Low-level machine hacks can be inscrutable even when the machine they're implemented for is current. For instance, there's the infamous line from Quake source code that reads:

    i  = 0x5f3759df - ( i >> 1 ); // what the fuck?

People have tried to investigate the origin of this baffling hack and mostly failed. See, e.g., http://www.beyond3d.com/content/articles/8/ .