z790 Lanes

[Dakota1]

I just built a new Comp with z790  Dark Hero.  I put a Crucial T700 in M2_1 and set it to gen5 in bios.  I put rtx 4090 into Pcie slot 1 expecting to get X8 lanes rather than the 16 max.  But I'm only getting 4 lanes on my Pcie slot with 4090.  I have no sata drives connected.  Samsung990 pro in M2_5 (boot drive) , the other three nvme populated with Western Digital Black.  I've checked bios but can't find a setting that will change this.  I expected to lose 8 lanes by populating nvme2_1 but not 12 lanes.  Any help????

[Jiaszzz_ROG · Accepted solution]

Hello, @Dakota1 

May I ask when this issue occurred and if it happened after any specific software or hardware changes, such as a BIOS update or the installation of a new GPU? Is the current 4090 installed in PCIEX16(G5)_1?
If you remove the SSD occupying m.2_1 and clear CMOS, is the GPU able to operate at x8 or x16 speed?
Could you please provide the following information to help us better understand your specifications?
- the images of all the manual setting in BIOS
- the brand and model name of the CPU, RAM (part numebr as well), SSD/HDD, and PSU currently installed
- are there any extensions or adapters used to connect any devices, such as GPU or SSD?
- the OS version and OS build

Thank you.

[Dakota1]

I actually found the problem today.  I had done a lot of research on the Pcie gen 4 and 5, but didn't realize the riser for gen three was different than the riser for gen 4.  I bought a Gen 4 riser and got the 8 lanes.  Wish intel had designed a little different.  Coming from a x299 with 48 cpu-pcie lanes this feels a little cramped.  lol.  

[Jiaszzz_ROG]

Hello, @Dakota1 

I'm glad you were able to pinpoint the problem.
If you encounter any further difficulties or have any concerns, please feel free to start another discussion thread or PM me anytime.

Thank you.