How fast is a macOS VM, and how small could it be?
Source: Hacker News
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.
How fast?
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:
- Single‑core CPU – VM: 3,855 Host: 3,948
- Multi‑core CPU – VM: 13,222 Host: 23,342
- GPU (Metal) – VM: 106,896 Host: 111,970
- Neural engine (Core ML) – VM: 5,291 (single‑precision), 8,577 (half‑precision), 6,877 (quantised) Host: 5,973, 41,251, 56,616
The last line gives single‑precision, half‑precision and quantised test results, in that order.
- Comparing CPU single‑core figures, the VM runs at roughly 98 % of the host speed.
- Multi‑core results are harder to compare because the host has more than twice the total cores (including four efficiency cores). Even so, the VM performs competitively relative to the host’s P‑core count.
- GPU performance is close, with the VM delivering about 95 % of the host’s Metal score when the host isn’t contending for the GPU.
- The virtual neural engine lags noticeably on half‑precision and quantised workloads; macOS may fall back to CPU/GPU for AI tasks when running in a VM.
How small?
With the arrival of the MacBook Neo, some wondered whether it could run VMs. While it should make an excellent host for Linux, I doubted its ability to run macOS in a VM. I was wrong.
To assess how small a macOS VM could be, I ran macOS 26.4.1 on progressively smaller CPU‑core and memory allocations using the Viable virtualiser. The VM’s display window was set to a standard 1600 × 1000, and I exercised Safari and other lightweight everyday tasks, including Storage analysis in Settings.
| Virtual resources | Observed memory usage | Behaviour |
|---|---|---|
| 4 cores + 8 GB RAM | ~5 GB | Brisk, fully functional |
| 3 cores + 6 GB RAM | 3.9 GB | Everything worked well |
| 2 cores + 4 GB RAM | 3.1 GB | Lightweight tasks handled normally |
The main caution when creating VMs on Macs with small internal SSDs is the VM’s disk size. Any macOS VM smaller than ~50 GB won’t be able to update its OS. For comfort and safety aim for at least 60 GB. Fortunately, APFS stores VMs as sparse files, so a nominal 100 GB VM typically occupies only about 54 GB on disk—well within the 512 GB SSD of a MacBook Neo.
Thus, even a macOS VM limited to 2 virtual cores and 4 GB of RAM—a configuration feasible on a MacBook Neo—is thoroughly usable for everyday tasks. Bring on the Neos!