PDP-11 memory question

From: Tom Leffingwell <tom_at_sba.miami.edu>
Date: Mon Jan 7 17:30:09 2002

I'm sure whether it does or not, although I do sort of remember the
limited documentation implying it, but looking back through it can't find
it.

On Mon, 7 Jan 2002, Jerome Fine wrote:

> Do you know if the application programs are using extended memory?
> If so, they gain much more than they loose, especially if they IOPAGE is
> not required - and even more so if they can use more than one window.
> As I stated in another post, RT11XM allows the user to request all the addresses
> from 20000 to 177776 (56 KBytes) to be set up in extended memory
> while still keeping PAR0 in the normal physical space from 00000 to 17776.
> This restriction is essential when an ISR (Interrupt Service Routine) is
> required. Otherwise, if the program uses memory in the normal manner
> (MACRO.SAV is a good example), the use of VBGEXE automatically
> sets the program up COMPLETELY in extended memory and makes
> all 64 KBytes available for code and especially data or tables. And
> providing sufficient additional extended memory is available, more extended
> memory can still be used as well - although the two are rarely combined since
> once a program starts to use extended memory, it usually does everything
> for itself.
>
> Note that VBGEXE probably can't be used in RT11XM when the program
> uses VIRTUAL arrays since I seem to remember that one of the upper PARs
> is required. So there are some limitations.
>
> Sincerely yours,
>
> Jerome Fine
>
Received on Mon Jan 07 2002 - 17:30:09 GMT