ASUS ROG Crosshair X870E Dark Hero ATX Motherboard

In December 2025, I purchased an ASUS ROG Crosshair X870E Hero ATX Motherboard from Amazon that couldn't get through the POST without failing. Despite the fact that I was able to confirm that every other component worked in a different MB, I didn't receive a Refund until 04-06-2026. ASUS wanted to send me a Remanufactured MB as a replacement and Amazon fought me for 3 months before finally complying with a full Refund. The secret to success was repeatedly calling back until I got someone who would cooperate.

Obviously, I'm not pleased with either ASUS or Amazon. I wasn't pleased that the Hero only had a 5GB Internet chip. For the price of the MB it should have had a 10GB chip. I figured I could live with it, but now I'm having second thoughts as it will be used primarily for Gaming. The new Dark Hero version has a 10GB chip for "only" an additional $100!

The Manual for the Dark Hero is as clear as mud regarding Lane Sharing. It appears that to keep the Graphics Card running at PCIE 5.0 x16 I can only use a single M.2 5.0 NVME slot. It appears that adding a second M.2 will degrade the Graphics Card to x8 and also reduce the NVMEs to 4.0... I'm fighting a nasty virus and my brain is not 100% right now, but that's what I think the Manual is saying.

Is there a MB out there that will allow even a single PCIe5.0x16 to run at x16 with *two* M.2 NVMEs running at 5.0? I've always run at least two internal storage drives, and I'd really like to retain that capability.

Thanks for any thoughts...

This is a genuinely thorny lane-allocation problem, and the short answer is: not really on any current consumer platform

dealpapa said:

This is a genuinely thorny lane-allocation problem, and the short answer is: not really on any current consumer platform

Click to expand...

Thanks for the Confirmation!

Looking at the motherboard specifications shows you the branching points.

For the ROG CROSSHAIR X870E DARK HERO, slot 1 PCIe 5.0 x16 does not share a lane with the M.2_1 and M.2_2 ports:
"** When PCIEX16_1 runs at PCIe 5.0 x16, PCIEX16_2 will run at PCIe 3.0 x4. The bandwidth can be altered in the BIOS."

M.2_2 port shares lane with USB4 40Gbps ports:
"* The USB4 40Gbps ports and the M.2 Socket 3 slot (M.2_2) share the available bandwidth. When a device is installed in the M.2_2 slot, both the USB4 controller and the M.2_2 slot operate at up to x2 mode. By configuring the M.2_2 slot in the BIOS, the M.2_2 slot can operate at up to x4 mode. However, enabling this setting will disable the USB4® 40Gbps ports."

itsme1 said:

Looking at the motherboard specifications shows you the branching points.

For the ROG CROSSHAIR X870E DARK HERO, slot 1 PCIe 5.0 x16 does not share a lane with the M.2_1 and M.2_2 ports:
"** When PCIEX16_1 runs at PCIe 5.0 x16, PCIEX16_2 will run at PCIe 3.0 x4. The bandwidth can be altered in the BIOS."

M.2_2 port shares lane with USB4 40Gbps ports:
"* The USB4 40Gbps ports and the slot 1(M.2_2) share the available bandwidth. When a device is installed in the M.2_2 slot, both the USB4 controller and the M.2_2 slot operate at up to x2 mode. By configuring the M.2_2 slot in the BIOS, the M.2_2 slot can operate at up to x4 mode. However, enabling this setting will disable the USB4® 40Gbps ports."

ROG CROSSHAIR X870E DARK HERO | ROG Crosshair | Gaming Motherboards｜ROG - Republic of Gamers｜ROG Global

The ROG Crosshair X870E Dark Hero is ready for Advanced AI PC. It makes builds soar with 20+2+2 power stages, hyper speed DDR5 support and the latest PCIe® 5.0

rog.asus.com

Click to expand...

OK, I *think* I've got it.
Graphics Card installed in PCIe slot 1 will operate at 5.0 x16
Capture Card installed in PCIe slot 2 will operate at 5.0 x4
M.2_1 slot can operate at it's max possible rate, x4 mode with my 4TB NVME

And if I disable *both* of the USB4® 40Gbps rear ports via the BIOS:
M.2_2 slot can now operate in it's max possible x4 rate with my 8TB NVME

Please confirm, and thanks GREATLY for the info!

Capture Card installed in PCIe slot 2 will operate at 3.0 x4
The rest is fine.

itsme1 said:

Capture Card installed in PCIe slot 2 will operate at 3.0 x4
The rest is fine.

Click to expand...

OK. Again thanks muchly - I can live with that. I don't foresee a need for the two USB4 40Gbps ports, and I believe 3.0 x4 will be adequate for the Capture Card. If not, then an External Capture Card is an option with the highest speed USB3 port. I think running the GPU PCIe at 5.0 x8 would have no effect on Captures...

Okay. If you look at other motherboards, the branching points will always be indicated in the specifications for the brands Asus, Gigabyte, MSI, and ASRock.