Path: utzoo!mnetor!uunet!husc6!uwvax!oddjob!mimsy!aplcen!aplcomm!aplvax.jhuapl.edu!mef
From: mef@aplvax.jhuapl.edu (Martin E. Fraeman)
Newsgroups: comp.arch
Subject: Re: Computer noises (was Re: Cray a
Message-ID: <189@aplcomm.UUCP>
Date: 6 Apr 88 02:27:51 GMT
References: <1503@vaxb.calgary.UUCP> <208300001@prism>
Sender: news@aplcomm.UUCP
Reply-To: mef@aplvax.jhuapl.edu.UUCP (Martin E. Fraeman)
Organization: The Johns Hopkins University Applied Physics Laboratory
Lines: 28
Summary: PDP 8 music in 1969

A good friend of mine (John Spies) who went to Northwestern worked on a 
PDP-8I his freshman year (1969-70).  He used the IOT instruction
to generate RF.  The IOT would cause the I/O bus drivers to 
pulldown causing a large current pulse that dominated the stray 
RF the machine was putting out.  By varying the frequency of IOT
instructions music would be picked up by an AM radio near the 
machine.  The IOT loops were timed by counting instructions which 
was easy on the early 8's because they weren't microcoded (RISC
strikes again -).  John eventually extended things to the point where it
would do 4 simultaneous voices.  Since he just stored note values and 
durations that were interpreted on the fly, a substantial amount of 
music (an entire Bach 3 part invention) could be held in the PDP-8 
4kw of memory.  I believe John also eventually wrote a graphical 
music editor to translate traditional notation into those tables.

Pretty astounding what some good assembly language programming
and a shoehorn can do on a clever machine.

	Marty Fraeman

	US Mail:	Johns Hopkins University Applied Physics Laboratory
			Johns Hopkins Road
			Laurel, Md.  20707

			301-953-5000 x8360

	Usenet:		{...allegra,seismo}!umcp-cs!aplcen!mef
	Arpanet:	mef@aplvax.jhuapl.edu