> On Jul 13, 2015, at 8:52 PM, Johnny Billquist <[email protected]> wrote:
>
> On 2015-07-13 21:16, Rich Alderson wrote:
>> ...
>
>> [2] With memory management, 18 or 22, in 16-bit segments. Late models could
>> use separate instruction and data segments, for a total of 128KB in use
>> at
>> one time.
>
> ??? What segments??? The PDP-11 have a plain simple page table. No segments
> anywhere in sight. And each page is 8K.
To me, “segment” means a chunk of memory. It doesn’t refer to separate page
tables, or page tables broken into pieces. And as I recall, the terms
“instruction and data segments” were in common use to describe the feature.
The PDP-11 is a bit unusual in that each page is *up to* 8k, the actual size
(and whether it’s the lower or the upper part that is accessible) is specified
by the page description register for that page. Also in that the physical
address of the page isn’t constrained to a multiple of the (max) page size.
paul
