On Sun, Jul 31, 2011 at 2:26 PM, Binyamin Dissen <[email protected]> wrote: > On Sun, 31 Jul 2011 11:28:23 -0600 Paul Gilmartin <[email protected]> > wrote: > > :>The PDP-8 had no "L" (or equivalent) instruction. It was > :>necessary to synthesize it from other instructions. > > There was no native storage to register instruction? How was it done? >
Google is our friend. See: http://en.wikipedia.org/wiki/PDP-8 In essence, one cleared the accumulator then added a word (12 bits) from storage. There was an alternative in which one cleared the accumulator and ones-complemented it (one instruction) then ANDed a word from storage. I suspect the latter might have been more costly, but don't know. When one stored the accumulator, the accumulator was left full of zeros, facilitating a subsequent "load". -- Bob Netzlof a/k/a Sweet Old Bob
