In 1979 or so we booted our DG Nova 2 from tape by toggling in the initial bootstrap program from the front panel. This was practical because it only took a handful of instructions to tell the smart drive controller to load the first block from tape into memory at address zero, and then you just added a jump to zero. This saved us the expense of a ROM card. I had the minute or so of motions to toggle in the boot sequence memorized in my fingers like a Bach fugue.