Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!bu-cs!bloom-beacon!usc!eve.usc.edu!mlinar
From: mlinar@eve.usc.edu (Mitch Mlinar)
Newsgroups: comp.misc
Subject: Re: Laptops and Airports
Message-ID: <17061@usc.edu>
Date: 6 May 89 22:07:09 GMT
References: <39382@bbn.COM>
Sender: news@usc.edu
Reply-To: mlinar@eve.usc.edu (Mitch Mlinar)
Organization: University of Southern California, Los Angeles, CA
Lines: 33

In article <39382@bbn.COM> cosell@BBN.COM (Bernie Cosell) writes:
>
>In particular: CAN the metals detectors harm microcircuits?  How about the
>xray machine... can zapping a laptop hurt it?  Does the answer change if the
>laptop has, say, an internal hard disk?
>

Floppies and such are unlikely to be affected by the low level of magnetics
on the walk-through detecter.  Probably even less by the X-ray.  Both tapes
and floppies have traveled this route numerous times with no problem.

On the other hand, many laptops have older CMOS EPROMs which are affected -
over time - by X-ray.  The result *IS* cumulative as each time you get it
X-rayed, it increases the floating gate charge a "tad".  What that "tad" is,
I do not think has been measured and is likely to depend upon a whole bunch
of other factors (initial gate charge, temperature, etc.)

I have only one data point: after having an Epson for six months, my friend
started to travel with it.  After the 11th trip through X-ray, the machine
broke.  Fortunately, he had read all of the machines CMOS EPROMs shortly
after purchase (4 of them).  He burned a whole new set and swapped one at a
time on the chance that it was the EPROM; he found the offending one.  It has
been a year since of the same air travel, but the machine is always hand
checked now.  No other problems have occurred.

As someone else pointed out, other chips which do not have floating gate
charges (uP and other logic) are not likely to be affected.

I understand that newer CMOS EPROMs are "sturdier" (higher floating gate
voltage?) and, thus, are not QUITE as finicky.  However, given that hand
check takes a good minute extra, I do not take the X-ray risk.

-Mitch