Canon Cat -- what's it really like?

Eric Smith eric at
Mon Mar 7 04:43:38 CST 2005

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.


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