Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!amdahl!nsc!taux01!amos
From: amos@taux01.UUCP (Amos Shapir)
Newsgroups: comp.sys.nsc.32k
Subject: Re: 32000 Un-Nicities
Message-ID: <2945@taux01.UUCP>
Date: 23 Nov 89 13:50:30 GMT
References: <1914@minyos.xx.rmit.oz>
Organization: National Semiconductor (IC) Ltd, Israel, Home of the 32532
Lines: 29
Hdate: 25 Heshvan 5750

In article <1914@minyos.xx.rmit.oz> s872625@minyos.xx.rmit.oz (Chris Cogdon [Brataccas]) writes:
>
>The purpose of this item is to see if anyone knows WHY these un-nicities
>were put there. Or is NSC not as infallible as we think it is.

What makes you think it ever was? :-)

>1) Displacements can only cover 1M of addressing space (512k if you only
>   allow for forward displacements from a fixed base).

That's what's left in the address word after the two size bits are
used up.  When this scheme was designed, nobody was supposed to use
more than 1Gb, and 5-byte addresses were considered even un-nicer.

>2) There is no unsigned multiply and divide.

Yes there are: MEIi and DEIi.

>3) CVTP has no parallel. ie. there is no single instruction which can undo
>   the bit pointer, nor can anything directly use the result.

This is ambiguous, since a bit pointer can be reduced into any number
of possible byte+offset pairs.  If you are satisfied with a minimum-offset
pair, do a LSH, AND, or DEI.

-- 
	Amos Shapir		amos@taux01.nsc.com, amos@nsc.nsc.com
National Semiconductor (Israel) P.O.B. 3007, Herzlia 46104, Israel
Tel. +972 52 522261  TWX: 33691, fax: +972-52-558322 GEO: 34 48 E / 32 10 N