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From: LDW@USCMVSA.BITNET (Leonard D Woren)
Newsgroups: comp.lang.asm370
Subject: Re: New System/3x0 Instruction
Message-ID: <9103171023.AA28323@ucbvax.Berkeley.EDU>
Date: 17 Mar 91 09:05:00 GMT
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Reply-To: IBM 370 Assembly Programming Discussion List
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On Sun, 10 Mar 91 13:03:10 -0600,
   Neil Rickert <rickert@CS.NIU.EDU> said:
>  You can't do that in an instruction.  An SVC routine -- yes.  An
> instruction -- no.  The page tables are not a hardware feature but a
> creation of the operating system.  Therefore a hardware instruction
> cannot manipulate them.

Really?  Ever heard of the MVS assists "OBTAIN LOCAL LOCK", "ADD FRR",
etc.?  These are (microcoded) instructions which are sensitive to the
format of MVS control blocks.  Look in the MVS Data Areas manual (or
whatever it's called for your release of MVS.)  In some control blocks
like the ASCB, there are fields marked "this offset fixed by
architecture".  What could that possibly mean except that there are
machine instructions that manipulate those control blocks?


Leonard D. Woren      Senior MVS Systems Programmer
<LDW@USCMVSA.BITNET>  <LDW@MVSA.USC.EDU>      Disclaimer???
University of Southern California             What would be the point?