Thanks for the link. I have an OK understanding of PCI and PCIe and I'm not sure if I'd find the answer there.
Basically, why do the two virtual PCI - PCI bridges that get created in 'PCI Legacy Mode' have to use subtractive decoding? Why can't they just use positive decoding like normal PCI - PCI bridges.
What specific reasoning of standard PCI that requires subtractive decoding?