Though Intel Macs are a dying breed, many of them still have some juice left with eGPU and dGPU support, so long as their CPUs are up to the tasks. It means Intel Macs still serve as good Windows PCs, possibly for x86 tasks in Windows environment. I won’t go in to details in this post, but my experience with Apple Silicon was shockingly inconsistent with all the synthetic benchmark scores I could pull up. Some of the tasks I was using 2019 Mac Pro (equipped with workstation Xeon processors) were not only faster Apple Silicon MacBook Air, even after heat throttled, it managed to either finish earlier or within similar timeframe.

Instructions

I’m running on the assumptions you are doing this on an existing or well-used Intel Mac, not a new installation.

1. In Disk Utility, create a third partition (after macOS and Windows) by removing the free space from Mac.* This space will later be merged with Windows partition, so now would be the good time to plan ahead as well.
2. Restart to Boot Camp Windows.
3. You need a tool that can merge partitions, such as MiniTool Partition Wizard Free. From the tool, delete the third partition then merge the empty space with Windows partition. Be cautious not to confuse which partition is which.
4. It is likely the tool will ask you to restart, as the task involves merging with the active partition. After the restart, the tool will start the task on launch. Once finished, the tool can be removed.
   

*If Disk Utility is unable to create a third partition due to “snapshot tidemarks” (used space detected on Disk Utility is greater than the actively used space), you need to remove the snapshots to free the spaces. Snapshots can be deleted from Disk Utility as well. View from Menu Bar > choose Show APFS Snapshots. It will display list of snapshots under Mac partition. Deleting the snapshots will have no impacts on current files.

Afterthoughts

If “snapshot tidemarks” warning had you tied back, it’s nothing to be worried about. The way APFS handles files on SSD is that it doesn’t technically “modify” files; instead, it keeps adding onto what the changes are. The results we see and the spaces used that the system report is different from what Disk Utility sees because the ledger (the history of those changes) may be bigger. It may sound counter-intuitive, but it is optimized for SSDs.

I know Boot Camp support is likely to be abandoned. I will discuss it further in another post, but Apple Silicon does seem to outperform traditional x86 despite what synthetic benchmark implies. I believe part of the reasons stems from many softwares have already transitioned to native Apple Silicon support, and x86 support, especially on an aging hardware, is dying out. Of course, the case can also be made in vice-versa, where x86 softwares running poorly on Apple Silicon Mac, mostly video games that are supposed to be native but somehow run worse on near-equivalent hardwares.