I just finished installing the 1903 update on 3 machines; 2 PCs and my 5,1 Mac Pro. The 2 PCs installed without problems. The Mac Pro on the other hand, BSOD's within seconds of getting to the desktop with "WDF_violation". I rolled it back to 1809 and its working again. I am thinking this is because I have AHCI enabled, instead of the forced IDE mode. Has anyone else encountered this? I will probably have to go back to IDE mode, upgrade and then go back to AHCI if I want to.