Reversing Sinclair's 1974 calculator hack (2013)
That is so classic Sinclair. Barely working enough to be useful ("three decimal places of accuracy at best", "sin 1 takes about 7.5 seconds", and constants like pi and e are written on the case instead of fitting in ROM), but useful nonetheless, and dirt cheap.<p>Sinclair products were almost comical in how ingeniously their engineers shaved off any pennies they could. In the ZX81, the video circuit is a bizarre and extremely interesting contraption that abuses the Z80's DRAM refresh circuitry, and on the mechanical side only two screws hold down the PCB to the case, despite there being many more intended screw holes in both PCB and case (someone must have figured out that hey, it still holds in place with two).<p>I have marveled a lot at what the engineers came up with, and cursed at it just as much.<p>For the ZX81's ingenious video circuit and sleek case, you get a device with chips that get dangerously (literally painfully) hot, and most CPU time used for drawing the screen--without the ability to set individual pixels in <i>any</i> way. The keyboard "cable" plugged into the PCB is just an extension of the paper-like foil that makes up the terrible, terrible keyboard, and that can easily self-destruct when disassembling your ZX81: The foil does not like any amount of bending, including the bending when you fold the case open.<p>I could go on an on about how clever Sinclair's engineering was to barely stay past the line of what makes a working product so brilliantly.