IRQs (ISA) or INTs (PCI)? 😉

Sorry,
INTs I mean, it's PCI.

ACPI/APIC

I have ACPI BIOS enabled and it's listed in device manager. This board is ACPI 1.1 so it'll work for 98SE.

I have "Programmable Interrupt Controller" installed, I did try to manually install a "Advanced Programmable Interrupt Controller" listed in MACHINE.INF through the add hardware wizard, but I can't select it from the list when I tried that.

Is there a way I can force enable the APIC?

any ideas?

Basically, you need chipset drivers for that board.
I'm afraid there's no hope...

Did you try turning off all onboard USB, Audio, etc ? Running Win98 on a 2020 board based on 2014 tech am surprised Win98 even runs stable...🤣

Win98 isn't compatible with APIC, nor with any technology related to the MPS specification for standard x86 multiprocessor architectures.

When Win98 was in use, APIC was an extra chip which only was installed in SMP boards. Thus basically it meant SMP, which wasn't supported at all by Win98. I don't think there was a real technical limitation supporting APIC through the Windows VMM in Uniprocessor Mode, but since that would have confused their customers to think Win98 would support SMP by extension, they decided to no support it at all, nor the MPS device routing and enumeration mechanisms. Also was a waste of resources giving customers with MPS/APIC boards would anyways use NT, and added complexity to keep it in sync with Windows DOS support...

As workaround you would like to disable almost every built in device (yes, including the USB controllers, which probably are the ones eating your precious legacy IRQs), and then only enable the least necessary ones to use in Win98, including one or two USB controllers for your Mouse, Keyboard and Pendrive if you will use one in Win98. Many modern boards allow you to do BIOS setting profiles, so you don't need modify every setting each time you want to boot with APIC compatible OSs.

And disable USB3 (XHCI controller). It isn't compatible with Win98, and will waste one or two legacy IRQs.

I think the confusing part is this one:

"ACPI aims to replace Advanced Power Management (APM), the MultiProcessor Specification, and the Plug and Play BIOS (PnP) Specification."

https://en.wikipedia.org/wiki/ACPI

MultiProcessor Specification:

"The MultiProcessor Specification (MPS) for the x86 architecture is an open standard describing enhancements to both operating systems and firmware, which will allow them to work with x86-compatible processors in a multi-processor configuration. MPS covers Advanced Programmable Interrupt Controller (APIC) architectures. "

https://en.wikipedia.org/wiki/MultiProcessor_Specification

That's why ACPI and APIC are often being mentioned together, despite them being different.

Also, it didn't really help that Windows 98 had its problems..

"Microsoft's Windows 98 was the first operating system to implement ACPI,[20][21] but its implementation was somewhat buggy or incomplete,[22][23] although some of the problems associated with it were caused by the first-generation ACPI hardware."

https://en.wikipedia.org/wiki/ACPI

From ReactOS archived knowledge, you learn Win98 actually implemented ACPI 1.1 in SCI mode. This is what you would call "ACPI Legacy Mode" or "ACPI in PIC mode". Windows 2000 and XP also implement this mode in the so called "ACPI Standard PC" HAL (HALAACPI). In this mode chipset hardware arbiters are enabled, so in theory, you can share the legacy IRQs between devices if the device allows it (The so called IRQ GSIs/Levels). In practice, many hardware pieces and boards aren't compatible with this, and would choke doing it. Also, SCI mode consumes one legacy IRQ for it (generally IRQ9).

ACPI 1.2 introduces the so called "ACPI Uniprocessor and Multiprocessor modes" which use the APIC. In NT support for these are included in (HALACPI) and (HALMACPI) HALs. These provide real extra IRQs, but also enhances the arbiters and the IRQ sharing levels to fine tune your hardware mapping and management thanks to the APIC. This is completely unsupported by Win98.

I think I might do a reinstall of windows 98 but use that setup /p i switch to disable ACPI this time round.

The reason I'd left ACPI enabled was based off of my experimentation with XP installation where in order to get access to more Interrupt IRQs through the APIC you would need to have ACPI on and use the ACPI HAL.

So I had assumed it would be the same in that in order to have more IRQs available in Windows 98 I would need to have ACPI on.
But it hasn't given me access to any more IRQs and it seems to have been more of a hassle than anything else.

If I can't get more IRQs through an APIC, A second option I could try is turning off PCI IRQ steering, anyone here have any experience with that?

OK, some progress.

I reinstalled Win98SE but this time without ACPI enabled.
Still no extra IRQs, but I've found that my Yamaha YMF744 sound card seems to work correctly in win98 now as it no longer lags horribly whenever it plays a sound. So that's good.

Sound still isn't working for DOS games though.