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From: jseigh <jseigh_es00@xemaps.com>
Newsgroups: comp.arch
Subject: Re: is Vax addressing sane today
Date: Wed, 11 Sep 2024 07:48:36 -0400
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On 9/11/2024 2:24 AM, Anton Ertl wrote:
> Thomas Koenig <tkoenig@netcologne.de> writes:
>> John Levine <johnl@taugh.com> schrieb:
>>> S/360 had signed and unsigned adds in the 1960s, with optional
>>> trapping for signed overflow. OS/360 let you catch the traps and z
>>> still does but it is not my impression that many programs did or do.
>>
>> With trapping, I understand.  Without trapping - what is the
>> difference on a two's complement machine?
> 
> Possibly in the flags set.  The S/360 has a pretty perverse flags
> architecture.

In the EC PSW from my yellow card
   bit 20 fixed-point overflow mask
   bit 21 decimal overflow mask
   bit 22 exponent overflow mask
   bit 23 significance mask

BC mode was bits 36 thru 39.

Joe Seigh