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View Full Version : Rog Strix Z590-F and PCIe4.0 lanes usage with GPU, and 2xM.2 PCIE4.0?



Nitrius
03-24-2021, 11:19 PM
It says in the specs that both M.2_1 and M.2_2 supports PCIe4.0 x4, but how does this work if you use both with 2x 1TB Samsung 980 Pro, and also got a RTX 3080? Will the GPU have to run at x8 instead of x16? Or will something have to run at PCIe3.0? If so, which part?

Running the GPU at PCIE4.0x8 or 3.0x16 should matter much after my readings, so that's okay, but if the nvme's have to run PCIe3.0 that would limit them from hitting the advertised speeds won't it?

The parts would be:
Asus Rog Strix Z590-F
Intel 11900K
Nvidia RTX 3080
2x 1TB Samsung 980 Pro

In short, will there be some limitations on the motherboard with this, if yes, where?

Zardoc
03-24-2021, 11:25 PM
Hi,

Only one lane supports PCIe 4.0 and that's with 11th gen CPU.

From manual
IIntel 11th & 10th Gen Processors
3 x PCIe 4.0/3.0 x16 slot(s)*
- Intel 11th Core processors support PCIe 4.0 x16 or x8/x4/x4 mode(s)
- Intel 10th processors support PCIe 3.0 x16 or x8/x4/x4 mode(s)

Total supports 3 x M.2 slots and 6 x SATA 6Gb/s ports
Intel 11th Gen Processors
M.2_1 slot (Key M), type 2242/2260/2280/22110
- Only Intel 11th Core processors support PCIe 4.0 x4 mode, this slot
will be disabled for other CPUs

the Z590 Chipset does not house any PCIe 4.0 lanes. Instead it has the same 24 PCIe 3.0 lanes as seen on its Z490 predecessor.
In addition it can redirect the 11th Gen Intel CORE CPU 20 PCIe 4.0 lanes to some of the board components ( on this board, a PCIe 16 export slot and M.2 SSD connector).

with a 11th GEN Intel CORE CPU, your board can now support up-to 3 M.2 SSDs, 1 of which can transfer data at PCIe 4.0 bandwidth levels, meaning up to a whooping 64 Gbs.

Nitrius
03-25-2021, 09:17 AM
Thanks for the answer.

I was of the understanding that both M.2_1 and M.2_2 should support PCIE4.0 according to specs, but that M.2_2 might share bandwidth with the PCIEx16 slot, so if i hook everything up the PCIEx16 slot will run at x8 instead?

Anyway, how much speed reduction will the SSD Samsung 980 Pro get if its running in PCIe3.0 mode and not 4.0? or is PCIE3.0 enough for the 7000/5000 MB/s that the drives are specced for?

Zardoc
03-25-2021, 02:26 PM
Hi,

I might be mistaken but if you use M.2_1 and first PCIE X16, there should not be a speed reduction because each lane is run by the CPU. The other lanes are run by the chipset @ 3.0.

I don't know what the speed reduction is at 3.0 but I imagine a 1/4 less around 2500 or so but it's a guess.

Nitrius
03-25-2021, 06:12 PM
According to specs on the Asus Z590 boards there is a lot of differences. Comparing Strix Z590-A with Z590-E for example, where the last one got more M.2 slots than the first, 3 vs 4.

On the Asus Rog Strix Z590-F board it's said that both the M.2_1 and M.2_2 support PCIe4.0, and to my understanding both will run that if you use them, but in conjunction with a PCIE4.0 GPU, the x16 slot will be reduced to x8 because there is not enough lanes for x16 GPU and 2x4PCIE4.0.

Though I opted on returning my two 1TB Samsung 980 Pro drives for one 2TB Samsung 980 Pro instead, just to be on the safe side.