Windows Latest reports that it affects pre-2012 Macs:
Earlier today, Microsoft announced that it has blocked the Windows 10 version 1903 update on older Mac devices or newer Mac with outdated Apple Boot Camp software. This move affects Windows 10 owners who have installed the operating system on a Mac device introduced before 2012 or those who use outdated Boot Camp software on their new devices.
The hold is due to an unspecified compatibility problem.
Microsoft says affected users may experience an update compatibility hold and receive the message “Mac HAL Driver — machaldriver.sys: Your PC has a driver or service that isn’t ready for this version of Windows 10.”
HAL is a Hardware Abstraction Layer, which is code that sits between hardware drivers — like those for audio — and applications. Effectively, this acts as an interface between Windows apps and the Mac hardware.
The Microsoft support document specifies the relevant versions of the file, and suggests for later Macs that updating Boot Camp may solve the problem:
Specifically, devices with MacHALDriver.sys dated September 24, 2011 01:57:09 or older in Windows\system32\drivers are affected.
Updating your Apple Boot Camp Windows Support Software drivers may allow you to update to Windows 10, version 1903. You may be able to check for updated Windows support software, in macOS, choose Apple menu > App Store, then install all available updates. You can also try the instructions in the Apple support article here.
Microsoft says the company is working on a solution, and hopes to have Windows 10 updates for Mac working for older machines by the end of the month.
We have a whole series of video guides devoted to Boot Camp, including:
- How to install Windows 10 on your Mac using Boot Camp Assistant [Video]
- How to turn the 2016 MacBook Pro into a Windows gaming machine using the compact Akitio Thunder3 + GTX 1050 Ti [Video]
- How to back up and restore a Boot Camp Windows partition on macOS using Winclone [Video]
- How to remove a Windows Boot Camp installation from your Mac [Video]
- How to install Windows 10 on your Mac using a ‘Boot Camp’ external drive via Windows To Go [Video]
- How to install Windows 10 on the 2018 Mac mini using Boot Camp Assistant [Video]
- How to turn the 2018 Mac mini into a capable Windows gaming machine [Video]
- How to: 2018 Mac mini + Nvidia GeForce RTX 2080 eGPU Windows gaming setup [Video]