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From: firth@sei.cmu.edu (Robert Firth)
Newsgroups: comp.arch
Subject: Re: 48-bit computers
Message-ID: <22383@as0c.sei.cmu.edu>
Date: 11 Mar 91 13:20:37 GMT
References: <666@spim.mips.COM> <1991Mar9.115028.23096@hq.demos.su> <7572@mentor.cc.purdue.edu> <13272@darkstar.ucsc.edu>
Reply-To: firth@sei.cmu.edu (Robert Firth)
Organization: Software Engineering Institute, Pittsburgh, PA
Lines: 24

In article <13272@darkstar.ucsc.edu> haynes@felix.ucsc.edu (99700000) writes:

>Also 48 is a nice number for packing all kinds of bytes and nibbles into,
>since it has so many divisors.  I spoze that's less important now that
>the price of memory has gone down so much compared to 1964.

Indeed it was.  Here is one list, from the KDF9 programming manual, p 24:

THE KDF9 WORD HAS 48 BITS ...

IT MAY BE USED AS...

	Eight 6-Bit Alpha-Numeric Characters
	One 48-Bit Fixed-Point Number
	Two 24-Bit (Half length) Fixed-Point Numbers
	Half of a 96-Bit (Double Length) Fixed-Point Number
	One 48-Bit Floating-Point Number
	Two 24-Bit (Half length) Floating-Point Numbers
	Half of a 96-Bit (Double length) Floating-Point Number
	Three 16-Bit (Fixed point) Integers
	Six 8-Bit Instruction Syllables

An instruction was 1, 2 or 3 syllables; an address was 15 bits.
O, memory!  We shall not see its like again.