[sdiy] Messing with chips with light

[Robin Whittle]

In the "Re: [sdiy] More about IC design" thread, Dave Manley wrote:

> There's another whole interesting chapter of IC development related to
> getting a prototype chip back and what you can do to diagnose the
> failure, and to try a fix.  A process known as 'FIB'ing (Focused Ion
> Beam) allows you to basically drill down into the device and do cut and
> jumps.  Try green wiring a sub-micron design!
> 
> This is now a long way from SDIY!

Not necessarily.  I took the metal lid off the OPS chip of my Mk 1
DX7 and then focussed light onto it using a small 12v filament lamp
and a hand-held camera lens.

This would frequently crash the chip, but at one point I was able to
upset a particular part of the 1/4 sine-wave ROM, making a noisy
spike in that part of the curve, where it appeared four times per
sine-wave.

  - Robin