Asus z690 Maximus Hero - Trying to understand best M.2 location

[mpoffo]

Sorry guys newer to this platform and I would appreciate if someone could confirm some things for me. I am use to a platform with more PCIe lanes. I just received my motherboard z690 Hero from Newegg (not a recall model). Anyway, I have a few questions about placement and options of the NVME as it relates to the PCIe slots.

If I am understanding things correctly for this board the top M.2 slot uses CPU lanes. So assuming I have a graphics card in the top PCIe slot that would take 16 CPU lanes. If I put a M.2 in the top slot on the board that would take up the 4 remaining CPU lanes, correct? In this config does this mean the 2nd PCIe slot on the mother board is inactive or does it use PCH lanes as well? In addition can the top M.2 two be changed to use PCH lanes vs CPU lanes?

If I put the M.2 in the 2nd or 3rd M.2 slot on the motherboard would that impact the performance of the drive for a Gen 4 WD SN850? I currently do not plan to use the M.2 expansion card.

Finally on a different topic, can I actively use the built HDMI port along side my graphics card to drive a secondary monitor? If so, will be impact performance or downgrade my graphics card to 8x speed instead of 16x?

Thanks for your help. It is greatly appreciated.

[xeromist]

Can't answer all of that but a few quick answers: You can't change from direct to chipset. It's the way the slot is wired.

My personal opinion is that you will not notice the difference running your SSD through the chipset. It will show up in synthetic benchmarks but unless you have a lot of devices sharing bandwidth on the chipset you won't ever "feel" it.

Using onboard video won't use additional lanes. The only performance concern is that the iGPU does generate heat so if you are overclocking that little bit of extra heat and power usage can cost you. Stock usage you won't notice.

[mpoffo]

Can't answer all of that but a few quick answers: You can't change from direct to chipset. It's the way the slot is wired.

My personal opinion is that you will not notice the difference running your SSD through the chipset. It will show up in synthetic benchmarks but unless you have a lot of devices sharing bandwidth on the chipset you won't ever "feel" it.

Using onboard video won't use additional lanes. The only performance concern is that the iGPU does generate heat so if you are overclocking that little bit of extra heat and power usage can cost you. Stock usage you won't notice.

Thanks very much xeromist. Your response was very helpful. In my current x299 rig I am using a secondary graphics card along with my 3090. I would like to get by with using just one. I have a 3 monitor set-up plus VR stuff (index). If the speed of the SSD won't be effected that much I might put in the 3rd M.2 slot for now. I am going to try using the onboard sound but have traditionally used a audio card.

The one remaining question I have is the one related to the Secondary PCIe slot if I use the top PCIe and M.2 slot for all 20 CPU lanes. What happens to the second PCIe slot in that instance? If anyone know that answer it would be appreciated.

[Silent Scone@ROG]

Hello,

As per the manual, M.2_1 supports CPU lanes. M.2_2 and 3 utilize chipset lanes. As per Xeromist's post, most drives won't saturate either and the difference will be negligible.

[Dezzmos]

The one remaining question I have is the one related to the Secondary PCIe slot if I use the top PCIe and M.2 slot for all 20 CPU lanes. What happens to the second PCIe slot in that instance? If anyone know that answer it would be appreciated.

Quite sure if you put something in your secondary PCIe slot the lanes will be split evenly between both slots (from 1x16 to 8x+8x).

[mpoffo]

Thanks for the follow-up replies. It is appreciated!

[Avaruuskettu]

Sorry for the late reply, just found this thread.

The one additional info missing from this discussion is that the PCIe lanes on the Z690 Hero are v5.0, and thus double the speed of 4.0, that is 32GT/s.

I have four M.2 SSDs in the PCIe 4.0 slots, two in motherboard's PCIe 4.0 x4 slots and two in the Hyper M.2 card in PCIe 4.0 slot (x4, x4), only the motherboard M.2_2 PCIe 3.0 slot is free.
AIDA64 reports that my GTX3080Ti is running PCIe 4.0 x16 mode. CPU-Z reports the same and current link speed of 16.0 GT/s.

I expected the mode to be PCIe 5.0 x8, but the speed is identical so I guess the motherboard can switch PCIe generation as needed?Â*

Current generation of graphics cards can't saturate PCIe 4.0 x16 so everything is working at max speed.Â*