Computer bending

Computer Bending

Yes, it is possible. I always wondered what would happen if you start circuit bending a computer. The obvious answer is that it will crash. Indeed it is not very good to cross pins on the motherboard. However this does not always hold true for the Video ram chips. My original idea was to start bending the video inpired by some Nintendo Cart bending that I have seen. The ISA video card which I began experimenting with had 512kb chips in individual sockets. The initial exploration yielded interesting results, scrambled video, aliasing, noise. Great!

Drunk on my success I darengly proceeded to explore the sacred onboard video chips looking for video distortions. With an LED light probe I noticed that certain pins produced pulsating varying in the brightness of the LED as different objects were being displayed in the screen. I wondered if you could hear these variations and indeed you can.
Sound Sample 1
Sound Sample 2
Sound Sample 3

Truly an incredible number of audio/video bends exists on the motherboard. In this experiment I stopped at 28. It is a good idea to use an eyelit board or some sort of an intermediary tap for the bend points. The connections are hard to solder very well, due to their size as well as the heat damage that may result from using too much solder. If the connections are not attatched very well they will not handle mointing of switches and occasional tugs.

After a long and drawn out process of listening to alot of points on the motherboard, I decided to just pick a couple of dosen based on the different sounds which they produced.

As an easy way to switch between different points I chose to use 12 pole and a 6 pole rotary switches ( because of avaliability ). The bends were distributed among the switches however one aspect is critical when it comes to arranging the bends.
Test bends as you go. Rotary switches short the contacts located next to each other as you turn the pole. This will create crashes unless arranged properly, in which case it will create a video bend. Like the ones shown above.

What to do with all those audio/video bend points is entirely up to the builder.
In my case I chose to make a few extra circuits to further process the sound. Several op-amps can be used to boost the signal, as well as shape it in different ways like summing, subrtacting, inverting, or clipping.
In my case the circuit was very simple. One quad op-amp, 5 resistors and a capacitor.
The schematic shows the wiring of the patch switches to the op amp circuits. Points at the bottom represent the incoming connections and the top is the amplifier left and right channels.

The combination of video and audio bending produces interesting results which are indeed closelly tied together. One does not seem right without the other.

Finished Unit 1.

More info and video clips will be up soon. This is just a teaser post. Complete how to will be avaliable.