[parisc-linux] arch/parisc/kernel/realmode_setup.c Question

Ryan Bradetich rbradetich@uswest.net
Tue, 16 Nov 1999 07:02:29 -0700

Frank Rowand wrote:

> Alex deVries wrote:
> >
> > On Mon, 15 Nov 1999, Frank Rowand wrote:
> > > You don't get to choose.  The PDC is either 32 bit or 64 bit.  It's not
> > > a question of what mode the OS is running in, but what the PDC was
> > > compiled for.
> >
> > Hm.  I'm pretty sure that a 32 bit version of HPUX has run on that box as
> > well, so wouldn't that mean that it'd have to be a 32 bit PDC?
> >
> > - Alex
> Nope.  The OS has to figure out what type of PDC it is calling, and properly
> marshall the arguments for the call.
> -Frank

Time for me to show off my ignorance again. :)  As I understand it, the PDC is
firmware, which all the CPU (in a multiple CPU box) share.  I know that when
I installed 11.X on this C200 that I was given the choice to install it in 32
bit or
64 bit mode.  Does this mean the install disk updates the PDC firmware to boot
into either 32-bit or 64-bit mode?

Also looking at the PSW definition for the W bit on page 2-7 and
page 2-8 of PA-RISC 2.0 Architecture by Gerry Kane:

W: Wide 64-bit address formation enabled.  When 1, full 64-bit-offset
is enabled.  When 0, addresses are truncated to 32-bit offsets, for
with existing PA-RISC 1.0 and 1.1 applications.

From PIM dumps, I know all the registers are 64 bit, and the PSW is also 64 bit
this C200..  So it looks like I should be able to switch between 32-bit and
64-bit by
changing the W bit in the PSW?

Ryan Bradetich

P.S.  I will try to query the PDC_MODEL as you suggested as in a previous email

in this thread and post the result when I get home tonight.