14 Jan
2013
14 Jan
'13
4:42 p.m.
On 01/14/2013 11:31 AM, Mouse wrote:
I _think_ you're right, but, as I wrote,
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.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
In general, it's possible, depending on the memory
subsystem, that
DMA out of memory does not interfere with CPU access to memory
unless they are accessing locations too close to one another (eg,
the same 32-bit line [...]
Is that true of Qbus, though? I thought a memory cycle
monopolises
the bus. > I don't know enough of PDP-11 memory
subsystems to know whether
> either of those is true of any of them, though.
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)?