Path: utzoo!mnetor!uunet!husc6!psuvax1!burdvax!bpa!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.arch
Subject: Re: More than 32 bits needed where?
Message-ID: <3288@cbmvax.UUCP>
Date: 10 Feb 88 04:48:27 GMT
References: <19667@bu-cs.BU.EDU>
Organization: Commodore Technology, West Chester, PA
Lines: 21

in article <19667@bu-cs.BU.EDU>, bzs@bu-cs.BU.EDU (Barry Shein) says:

>>Another use of more than 32 bits is for normal accounting purposes.

> This was the motivation for packed decimal instruction sets on many
> computers aimed at the business market. They typically used "BCD",
> decimal digits packed one per 4-bit nibble and supported variable
> length operands up to 15 decimal digits.

That old business workhorse, the MOS 6502, also had a BCD math mode.

It does, at least, have an accuracy advantage, in there's no binary rounding
problem with BCD, you get what you pay for in decimal digits.  Of couse, it's
in most cases going to be much slower than normal binary math, and it takes up
more space.

> 	-Barry Shein, Boston University
-- 
Dave Haynie  "The B2000 Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {ihnp4|uunet|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
		"I can't relax, 'cause I'm a Boinger!"