Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!UUNET.UU.NET!mcsun!ukc!cam-cl!cet1
From: mcsun!ukc!cam-cl!cet1@UUNET.UU.NET ("C.E. Thompson")
Newsgroups: comp.lang.asm370
Subject: Storing into the CAW (was: (none))
Message-ID: <8910210815.AA12453@brazos.rice.edu>
Date: 20 Oct 89 14:56:23 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: IBM 370 Assembly Programming Discussion List <ASM370%UCF1VM.BITNET@ricevm1.rice.edu>
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In article <8910181519.AA05760@brazos.rice.edu>
PERSHNG@YKTVMH.BITNET ("John A. Pershing Jr.") writes
>CMS normally runs all programs in (virtual) Supervisor State -- if you
>find that you are in problem state, then there is something amiss.
>
>However, to try to keep you from shooting yourself in the foot, CMS
>protects its own storage areas with a Storage Key of x'F', and sets all
>"user" pages to a Key of x'E'.  This is probably why you are having
>difficulty storing into the CAW.  There are a number of ways to get
>around this annoying behavior ...

All of which he gives correctly. However, there is another point to
keep in mind: doing your own I/O instructions, and relying on things
like the CAW, is going to stop working when (if) you have an XA mode
virtual machine. It is better, where possible, to use the synchronous
I/O diagnose instructions.

Chris Thompson
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