7 Mar
2005
7 Mar
'05
2:43 a.m.
Ethan wrote:
My recollection is that the Apple II motherboard
pre-decodes address
ranges on behalf of the cards and does _not_ present A0-A15 raw to the
slot.
A0-A15 are on pins 2-17 of the slot connector. They are buffered, both
to increase the drive capability and because the standard 6502 didn't
provide a way to disable the on-chip address drivers, which is necessary
to support DMA.
Most cards don't need to use A12 through A15 because of the available
decode lines, but they're certainly available.
Eric