15 May
2014
15 May
'14
8:41 p.m.
On Thu, May 15, 2014 at 7:01 PM, Paul Koning <paulkoning at comcast.net> wrote:
On May 15, 2014, at 5:52 PM, Eric Smith <spacewar at gmail.com> wrote:
should
There's also no such thing as a Unibus LSI-11. (Though there are ways to
connect an LSI-11 to a Unibus.)
On Thu, May 15, 2014 at 3:12 PM, Mark J. Blair
<nf6x at nf6x.net> wrote:
>
> On May 15, 2014, at 10:26 , Christian Gauger-Cosgrove <
> captainkirk359 at gmail.com> wrote:
>> 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.
>>>
>>
>> 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 still work fine.
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.