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Path: utzoo!utgpu!water!watnot!watmath!clyde!masscomp!hank
From: hank@masscomp.UUCP
Newsgroups: comp.arch
Subject: Re: 64 Vs 32
Message-ID: <1500@masscomp.UUCP>
Date: Mon, 23-Mar-87 14:34:41 EST
Article-I.D.: masscomp.1500
Posted: Mon Mar 23 14:34:41 1987
Date-Received: Wed, 25-Mar-87 01:15:49 EST
References: <3810013@nucsrl.UUCP> <28200016@ccvaxa> <1308@steinmetz.steinmetz.UUCP> <3436@iuvax.UUCP> <5954@amdahl.UUCP>
Sender: news@masscomp.UUCP
Reply-To: hank@masscomp.UUCP (Hank Cohen)
Distribution: world
Organization: MASSCOMP -- Bethesda Md.
Lines: 35
Keywords: 370 64 bits
Summary: sys 370 does not have 64 bit operations


In message <5954@amdahl.UUCP> chuck@amdahl.UUCP (Charles Simmons) writes:
> 
> By the by...  Amdahl mainframes (and hence probably IBM mainframes
> as well) do support 64 bit integers.  
>
Well I haven't got a POO here just my trusty yellow card, the System
370 Reference Summary, but I don't remember any 64 bit integer
operations on system 370.  There are decimal operations that can go up
to 16 digits or 8 bytes, mabe more I never actually used them, but
integer operations are limited to 32 bits.
     What Chuck may be thinking about are the 64 bit long integers
supported by UTS C.  These things used to be called longs but when UTS
went public people were porting vax and pdp-11 UNIX applications to
UTS and the tendency of DEC programmers to treat longs and ints
interchangably led to problems when longs were 64 bits.  Personally I
liked having chars shorts ints and longs all different lengths but the
market prevailed and longs became long longs (Yecch!!).  I don't know
if this is still the case.  Whatever they are called the 64 bit longs
in UTS C are all implemented as compound operations utilizing multiple
machine registers and multiple instructions.
     The motivation for 64 bit longs in UTS C is simple, there are several
objects in the 370 world that are 64 bits long.  First and foremost is
the PSW, the Program Status Word for you non IBM types.  The PSW
contains the program counter and condition code bits among other
things.  The Channel Command Word or CCW and Channel Status Word or
CSW are also 64 bit objects that the operating system must be able to
manipulate easily.  Bit field operations on 64 bit quantities are
particularly important in developing an operating system for system
370.  One should be able to define fields that span the 32 bit boundry
without worrying about alignment.  

	Hank Cohen	masscomp!hank
	MASSCOMP	7315 Wisconsin Ave. Suite 1245W 
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