On Mon, 19 Jan 2015, Paolo Bonzini wrote: > >> The reason I asked is simply because ISA devices never do MMIO (apart > >> for the VGA window). > > > > You mean in the QEMU world? At least physical SCSI and Ethernet > > adapters had a MMIO space for the onboard ROM. > > Uh right, ROMs count as MMIO too.
Some ISA Ethernet cards also used MMIO for r/w access, probably to get at packet memory more efficiently (I don't remember the details offhand) as port I/O transactions were notoriously slow; in any case this is where the "Memory" field printed by `ifconfig' under Linux comes from. I'm sure there was other ISA equipment too using MMIO for one purpose or another. On a PC/AT class x86 computer these resources would normally be allocated somehow to the memory space in the 0xd0000-0xeffff range, to work with real-mode software. With "somehow" usually meaning jumpers, though newer cards may have had DOS configuration software available to set it up, in a similar manner to how ECU configured port I/O and MMIO resources for EISA equipment. BTW there were ISA DRAM expansion cards in existence too. Maciej
