What's the differences between Windows XP's HALs?

[vipejc]

ACPI Multiprocessor PC

ACPI Uniprocessor PC

Advanced Configuration and Power Interface (ACPI) PC

Compaq SystemPro Multiprocessor or 100% Compatible PC

MPS Uniprocessor PC

MPS Multiprocessor PC

Standard PC

Standard PC with C-Step i486

Other

[Tripredacus]

ACPI being motherboards that support APM (Advanced Power Management) type options like sleep and hibernate. The UP and MP are for UniProcessor (single CPU or core) and MultiProcessor (2 or more CPUs or cores). An MP HAL will also be applied to a single CPU with Hyper-Threading, such as P4 and newer Celerons.

http://support.microsoft.com/kb/309283

Any more information about the HAL is bound to be quite technical. I can't find any technical items in the first 3 pages of The Google results. Maybe I'm not searching for the right things...

[cluberti]

The MPS HAL options are the same as the Standard PC HAL options, but with support for multiple processors and Advanced Power Management (APM). MPS HALs do not support ACPI, though, whereas the ACPI HALs obviously do (ACPI HALs support machines that use both ACPI and APM - if you have a system that supports APM only, you will use an MPS HAL).

The Compaq SystemPro HAL is specific to old Compaq SystemPro machines and non-PCI Compaq ProLiant machines. The SystemPro was basically a server board design in a desktop chassis and was of course a custom motherboard design (and as such needed a special HAL to work properly - it was from 1989 after all). Non-PCI-based ProLiant machines used a similar setup, and thus worked properly with the SystemPro HAL. Again, these things are ancient, so running XP on them for anything other than some sort of nostalgia or a joke would be unwise . These would be better running NT 3.5x or 4.0 if they had to run Windows.

The ACPI HAL supports APM power, but also supports the newer ACPI system and power design, as well as APIC in addition to the original x86 PIC processor designs from the original x86 8086 and the PC/XT. If you have a system that meets these requirements, you will use the ACPI Multiprocessor or Uniprocessor HAL on an APIC machine, and the regular ACPI PC HAL on a non-APIC machine that still supports ACPI.

The "other" HAL type I've never seen used, but it would come up if a system didn't even meet the "Standard PC" HAL requirements (an Intel 486 CPU or compatible, or higher, and doesn't fall into one of the other HAL types). I suppose really old Cyrix or AMD CPUs "could" have fallen into this bucket, but most of those were Intel compatible at this time.

There's more than that, but Technet has some additional information if you want to get geeky about what hardware types cause which HAL to be used.