Path: utzoo!attcan!uunet!ncrlnk!ncrcae!hubcap!gatech!ncar!tank!nic.MR.NET!shamash!nis!ems!pwcs!umn-cs!hall!pmk
From: pmk@hall.cray.com (Peter Klausler)
Newsgroups: comp.arch
Subject: Re: Population count instruction (was Re: RISC v. CISC ...)
Summary: correction
Message-ID: <10947@hall.cray.com>
Date: 4 Nov 88 15:08:53 GMT
References: <1622@scolex> <1854@eos.UUCP>
Organization: Cray Research, Inc., Mendota Heights, MN
Lines: 20

In article <1854@eos.UUCP>, jaw@eos.UUCP (James A. Woods) writes:
> Even more eyebrow raising is the related AVL (additional vector logical)
> unit available for certain Cray serial numbers, which amplifies tricks like
> the above by sixty-four.  This second logical vector unit, again
> an NSA-only custom add-on device, might also help such a machine play
> a mean game of chess, but that's a different conspiracy theory ...

I hate to spoil a good conspiracy story, but:

	1) "Second vector logical" is the ability to use the FP multiply
unit as a spare logical unit; it works on all but the earliest X-MPs and Y-MPs,
except maybe the SE machines. The feature is enabled by having the OS set a bit
in your exchange package.

	2) Vector popcount and popcount-parity execute only in the Vector
Pop/Parity unit; they can't use the "second vector logical" feature.
Neither can vector mask instructions, so the feature is really useful
only for basic vector ANDs, ORs, and such.

-Peter Klausler / Cray Research compiler development / Mendota Heights, MN