26 Oct
2022
26 Oct
'22
9:52 a.m.
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?…
On Wed, Oct 26, 2022 at 1:29 AM Angelo Papenhoff <aap(a)papnet.eu> wrote:
On 26/10/22, Ralph Corderoy wrote:
"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.
--
=====
nygeek.net
mindthegapdialogs.com/home <https://www.mindthegapdialogs.com/home>
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? 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