performance: 0.982
x86: 0.975
architecture: 0.972
graphic: 0.802
mistranslation: 0.802
device: 0.801
arm: 0.636
semantic: 0.617
permissions: 0.351
files: 0.332
debug: 0.323
register: 0.309
boot: 0.307
network: 0.289
risc-v: 0.279
PID: 0.278
socket: 0.272
hypervisor: 0.252
user-level: 0.242
vnc: 0.236
i386: 0.225
VMM: 0.170
ppc: 0.154
kernel: 0.140
TCG: 0.124
virtual: 0.089
peripherals: 0.086
KVM: 0.065
assembly: 0.048

x86 (32-bit) multicore very slow, but x86-64 is fast (on macOS arm64 host)
Description of problem:
More cores doesn't slow down a x86-32 guest on an x86-64 host, nor does it slow down an x86-64 guest on an arm64 host. However, adding extra cores massively slows down an x86-32 guest on an arm64 host.
Steps to reproduce:
1. Run 32-bit guest or 32-bit installer
2.
3.

I have replicated this over several OSes using homebrew qemu, source-built qemu and UTM. This is not to be confused with a different bug in UTM that caused its version of QEMU to be slow.

This also seems to apply to 32-bit processes in an x86-64 guest.
Additional information:
https://github.com/utmapp/UTM/issues/5468