I recently installed Windows 98 on a bare-metal Ryzen 9 9900X system. The install initially failed with an NTKERN error, which many posts blamed on the CPU. It turns out it was actually a SATA/AHCI issue - check out this video if you're curious.

Ironically, the CPU was running incredibly slow.

During installation and regular use, this wasn't obvious. But after installing 3DMark 2001, I noticed that texture decompression took way longer for such a fast CPU. Running SiSoft Sandra 99, my 4.4GHz CPU scored only about 1.1K points - comparable to a Pentium II 450, far below the 20K+ it should get.

After some digging, I found the culprit: any PCI-E card installed in the x1 slot on my Asus Prime X670-P motherboard causes this slowdown. I first suspected a USB polling issue with a PCI-E to USB card (VIA6212 chip), but the problem occurs with any card.

I’m now curious what might be causing this, especially since CPU load never hits 100%.