Imagesource: http://blog.notdot.net/

FPGAs have a certain magic in their own right. On the one hand, they cannot be compared with CPUs or microcontrollers, even if they ultimately simulate them. On the other hand, they have the advantage over ASICs, that they can be reconfigured - allowing you to cast virtually any of your own designs into hardware.

How exactly an FPGA makes this possible, is an exciting question. The answer to which can be found in many thick books on information technology and computer science. If you don't feel like studying books and are looking for a shortcut, the following may help.

Nick Johnson has (admittedly already several years ago) accepted the challenge to build his own mini-FPGA based on LS7400 chips.

His project does inspire despite its age and is no less up to date. In a short demo video Nick tests two configurations and solves different problems in hardware. Impressive.

Certainly, this is no option to build a fully fledged FPGA based on the 74XX’s, but testing and understanding the basic principles with it, is definitely real fun.