[Info-vax] OpenVMS.Org quick pool

[Stephen Hoffman]

On 2012-08-24 14:43:55 +0000, Johnny Billquist said:

> On 2012-08-24 14:48, Stephen Hoffman wrote:
>> On 2012-08-24 02:58:03 +0000, Johnny Billquist said:
>> 
>>> Oh. I should probably point out that "22-bit address" is the physical
>>> addressing of the machine. Virtual addresses are always 16 bits, even
>>> on modern machines with 22-bit physical addresses.
>> 
>> So you don't know how to or haven't had to program a PDP-11 box past
>> 16-bit addressing, or another analogous use of (lowercase-W) windows? Ok.
> 
> Huh? Are you saying that I'm wrong... I am not.

What you're reading in the PDP-11 manuals is correct, as far as it 
goes.  A PDP-11 does have 16-bit addressing.

It is feasible to exceed that limit; to address more memory than what 
that 16-bit addressing would allow, from within an application.

> And yes, I've done plenty of coding under RSX, using large memory 
> regions. Your virtual address is still only 16 bits. What that 16-bit 
> virtual address resolves to in the 22-bit physical address space is a 
> different story, and don't change that my code only deals with a 16-bit 
> virtual address.
> I can probably recall and present exactly how the PDP-11 works straight 
> from my head without checking the documentation.
> 
> Maybe you need a refresher on what a virtual address is? :-)

I'll leave it to you to decide which one of us is more familiar with 
virtual addressing, and how to use virtual addressing (limits and all) 
to advantage.





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