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From: davidb@brac.inmos.co.uk (David Boreham)
Newsgroups: comp.arch
Subject: Re: H1 details?
Message-ID: <15856@ganymede.inmos.co.uk>
Date: 4 May 91 17:24:03 GMT
References: <1991Apr25.185728.1306@britesun.radig.de> <1991Apr26.053510.19231@watdragon.waterloo.edu>
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Reply-To: davidb@inmos.co.uk (David Boreham)
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In article <1991Apr26.053510.19231@watdragon.waterloo.edu> ccplumb@rose.waterloo.edu (Colin Plumb) writes:
>vhs@britesun.radig.de (Volker Herminghaus-Shirai) wrote:
>>It also states that they can execute a maximum of eight instructions at once
>
>I haven't even seen it, but I'll bet money that what they mean is one
>instruction and seven prefixes.  On the trasnputer, all the instructions
>have a 4-bit operand field.  Larger operands are built up using prefix
>instructions, which add their 4-bit operand field to the next "real"
>instruction.  Pushing this past one per cycle is pretty crucial to good
>performance.  I doubt they do more than one "real" instruction per cycle.
>-- 
>	-Colin



What ! Come on Colin, where's the smiley ?

Seriously though, when the blurb says ``eight instructions''
it means ``eight operations''. Like an add, a branch, a FP operation,
an address calculation and so on to eight if I could remember
what they all are. 

The prefixing is dealt with by the instruction ``grouper''
and when we say ``eight instructions'' this does NOT include
prefixes. I saw some press comment which mentions a forty-odd
maximum instruction-per-cycle figure---this comes from counting
prefixes and instructions folded into one operation by the
grouper.

The T9000 is a seriously fast machine and you could argue that
the prefixing machanism used in the instruction set helps
by cutting down on memory traffic compared with a RISC machine.

David Boreham, INMOS Limited | mail(uk): davidb@inmos.co.uk or ukc!inmos!davidb
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