
To run NT 3.1 with MPS HAL on VirtualBox:

First you need to "hack" Virtualbox by changing the IOAPIC_NUM_PINS from 24 to 16 - it means downloading virtualbox source code, changing file src/VBox/Devices/PC/DevIoApic.cpp, then compiling changed sources.

http://www.os2museum.com/wp/nt-3-1-smp/

https://forums.virtualbox.org/viewtopic.php?f=10&t=86531
