Hardware

AppleCrate II: A New Apple II-Based Parallel Computer

The AppleCrate II is made from 17 Enhanced Apple //e main boards. (Fifteen of these boards were obtained in the same eBay auction that netted the eight unenhanced boards for the original AppleCrate.) Because they are enhanced ROMs, the original NadaNet boot ROM code would not fit and a new boot protocol had to be developed, as described below.

Instead of mounting the cards vertically in a frame, as in the original, I decided to mount them horizontally in a stack secured with standoffs—3/4" long hexagonal rods, each with a screw protruding from one end and a tapped hole in the other. The AppleCrate II has nine "columns" of these standoffs—six metal columns at the back and corners of the boards and three nylon columns interior to the boards to add stiffness[...]

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This has got to be one of the coolest hacks I've seen in a very long time. I will always have a fondness for the Apple II series; not the least of which because it's based on the MOS Technologies 6502 microprocessor.

It's well worth hitting the link just to see a picture of this rig. It's really cool looking.
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The boards are powered by a PC AT power supply. The average power consumed by an Apple //e board is about 4.2 watts, so the whole 17-board crate consumes only about 70 watts in total, and both the AppleCrate and the power supply run only a few degrees above ambient temperature.