On Wednesday, 04/15/2009 at 11:00 EDT, Heiko Carstens
<[email protected]> wrote:

> I agree that it would be better to emit a message to the console. But
> the code that emits the message must be written completely in assembler
> to prevent the compiler from generating instructions that wouldn't work
> on older machines.
> So currently we have this piece of code which is simple and with a
> magic PSW it should be sufficient.
> We might change it, but no promises.

It is standard for any mainframe operating system that cannot IPL to load
a disabled wait state with a PSW that acts as code number in it so that
you can look in a book to find out what it means.  VM, MVS, VSE, and TPF
all do it.  "Come on in!  The water's fine!"  :-)

There is no need for heroic measures to write a nice message to the
console.  Just make sure that the addresses in the PSW are unique for each
condition.  If you can be clever in your use of letters A-F and numbers
(and l33t5peak), you can give informative wait state codes.

Alan Altmark
z/VM Development
IBM Endicott

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