Davids version of ACPI certainly works better than the versions released before he took over development.
There is no doubt about that.
because PRINT01.SYS does not accept interrupts > 15
I think you guys are forgetting, that the DEFAULT operation of PRINT01.SYS, is POLLING mode, which does not use an IRQ. Just leave off the /IRQ parameter. In the early days, that would use a noticeable amount of processor time, but today it is negligible.
There is also the PAR1284.SYS driver. I have no idea if it will help.
Everybody is probably aware of this, but FWIW using PSD=OS2APIC.PSD lets all processors function under these conditions.
Processors work, but there is no power control. That is not too serious on a desktop system, but is not good on a laptop. I have tried that on all of my SMP systems, and it does enable all processors on all of them, but I would only use it, if ACPI did not work. There is no other reason to use it.