[Info-vax] OT: IA-128 ???

[Richard B. Gilbert]

BillPedersen wrote:
> On Oct 18, 7:30 am, "P. Sture" <paul.nos... at sture.ch> wrote:
>> In article
>> <d19d4a6b-e7a0-47bc-b337-be2de56ba... at l9g2000yqi.googlegroups.com>,
>>
>>  BillPedersen <peder... at ccsscorp.com> wrote:
>>> PDP-11/45, the second generation of PDP-11 was also a 16 bit processor
>>> but it had a MMU to access up to 18 bits, so you could have 256KB of
>>> memory, less the 8KB IO space.
>>> PDP-11/70 introduced a MMU which was separated from the Unibus and
>>> provided up to 22 bits memory addressing.  It was STILL at 16 bit
>>> processor.
>> Thanks Bill, I remember mention of 18 bits and 22 bits on an RSX course.
>>
>> We had an 11/34 with (IIRC) 192KB memory and running RT-11. It was with
>> great satisfaction that I took out a load of overlays once we got the
>> memory upgrade.
>>
>> --
>> Paul Sture
> 
> Yes, being able to have a mapped environment rather than an unmapped
> environment made a big difference. And getting to the point where
> there was potentially 64 KB of "free" physical memory for a task/
> program to run in made a big difference to how the program needed to
> be structured as far as overlays.
> 
> Bill.

My boss suffered with the limitations of a PDP-11 only until he scraped 
up enough money to buy a VAX 8200.  That was an enormous relief.  No 
more grubbing around trying to free up five words of memory. . . .