Z790 dark hero USB speeds all over the place. Enabling XMP makes it USB 2

[greggyp89]

My USB speeds where getting around 40 Mbps in my build for 8k video editing. So I spent the whole weekend trying to check drivers and settings. I tried everything and then decided to clear cmos. After that I'm getting very limited USB 3 speeds. It's up for one second and then down to 40 then down to 30, 20 and even 20 Mbps. M getting super sad my old PC ran my memory card at 400 Mbps no issue. Now I can't use my RAM which I already had to take out two sticks because apparently you can't use all four sticks at ddr5 speeds? I'm new to PC building but everything came out great. I am using PCIe gen 5 NVMe and 3080 graphics card. 

[Jiaszzz_ASUS · Accepted solution]

Hello, @greggyp89 

May I ask if you are currently experiencing issues with USB downspeeding and memory overclocking?
Regarding the USB downspeeding, could you please specify which port on the motherboard you are using, if you have attempted cross-testing with different ports, as well as the current BIOS version?
If you haven't updated to the latest version 0801 released on December 22, 2023, please consider updating and clearing CMOS, then check again.
As for memory overclocking, may I inquire about the brand, model, and part number of the memory you are installing?
We would recommend installing memory listed in the QVL for the ROG MAXIMUS Z790 DARK HERO to ensure compatibility and stability.
Please find relevant information in [Motherboard] How to query (CPU/memory) QVL List? and the "purchasing and installation guide" located in the upper left corner of the QVL page.

Thank you.

[greggyp89]

Yes I have tried all of the USB ports on the case and motherboard. Including the two thunderbolt ports. Oddly enough last night I got so frustrated I cleared CMOS and turned memory overclock off. I had it on XMP tweaked in the BIOS running at 6400 before. The speeds jumped up to 400 megabits per second for about 10 seconds. After that it goes back down. Strangely enough this card reader would go 350 to 400 MB/s the entire drive on my old computer with the same exact cable. I then tried a different card reader that uses SD and got speeds of around 80 to 90 MB per second. Honestly it seems as though it is only the USBC ports affected by the issue. Unfortunately, everything I did with this build did not turn out right. The PCIE Gen 5 drive takes eight lanes of my graphics card. My memory won't run unless I run it at DDR4 speeds. I am using two g skill 48 GB dims at 6400mhz. timings on that memory are CL32 39 39 102  1.35v. I picked these parts out myself and unfortunately I had not heard about these DDR5 issues. Coming from AMD it was nothing but issues for RAM when I first bought it. Afterwards it got sorted out but it took a few years. I was coming to Intel for stability and video editing. I had no idea DDR5 was so, shall I say ridiculous in its infancy. I had four sticks of RAM and I wanted 192 GB. Already my computer is using 85 to 90% of 96gb. So now I'm in a pecurious situation... Been troubleshooting this computer for a week instead of working on my client work. Thank you for the reply

[Jiaszzz_ASUS]

Hello, @greggyp89 

Due to the ongoing local holidays in our area, my response time may experience delays.
I apologize for any inconvenience the delayed replies may have caused.
Regarding the memory installed on the motherboard, please attention to the "Check purchasing and installation guide," which state:

Ensure that all memory modules are from the same validated memory kit. Do not mix DIMMs from different memory kits—even if they are the same brand and model (e.g., two DIMMs each from two different memory kits). 
Mixing and matching DIMMs can result in a failure to boot and compatibility issues.

Additionally, we recommend carefully identifying the software that is consuming a high amount of memory in your system.

Thank you.