15 May
2014
15 May
'14
6:01 p.m.
On May 15, 2014, at 5:52 PM, Eric Smith <spacewar at gmail.com> wrote:
On Thu, May 15, 2014 at 3:12 PM, Mark J. Blair
<nf6x at nf6x.net> wrote:
Be careful there. The PDP-11/20 doesn?t have MMU either. And the software indeed
manipulates 16 bit addresses. But the I/O bus (Unibus) has 18 bit addresses. The bus
interface supplies 0 for the upper 2 bits if the lower 16 are less than 0160000, and two
bits of 1 if the lower 16 are 0160000 or higher (i.e., the PDP11 I/O page space).
So on Unibus at least, there is no such thing as a 16 bit peripheral; all are 18 bit by
definition.
paul
On May 15, 2014, at 10:26 , Christian Gauger-Cosgrove <
captainkirk359 at gmail.com> wrote:
The LSI-11 and LSI-11/2 (PDP-11/03, in other words) processors are
only 16-bit addressing, actually. If my recollection is correct.
I believe that my system's backplane is the 18-bit variety, as opposed to
the 22-bit variety. I think that the UC07 card will support both 18 and 22
bit busses. If I understand correctly, the processor directly addresses 16
bits but uses some sort of bank mapping register(s) to address additional
bits, but I'm not positive about that.
The 11/03 doesn't have memory management, so it's limited to strictly
16-bit addressing. However, peripherals that use 18-bit addressing should
still work fine. On 15 May 2014 13:08, Cory Smelosky <b4 at
gewt.net> wrote:
> The /03 is 18-bit right? The SCSI adapter I have has an option for
18-bit
addressing.