notsofossil wrote:Where do newer motherboard chipsets like the Intel 855 fit into that? Remind me, what is the alternative to ACPI? I keep thinking of ACHI...
Isn't a simple answer... All depends how the system was implemented. For example, there where motherboards with a rather simple, but well made ACPI implementation. These ones will work well with Win98/WinME and Win2k even with ACPI enabled. There are modern 855/865 based machines with _OS initialization procedure for legacy OSPM drivers... Win98 and ME will be able to configure these systems even with ACPI enabled and having a post-2001 ACPI table set... Other problem is that many post-2001 ready for XP systems have no way to disable ACPI or the APICs (Win98/ME doesn't like APICs at all).
A starting point would be to say that every PIII and older system will be able to handle Win98SE and ME in a stable way with ACPI disabled and a minimal loss in functionality... Thats because BIOS firmware in these systems has all the fallback legacy functionality, like APM, PCIBIOS enumerators and ISAPnP components, to configure the system without the help of ACPI tables. Also many PIII boards don't include IRQ integrated hardware eaters, like USB2, so you can manage to get the system full working with only 15 IRQs.
After PIII your mileage will vary, and the only way is to test the configuration thoughfully, with 865 based boards being the top... After that, even if you manage to install WinME in a PCIe chipset, the functionality and stability loss can be enough bad to make it worth, even if you manage to disable ACPI, disable APIC and make your system to enable the old style IRQ logic.