Path: utzoo!attcan!uunet!aplcen!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!gvlv2!tredysvr!barry
From: barry@tredysvr.Tredydev.Unisys.COM (Barry Traylor)
Newsgroups: comp.arch
Subject: Re: Computer Architecture methodology
Summary: Over time some ops come, some ops go
Keywords: A Series, B6700
Message-ID: <844@tredysvr.Tredydev.Unisys.COM>
Date: 7 Jul 90 23:04:25 GMT
References: <8533@canterbury.ac.nz> <14279@burdvax.PRC.Unisys.COM> <3329@goanna.cs.rmit.oz.au>
Distribution: comp.arch
Organization: Unisys Corporation,  Tredyffrin, PA
Lines: 34

In article <3329@goanna.cs.rmit.oz.au> ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) writes:
>
>I would love to hear about which of the hardware instructions are now
>regarded as obsolescent and ill conceived.  Are LLLU and SRCH on the way
>out?  What finally happened about the 20-bit physical addresses?  What
>problems does Ada have with the A series?  What's the true story on the
>addition of {HEX|BCD|ASCII|EBCDIC} POINTERs and the later removal of
>BCD POINTER?  Has vectormode been extended?  
>

LLLU (linked list lookup, pronounced lulu), has been deimplemented for all
recent and future machines;  it was an operating systems instruction that
fell out of use.  SRCH (Masked Search) and BMS (bounded masked search, a
new op) are alive, healthy and heavily used in the OS.

The physical addressing limit is 32 bits (4Gwords or 24Gbytes), extendable
in the future to 36 bits, if necessary.  Addressing is done via a global
segment table now.

There currently is no Ada compiler for A Series, although we believe that
Ada would fit well.

BCL (rather than BCD) was largely eliminated 10 years ago.  The expense of
the hardware support for it and the lack of a standard for 6 bit character
sets did it in.  The machine supports a HEX framesize as well as an 8 bit
framesize that can represent either ASCII or EBCDIC.

Vector Mode died shortly after it was discovered that it ran more slowly on
pipelined machines than non-vector mode.  I do not believe that we have
made a machine that supports vector mode for more than 10 years.

Barry Traylor
barry@prc.unisys.com (or whereever this message came from)
Unisys Large A Series Engineering, Tredyffrin Twp, Pa.