Am 28. März 2024 14:09:52 UTC schrieb Mark Cave-Ayland <mark.cave-ayland@xxxxxxxxxxxx>: >On 27/03/2024 07:09, Gerd Hoffmann wrote: > >> On Tue, Mar 26, 2024 at 01:30:48PM +0000, Mark Cave-Ayland wrote: >>> Heh I've actually been using isapc over the past couple of weeks to fire up >>> some old programs in a Windows 3 VM :) >> >> I'm wondering why these use cases can't simply use the 'pc' machine >> type? >> >> The early pci chipsets of the 90-ies have been designed in a >> backward-compatible manner, with devices such as the IDE controller >> being mapped to the standard ISA ioports. So even an historic OS which >> does not know what PCI is can run on that hardware, by simply talking to >> devices using the standard ISA io ports ... > >Hmmm that's a fair point: I think the pc machine has a PCI-ISA bridge included, so ISA devices can be plugged in as needed. The reason I ended up on that configuration was because I ended up chasing down a regression, and wanted to quickly eliminate things such as ACPI. In theory you could pass `-M acpi=off` to not instantiate the PIIX4 ACPI function, essentially turning the Frankenstein-PIIX4 SB into a PIIX3. However, this also removes SMI registers used by SeaBIOS to handle SMM setup which may create unwanted side effects. On a real PIIX3, these registers are located in the ISA function. I wonder if it made sense to implement that for greater compatibility. What do you think? Gerd, what do you think w.r.t. SeaBIOS? Best regards, Bernhard > > >ATB, > >Mark. > > _______________________________________________ Devel mailing list -- devel@xxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxx
