PCI-E Lanes Question

[Lude2Envy]

I'm currently running the Z690 Extreme with one 3090Ti and one Samsung 990 Pro. I understand that my 14900K has 20 PCI-E lanes with 16 going to my GPU and 4 going to my m.2. My question is, if I add more m.2 drives, what happens to those PCI-E lanes? Are they further divided up. Do they start to mess with the bandwidth on my USB and Network ports? If not, how many more m.2 drives can I add before I start to notice issues with other devices? Thank you.

[Nate152]

Helo Lude2Envy

The ROG Maximus Z690 Extreme has three M.2 slots.

M.2_1 and M.2_2 use the cpu's pcie lanes. If you add an ssd to the M.2_2 slot, it will drop your gpu to x8.

M.2_3 uses the motherboard chipset lanes, you can add an ssd in the M.2_3 slot and keep your gpu at x16.

[Lude2Envy]

I don't believe that is correct about M.2_2 dropping GPU to x8. I have my 990 Pro in the M.2_2 slot right now since it's a Gen 4 drive. Even though the 3090Ti is Gen 4, I'm planning to purchase an Astral 5090 as soon as I can find one - which is Gen 5. If I remember correctly, the 12th/13th/14th gen Intel chips can't support both a Gen 5 GPU and a Gen 5 NVMe simultaneously because they only have 16 Gen 5 lanes. My GPU is currently running at 4.0 x16 and my 990 is running at 4.0 x4. If I add another 990 Pro to M.2_3, will that significantly affect my internet, USB devices, etc. if I run games off it, or will it be negligible? Is the speed/latency noticeably slower compared to the x4 drive? The DIMM.2 module runs off the chipset as well, correct?

[Nate152]

Ok, so you're using the M.2_2 slot for your ssd. As you say, you're already using the 20 pcie 4.0 lanes. If you populate the M.2_1 slot, this would drop your gpu to x8.

According to the manual, using the M.2_3 slot (chipset lanes) shouldn't affect any of your usb/sata devices.

The ssd that is connected with the cpu will always be a little faster in benchmarks, but from normal day to day use, you shouldn't notice any difference.

You should be able to add an ssd in M.2_3 along with your DIMM.2 card and still keep your gpu at x16.

[Lude2Envy]

I know the GPU will still stay at x16 with those slots used up, it was just the chipset bandwidth I wasn't sure about. You have a finite amount of bandwidth being shared with all of those devices on the chipset and I didn't know how much having SSDs on there as well would affect them - especially for online gaming since the ethernet runs through the chipset as well .

[Nate152 · Accepted solution]

True, but you have enough of chipset lanes to use M.2_3 and your DIMM.2 card, I don't see it affecting your internet at all.

You could always do a before and after internet speed test for peace of mind.