12 Oct
2007
12 Oct
'07
1:10 p.m.
On Fri, 12 Oct 2007, Torsten Duwe wrote:
The MC146818 is ISA legacy, so dev/isa has my vote. Pulling out any PC-specific or firmware-dependent semantics would be perfect, though.
Well, to be exact, MC146818 and anything in the 0x00-0xff port I/O space is motherboard, not ISA. ISA port I/O space is 0x0100-0xffff in theory (address lines up to the bit #15 are driven on I/O cycles) and 0x100-0x3ff in reality (many cards did not decode address lines from the bit #10 upward).
And, unlike ISA (in most cases), it is still there in x86-based PC/AT-class systems, usually in the south bridge. OTOH, the 0x100-0x3ff stuff migrated to the so called LPC bus and typically got reduced to some super-I/O chip hanging off there.
Maciej