Peter Capek found this obit of John Griffith. Indirect addressing patent, for whatever it’s worth. https://www.legacy.com/us/obituaries/bradenton/name/john-griffith-obituary?id=34037343 On Wed, Oct 26, 2022 at 1:29 AM Angelo Papenhoff wrote: > On 26/10/22, Ralph Corderoy wrote: > > > Before these instructions, a subroutine call would require one > > > additional memory location, to hold the return address for each point > > > of call, and one additional instruction, one to load the return > > > address into the accumulator and one to store it into the code at the > > > end of the subroutine. (The latter could be the first instruction of > > > the subroutine.) > > > > So before SP and TA, would the ‘latter’ instruction at the start of the > > subroutine, which stores the accumulator holding the return address, be > > modifying all sixteen bits of the location unlike TA which only modifies > > the bottom eleven? > > "Before" sounds a bit misleading. The Whirlwind ran its first actual > program > (from test storage, i.e. 27 switch and 5 flip-flop registers) in late 1949, > so the change we're talking about here was early enough that the old way > of doing jumps was only ever theoretical. > Still, there was from the start a td (transfer digits) instruction, > which stores the address bits from AC into the addressed location. ta is > much the same except it stores A. > > > If so, did the accumulator's top bits hold the ‘return’ op-code or was > > there another instruction near the subroutine's end which loaded the > > 11-bit address before a second instruction jumped to it? > > Without ta, a subroutine jump could be done like this: > > ca reta ; load return address > sp foo ; jump to foo > ret, ... ; return here > > foo, td foo1 ; store return address > ... ; do stuff > foo1, sp . ; return from here > > reta, ret > > Of course then you lose the possibility of passing some argument in AC. > > Cheers, > aap > -- ===== nygeek.net mindthegapdialogs.com/home