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From: mark@applix.UUCP (Mark Fox)
Newsgroups: comp.arch
Subject: Re: *Why* do modern machines mostly have 8-bit bytes?
Message-ID: <571@applix.UUCP>
Date: Thu, 6-Aug-87 14:52:24 EDT
Article-I.D.: applix.571
Posted: Thu Aug  6 14:52:24 1987
Date-Received: Sat, 8-Aug-87 14:54:59 EDT
References: <142700010@tiger.UUCP> <2792@phri.UUCP> <8315@utzoo.UUCP> <3532@ihlpg.ATT.COM> <1037@vaxb.calgary.UUCP> <17721@amdcad.AMD.COM>
Reply-To: mark@applix.UUCP (Mark Fox)
Organization: APPLiX Inc., Westboro MA
Lines: 25

In article <699@elmgate.UUCP> ram@elmgate.UUCP (Randy Martens) writes:
>By the way, if I am not mistaken, the Data General Nova 2200 of yesteryear 
> used a 10 bit byte.  And a nine bit tape.  This was weird

You ARE mistaken.

The first Nova's could only transfer 16 bit words between accumulators or
I/O devices and memory so byte manipulation was done entirely in software.
However, the later Nova's and microNova's had byte instructions that were
modeled after widely-used load- and store-byte subroutines.

These subroutines/intructions worked as follows: When a byte is moved from
memory to an accumulator, the high-order half (16 / 2 = 8 bits!!) of the
destination ac is cleared. When a byte is moved from an accumulator to
memory, the other byte in the memory word is unchanged.

DG sold both 9 and 7 track tape systems. The ninth track was used for parity. I
forget how the 7 track tapes were formatted.

By the way, there were Nova 1200's, 1220's, and 2's. I have never heard of a
2200.
-- 
                                    Mark Fox
       Applix Inc., 112 Turnpike Road, Westboro, MA 01581, (617) 870-0300
                    uucp:  seismo!harvard!m2c!applix!mark