5,1 - Bootcamp on AHCI M.2 Drive - Extremely slow Windows 8.1 boot time?

[MacOS 8.6]

I have an M.2 AHCI hard drive installed in my 2010 Mac Pro, with Windows 8.1 installed on it. (The entire drive is dedicated to Windows, as opposed to a Windows partition and macOS partition.

The Windows drive is a PLEXTOR PX-G128M6e (AHCI M.2) installed into a Lycom DT-120 M.2 PCIe to PCIe 3.0 x4 Adapter.

The Windows drive takes forever to start up. (Like literally two-five full minutes). This drive is extremely fast, once it has booted into Windows. I have run the BlackMagick benchmark within Windows to ensure the drive's speed.

Have I installed Window 8.1 the "wrong" way on this drive?

 

[crjackson2134]

It’s a known issue with some m.2 devices... I’m guessing you have the Windows SSD in Slot 3 or 4.

 

[MacOS 8.6]

The Windows drive is actually in Slot #2. (Please see attached image.)

 

[crjackson2134]

The Windows drive is actually in Slot #2. (Please see attached image.)

View attachment 776729

Have you tried Slot #3? You won’t be booting Win/macOS at the same time, so there isn’t a penalty for running in shared lanes.

I’m not really familiar with this device, perhaps it’s not the best choice for a cMP.