21 Nov
2007
21 Nov
'07
6:37 p.m.
ons 2007-11-21 klockan 12:00 -0600 skrev "John A. Dundas III"
<dundas at caltech.edu>:
Jerome,
I can speak for RSTS with some authority, RSX with somewhat less authority.
At 9:17 PM -0500 11/20/07, Jerome H. Fine wrote:
I thought RSTS/E had some way of remapping the address space as well.
Can't you remap parts of your memory to some shared region, for example?
I doubt that RSX-11 or RSTS/E allow a user access
to the IOPAGE
even via PREVIOUS DATA space. Can anyone confirm this assumption?
Address space in the I/O page for RSTS jobs (processes) was not
directly available. The APRs are always controlled by the OS. It
MIGHT be possible for a privileged job to use PEEK/POKE SYS calls to
access the I/O page in the way you suggest but it would be
particularly difficult. RSX had a bit more flexibility (opportunity) in this
regard. I
believe you can set up a CRAW$ (create address window) directive in
either Macro or Fortran to achieve the desired result.
Yes with reservation. CRAW$ (create address window) is as a part of
doing dynamic remapping of your address space.
However, CRAW$ always required a named memory partition. You cannot
create an address window to an arbitrary memory address.
Also, the memory partitions have protections and ownership associated
with them.
On most systems, CRAW$ cannot get you access to the I/O page, simply
because normally you don't have an address space and a partition
associated with the I/O page.
But if such a partition is created, then CRAW$, in combination with MAP$
would allow you to access the I/O page.
The same thing can also be achieved even without CRAW$/MAP$, since you
can specify mapping that your task should have already at task build
time, with the COMMON and RESCOM options to TKB.
Johnny