30 Oct
2010
30 Oct
'10
7:49 a.m.
On 10/30/10 2:39 AM, Chuck Guzis wrote:
My take on the PDP-11 trailblazing was UNIBUS, which
essentially let
I/O and memory cards be plugged into the same bus without (much)
regard to placement. Memory-mapped I/O appears to be an outgrowth of
that philosophy. I don't think anyone even mentioned UNIBUS in the
PDP-11 discussion...
This happened right around the same time as the introduction of the
PDP-8/e with its Omnibus, which is very similar in that regard, though
the I/O system is...how shall I put it; OH SO VERY different. (for
non-PDP8 people: plugging I/O controllers into the bus slots adds
device-specific instructions, called "IOTs", to the machine's
instruction set)
-Dave
--
Dave McGuire
Port Charlotte, FL