Hi, I have similar issue like the guy here: Windows 7 - Skipping ACPI requirement | NTLite Forums
I have 6x Pentium Pro server from 2000’s and unluckily it does not have BIOS ACPI support.
There has been a similar manual approach for Windows XP:
https://www.cpushack.com/2019/01/14/part-2-mini-mainframe-at-home-the-story-of-a-6-cpu-server-from-1997/
Press F5, then choose MPS - Multiprocessor PC. But that does not work.
The last release that supports multiprocessor without ACPI was Whistler Server build 2493.
Basically I think I will need to mod ACPI.sys and perhaps Kernel32? I need Windows Server 2003 or Windows 7 or Windows XP working with SMP processor support and without ACPI.
This 6x Pentium Pro server beats Pentium 4 in multi-threading 