PCI-Express Bifurcation

PCI-Express bifurcation is a system's ability to split a x16 PCIe lane configuration into smaller segments to run several devices independently on that single slot. From a technical perspective, the ASUS card is really one PCIe x8 device (the GPU) and a second PCIe x4 device (the M.2 slot for the SSD). The signals are routed straight through from the motherboard slot, there is no bridge, splitters or redrivers sitting in the link. In theory, and if cost didn't matter, ASUS could have added a PCIe bridge chip on their card, which handles the lane distribution, which would ensure the M.2 slot works on all motherboards, even ones without bifurcation support.

Bifurcation is a setting available in your motherboard BIOS, also using names such as "CPU PCIe Configuration Mode," or "PCIe Lanes Configuration." I've tested this on a couple of motherboards.


First, the ASUS Z790 Dark Hero, released just weeks ago. Here we see the option, but it only has two entries: x16 or x8/x8. The x8/x8 switches eight lanes from the 1st PCIe slot to the second PCIe slot. With this motherboard you can not use the SSD on the RTX 4060 Ti.


Next, the ASUS Z590 Maximus XII Hero (released in 2021). Here the option uses the same title like on the Z790 board, but there's a third option "Hyper M.2 x16." This is exactly the setting we need, because it enables the right mode that we want, giving x8 to the GPU and x4 to the SSD, both connected to the same slot.


I also tested the ASUS X670E Hero, for AMD Socket AM5, which properly identifies the option as "bifurcation," making it easier to find. Here we get three options, too, but this time the right one is called "PCIe RAID Mode," but the explanation on the bottom confirms that this is the same as the "Hyper M.2" option that we saw on the Z590 board. I've tested it, the M.2 SSD in the board is detected and working great.


Last but not least, I took a look at the highly affordable Ryzen AM4-based MSI X570-A Pro motherboard. Here the option is labeled "Lanes Configuration," and it very clearly identifies the options. You want "x8+x4+x4" for this card, activating "x4+x4+x4+x4" will work, too, but the GPU will run at only four lanes instead of eight, which will cost some performance.

M.2 Performance Testing

As mentioned before, the SSD slot on the ASUS RTX 4060 Ti Dual M.2 is connected directly to the motherboard's PCI-Express slot—there is no PCIe bridge chip. This means that bifurcation support is required from the CPU, motherboard and BIOS.


On this page we're showing storage performance results of the PCI-Express 4 Samsung 990 Pro and PCI-Express 5 Corsair MP700 Pro. While the RTX 4060 Ti GPU supports only PCIe Gen 4, it is perfectly possible to install a Gen 5 SSD in the graphics card, and it will run at Gen 5 speeds (as long as your CPU supports it). This is possible because the lanes are separated and can be configured independently.

PCI-Express 4.0 Performance

For our first round of SSD performance testing we'll be using a Samsung 990 Pro, which is pretty much the fastest high-end Gen 4 SSD available on the market. Testing on this page is conducted with an AMD AM5 platform (unlike the rest of the testing in this review, which is done on Intel).

We'll be testing:

• SSD installed in the M.2 slot on the ASUS RTX 4060 Ti
• SSD installed in the M.2 slot on the motherboard closest to the CPU (between CPU and x16 PCIe slot)
• SSD installed in the the second x16 PCIe slot, using a riser card
• SSD installed in an M.2 slot on the motherboard that's connected to the chipset (not the CPU)

This will give us a good feel for what to expect performance-wise, and whether there's any compromises to be made with the ASUS RTX 4060 Ti's M.2 solution.



Very impressive numbers—the ASUS M.2 addon doesn't cost any performance. Actually, it looks like random read is a little bit faster when using the SSD in the RTX 4060 Ti. The results from the riser card in the x16 slot confirm these numbers, so it seems that these two PCIe interfaces are a little bit quicker, no idea why. As expected, the connection through the chipset interface is a little bit slower, but not by a huge amount.

PCI-Express 5.0 Performance

Many of you will be wondering "what about Gen 5 SSD support?" This is a great question, because the RTX 4060 Ti is a PCI-Express 4.0 GPU, so wouldn't it be logical that SSD support is constrained to Gen 4, too? No, due to the way bifurcation works, the two virtual PCIe ports are completely independent, and the M.2 slot will run at Gen 5 as long as Gen 5 is supported on the CPU/motherboard/BIOS.


(typo, this is actually MP700 Pro)



Impressive results, and here, too, we see a performance boost when the SSD is running in the ASUS card's M.2 slot.

M.2 Temperatures

Temperatures are generally a non-issue, even with a Gen 5 drive running at full speed. The FLIR thermal imaging shot above shows just 53 °C, which is barely warm for a modern SSD. It really helps that ASUS is using a reversed slot, which makes sure the heat goes into the main heatsink of the GPU (on the other side).