> The usual layout is that the PCI bus is a direct child of > the root node, and the ISA bus is a child of the PCI bus. > That reflects the "Northbridge + Southbridge" wiring that
That isn't strictly true either. On many PC devices the ISA bus (or LPC bus nowdays) has no heirarchy as such because ISA cycles get issued if the PCI cycles don't generate a response. In addition some cycles go to both busses on some chipsets and there are various bits of magic so the I/O spaces and particularly the memory spaces are intertwined. So it's not a subordinate bus really, its a bit weirder. PCMCIA is probably a sub-bus when you've got a PCI/PCMCIA adapter but ISA in general is a bit fuzzy. And then there are systems like PA-RISC where there are multiple entire PCI/ISA busses hung off the primary bus which is neither 8) There are also various bits of "architectural" space which are on the motherboard (traditionally 0x00-0xFF) but some of which are on the CPU in some cases (Cyrix was 0x21/22 if I remember), and there are other architectural spaces like the ELCR which are "magic". The PC is alas to computer architecture what perl is to programming languages. Alan _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
