Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!ames!sparkyfs.erg.sri.com!hercules!fernwood!portal!cup.portal.com!thad
From: thad@cup.portal.com (Thad P Floryan)
Newsgroups: comp.sys.amiga
Subject: Re: Blowing up your 1950
Message-ID: <36456@cup.portal.com>
Date: 2 Dec 90 08:18:54 GMT
References: <964.2754A82B@weyr.FIDONET.ORG>
Organization: The Portal System (TM)
Lines: 30

David.Plummer@f70.n140.z1.FIDONET.ORG (David Plummer)
in <964.2754A82B@weyr.FIDONET.ORG> writes:
 
	[...]
	Point being, nothing can instantly destroy your monitor.  Even if you
	could damage it, I don't think anything could be so severe as to do
	damage before you could turn it off.

On the early IBM-PCs (and maybe still for all I know about "those" systems),
it was possible to change video attributes by altering the values written to
the registers in the video controller chip.  An errant program (or a malicious
Trojan Horse) could also change the value in the register all the way down to
ZERO.  Just imagine what used to happen when, say, an expected 15KHz AC signal
on the CRT coil(s) is now pure DC.  Yes, it WOULD and DID destroy the CRT.

*PO*O*F*

On the Amiga, we see numerous instances in this newsgroup about the battery-
backed clock getting clobbered by errant programs ... the clock's registers
are sitting in the address space easily touchable by any program.

And guess what ALSO is vulnerable to errant programs:  your SCSI interface.

Does anyone STILL doubt the value of an MMU to protect one's system and other
processes?

Protection not only from "normal" programming bugs during development, but
from virii such as the LAME-BRAINER or whatever?

Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com!thad ]