RE: Re: MVS under VM\ESA

> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On Behalf Of kerravon86
> Sent: 13 August 2010 23:52
> To: [email protected]
> Subject: [H390-VM] Re: MVS under VM\ESA
> 
> 
> --- In [email protected], Jay Maynard <jmaynard@...> wrote:
> >
> > On Fri, Aug 13, 2010 at 02:37:20PM -0400, Dave McGuire wrote:
> > > 
> > >   Does such a modified 3.8j exist?  I'm very much interested in 
> > > doing this.  I guess I was just assuming all along that it'd work 
> > > out-of-the-box.
> > 
> > This is the same problem as running 3.8J on a P/390. I do that by 
> > IPLing in single step mode, manually altering CR7 
> appropriately, the 
> > setting it to run and going on. It should be easy to patch 
> IEANIP00 to 
> > do this. MVS never touches CR7 after IPL.
> 
> I assume by CR7 you mean CR0.7, as CR7 is to do
> with a secondary address space.
> 
> CR0.7 is described here:
> 
> http://publib.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/DZ9AR006/3
> .4.1.1?SHELF=&DT=19990630131355&CASE=
> 
> but doesn't seem to match the description given
> by Ivan either.
> 
> How many instructions do you need to single-step
> through before altering the appropriate register?
> 
> What is the instruction that you look for before
> stepping over it?
> 
> I'm not sure what to look for in the source code.
> 
> Note that the ieavnipm and ieavnpm3 source files
> have been brought up-to-date so far.
> 
> http://mvs380.cvs.sourceforge.net/viewvc/mvs380/mvssrc/asm/iea
>vnipm.asm?view=markup
>
>Also, I assume that if this is an otherwise unused
>bit, MVS 3.8j will continue to run on standard
>Hercules S/370?

Yes

>Also, why is this necessary at all, from VM or
>P390's perspective?

Because "old" hardware allows a separate storage key for each 2k, later
hardware (including P/390) every 4k.

>And also, how does VM/ESA or P/390 manage to cope
>with MVS 3.8j doing old-style I/O, or 370 DAT?

It doesn't really. Its mostly handled by the SIE facility....

>Do they support S/370 mode?  If so, why the
>requirement for a change in CR0 or whatever?

Yes they (well the underlying hardware) support S/370 mode. The change for
CR0 is needed on any hardware that only supports 4k storage keys. This was
also an issue running VM/SP on some XA capable boxes. IBM's solution was to
sell you VM/HPO..

>
>Thanks.  Paul.



Dave Wade G4UGM
Illegitimi Non Carborundum