14 Jan
2013
14 Jan
'13
6:02 p.m.
On 14/01/2013 16:42, Dave McGuire wrote:
Except for 11/84 and 11/94 ;-)
11/53 and 11/93 (and /94) have memory on the CPU but can also access
QBus and PMI memory. QBus devices can access that as if it were on a
separate card.
>> Is that true of Qbus, though? I thought a
memory cycle monopolises
>> the bus.
>
> I _think_ you're right, but, as I wrote,
Mouse is right.
Do all PDP-11s
use Qbus memory? None of them have memory directly on
the CPU card (or, if they do, still generate Qbus cycles)?
Unibus PDP-11s don't use Qbus memory. ;) And several PDP-11 CPU cards
have onboard memory. The ones that use PMI don't (AFAIK) generate Qbus
cycles for memory access.
Yes, they do. PMI just adds some extra control signals which are passed
over the CD interconnect. Several normal QBus control signals are also
used, as of course are the BDAL lines.
--
Pete Peter Turnbull
Network Manager
University of York