discussion on pcie lanes
discussion on pcie lanes
Hi everyone, I have a query about my setup. I own a Gigabyte B650 gaming X-AX V2 motherboard with a Gen 5 NVMe slot and a Ryzen 5 7600 processor. I’m wondering if the second NVMe slot can support full Gen 4 speeds. I’ve listed all the PCIe and NVMe slots, and I’m curious if moving lanes between slots would affect performance. I’m also planning to add a Gen 4 NVMe in the first slot, another Gen 4 in the third, and use Gen 4 x1 cards in the last two slots. Thanks ahead!
These connections operate on PCIe Gen 3 x1, meaning you won’t receive maximum bandwidth with Gen 4 cards (though they should still function). For other equipment, performance should be normal based on the information in the manual.
Based on what I observe, the second M.2 port (M2B) accommodates PCIe 4.0 x4 connections. The processor provides 28 PCIe lanes, with 4 reserved for the chipset, leaving 24 available for other components. The graphics card can use up to 16 lanes, and each M.2 slot supports a maximum of 4. The third M.2 port along with the two lower PCIe (gen 3.0 x1) both draw from the chipset, meaning they share those four lanes. It’s unclear how they might conflict, but running them together likely limits overall performance.
If you populate all your slots like that there's a 90% chance SOMETHING is going to get disabled or gimped to a lower multiplier in the system, that happens with almost all modern boards because the CPUs only have so many lanes & even with higher end chipset boards (like the E-ones that have 2 chipsets on them) there's still compromises necessary to run a lot of devices at once. According to your manual... BOTH the lower PCIe x16 slots are only x1 PCIe 3.0 meaning they will lower the speed of any drive installed in them if you get cards to do so (I wouldn't bother with Gen4 drives, running a Gen4 Drive at Gen3 x1 speed is literally lowering it's potential performance by something like an 80-90% reduction.) Lucky for you, it doesn't say anything about any SATA ports or anything of the sort being disabled if a certain number of slots are occupied/NVMe devices are installed. I'm not seeing a mention anywhere of populating all 3 NVMe M.2 slots with drives resulting in a reduction in the primary PCIe x16 slot's performance. That's likely because the top M.2 slot is a Gen5 x4, the other 2 are Gen4 x4, the bottom one is through the chipset (so it'll be the slowest), the top Gen5 & Gen4 slots are both through the CPU... I honestly wouldn't be surprised if your GPU ends up in x8 mode... IF IT DOES that is not a big deal, the difference between PCIe Gen 4.0 x8 & x16 is pretty small on any GPU not called an RTX 4090, we're talking 1-3% difference in performance in games otherwise, on the 4090 it can be a LITTLE bit more.
This motherboard doesn't allow lowering the bandwidth for the PCIe x16 slot connected to the CPU.
The capture card supports PCIe x4 connections perfectly. When it operates on PCIe Gen 4, you may also utilize the Gen 4 M.2 port, while keeping the Gen 5 slot available for high-speed SSDs.