From: "Michael A. Terrell"
Subject: Re: Upsidedown EPROMS
Date: Wed, 02 Oct 2002 13:43:55 -0400
Organization: I'm trying!
X-Mailer: Mozilla 4.61 [en]C-CCK-MCD (Win95; U)
> Have a look at http://www.thatswatt.com/electron/hintsele.html about
> the Upsidedown EPROM "Hint". Have you ever seen this applied? Are
> there any other ways that are better to protect the software in an
> EPROM? IŽd be interested to hear your thoughts.
Why bother? Bending the leads that far may not break them right
away, but they will loose a lot of strength and may crack later. Some
places I've worked did not allow you to straighten leads on chips if
they were very far out of alignment. For reliability you had to put in a
new part and write the part off as damaged.
There are better ways to protect the code from casual inspection, or
I have seen sockets that made to install the chip upside down
Wire an adapter to move the data lines around, and do the same with
the address lines. It will list as total garbage. Just lay out the
board to match the adapter, and the chip will give the right data, at
the right address. This was used in a clone of the Commodore 1541
floppy disk drive. They "Guaranteed 100% software compatibility to the
1541". Of course it was compatible, they read the Commodore chips,
scrambled the data and address lines and burnt their EPROMs.
A quick look at the circuit board proved what they did, but their
intent was clear. If they were taken to court over infringement, their
EPROMs were in no way the same when disassembled. I used software that
read the ROMs in the drives, and found that every bit matched, at every
Also, the site is annoying with all the Flash, and pages that take
minutes to load, only to display a black bar when complete.
Michael A. Terrell