage.
The issue isn't related to graphics card performance limits. It's connected to the motherboard.
Review your motherboard manual. Many budget mobos include their PCIe 16x physically, though they’re only wired for 8 lanes. This limits you to an 8x speed output. Such setups are typical in cheaper B series mobos. Some describe it as “PCIe x16 slot” while meaning a mechanical x16 connection, but others say it’s just an electrical x8 connection.
Hmm, seems like you might be mistaken about the main port. Most boards come with at least one full x16 slot, and the lower x16 is typically connected via x4 wiring.
You receive all the details mentioned. The labeling is unclear, making it difficult without consulting the manual. Some devices combine lanes with NVMe, and even premium models like GPU PCIe can be more affordable if you opt for a budget version. It's often cheaper to trace 16 lanes rather than 32.
I know the highest position can split, though no consumer boards exist that exclusively use the top slot at x8. Here’s an example: