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Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!ihnp4!fortune!mbr
From: mbr@fortune.UUCP
Newsgroups: net.jokes
Subject: Re: Re: Assembler Manual Needed - (nf)
Message-ID: <2828@fortune.UUCP>
Date: Fri, 23-Mar-84 19:04:57 EST
Article-I.D.: fortune.2828
Posted: Fri Mar 23 19:04:57 1984
Date-Received: Sun, 25-Mar-84 09:39:45 EST
Sender: notes@fortune.UUCP
Organization: Fortune Systems, Redwood City, CA
Lines: 36

#R:pucc-i:-20600:fortune:5400086:000:983
fortune!mbr    Mar 23 13:36:00 1984

Aw, c'mon!  How about the PDP-11's clear core in one instruction.
First toggle (remember when computers had switch registers) in the
following two words.  Then load R0 with the address of the first
location past the top of memory.  Load the PC (a.k.a. R7) with 0
and run the code.

Addr    Value   Instruction
000000	015750	MOV @(R7)-, @(R0)-
015750	000000  .WORD 0

The PDP-8 code to clear a whole memory bank including the code
itself was even more fun, but who programs PDP-8's nowadays.
For those who remember:

0004	1005	TAD 5
0005	3410	DCA I 10
0006	5004	JMP 4
0007	5404	JMP I 4
0010	0011	11
0011	2010	ISZ 10

If you gotta ask, you just don't know!


		{allegra,amd70,cbosgd,dsd,dual,
		 harpo,hpda,ihnp4,megatest,nsc,
		 oliveb,sri-unix,twg,varian,VisiA,wdl1}!fortune!mbr


PS - If anyone cares, I'll follow with an explanation of the approx. 4
     passes through memory this takes to get around to clearing everything,
     assuming you already know PDP-8 machine language.