But... if you start applications inside your VM it will want the full 8 Gb you've allocated not the 5 Gb it uses at startup?
Good reminder that there's a certain amount of memory tied up with each core (probably mainly page cache and concurrency handling etc).
Edit: I stand corrected!
[1] https://developer.apple.com/documentation/virtualization/vzv...
In my review of macOS virtualisation on Apple silicon, I quoted performance figures that were obtained some time ago, and didn’t consider minimum specifications for a usable VM. Given current interest in running a VM on a MacBook Neo, I thought it would be worth examining these afresh, from macOS Tahoe.
Using the same host, a Mac mini M4 Pro, this time running macOS 26.4.1 on its 14 cores (10 P + 4 E) with 48 GB RAM and a 2 TB internal SSD, Geekbench 6.7.1 scores are slightly faster, on both the host and a guest given 5 virtual cores and 16 GB of virtual RAM:
The last of those gives single precision, half-precision and quantised test results, in that order.
Comparing CPU single-core figures, the VM runs effectively at 98% of the speed of the host. Comparison between the multi-core CPU results is difficult, as the host has more than twice the number of cores, although four of them are E cores. However, given that the host has twice the number of P cores alone, the VM appears to perform rather better than the host on this test.
GPU performance isn’t quite as good, with the VM delivering performance of 95% of that of the host, when the latter isn’t contending for the GPU as well.
The only real disappointment here is the virtual neural engine, which performs far slower than the host on half-precision and quantised tests. We might hope that macOS would process AI tasks using the CPU and GPU rather than the neural engine, when running in a VM.
With the arrival of the MacBook Neo, some wondered whether it would be able to run VMs. While there’s no doubt it should make a good host for Linux, I doubted whether it would be able to do anything useful with macOS in a VM. I was wrong.
To assess how small a macOS VM could be, I ran the same VM of macOS 26.4.1 on progressively smaller CPU core and memory allocations, using my virtualiser Viable. The VM’s display window was set to a standard 1600 x 1000, and I ran Safari through its paces and performed some lightweight everyday tasks, including Storage analysis in Settings.
Starting with 4 virtual cores and 8 GB vRAM, where the VM ran perfectly briskly with around 5 GB of memory used, I stepped down to 3 cores and 6 GB, to discover that memory usage fell to 3.9 GB and everything worked well. With just 2 cores and 4 GB of memory only 3.1 GB of that was used, and the VM continued to handle those lightweight tasks normally.
The only thing to be careful of when creating VMs on Macs with small internal SSDs is their size. Any macOS VM significantly smaller than 50 GB isn’t going to be able to update its macOS, and for comfort and safety you should aim for at least 60 GB. Fortunately, APFS comes to your aid here, as VMs are stored as sparse files, and a basic 100 GB VM should only require about 54 GB on disk. That would be better accommodated on the MacBook Neo with a 512 GB SSD.
Although not the place to try running your LLM, a macOS VM given only 2 virtual cores and 4 GB of memory, as should be feasible in a MacBook Neo, is thoroughly usable and capable of everyday tasks. Bring on the Neos!