[TUHS] Happy birthday, PDP-8!

[TUHS] Happy birthday, PDP-8!

[Noel Chiappa]

    > From: Dave Horsfall

    > And as for subroutine calls on the -8, let's not go there...  As I dimly
    > recall, it planted the return address into the first word of the called
    > routine and jumped to the second instruction; to return, you did an
    > indirect jump to the first word.

That do be correct.

That style of subroutine call goes back a _long_ way. IIRC, Whirlwind used
that kind of linkage (alas, I've misplaced my copy of the Whirlwind
instruction manual, sigh - a real tresure).

ISTVR there was something about the way Whirlwind did it that made it clear
how it came to be the way it was - IIRC, the last instruction in the
subroutine was normally a 'jump to literal' (i.e. a constant, in the
instruction), and the Whirlwind 'jump to subroutine' stored the return address
in a register; there was a special instruction (normally the first one in any
subroutine) that stored the low-order N bits of that register in the literal
field of the last instruction: i.e. self-modifying code.

The PDP-6 (of which the PDP-10 was a clone) was on the border of that period;
it had both types of subroutine linkage (store the return in the destination,
and jump to dest+1; and also push the return on the stack).

	Noel

[TUHS] Happy birthday, PDP-8!

[Arthur Krewat]

Um. More like a natural progression.

Like 8086->80186->80286->80386->80486->...

On 3/26/2017 8:31 PM, Noel Chiappa wrote:
> The PDP-6 (of which the PDP-10 was a clone)

[TUHS] Happy birthday, PDP-8!

[Tim Bradshaw]

On 27 Mar 2017, at 01:31, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
> 
> 
> That style of subroutine call goes back a _long_ way. IIRC, Whirlwind used
> that kind of linkage (alas, I've misplaced my copy of the Whirlwind
> instruction manual, sigh - a real tresure).

This is how subroutines worked on EDSAC.  It might go back further than this, but it can't go back much further.

[TUHS] Happy birthday, PDP-8!

[Tony Finch]

Tim Bradshaw <tfb at tfeb.org> wrote:
>
> This is how subroutines worked on EDSAC.  It might go back further than
> this, but it can't go back much further.

I found this rather good survey of early subroutine linkage:
https://people.cs.clemson.edu/~mark/subroutines.html

Turing designed a stack-based linkage for the ACE, a few years before
Wheeler invented the EDSAC subroutine linkage.

Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/  -  I xn--zr8h punycode
Irish Sea: East, veering south later, 4 or 5. Smooth or slight, occasionally
moderate later in south. Showers later. Good.

[TUHS] Happy birthday, PDP-8!

[Terry Smith]

We had a PDP 8E and an 8I at Humber College back in the day. I used to 
play chess against Chekmo2 on it on paper tape.


On 2017-03-27 08:05 AM, Tim Bradshaw wrote:
> On 27 Mar 2017, at 01:31, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
>>
>> That style of subroutine call goes back a _long_ way. IIRC, Whirlwind used
>> that kind of linkage (alas, I've misplaced my copy of the Whirlwind
>> instruction manual, sigh - a real tresure).
> This is how subroutines worked on EDSAC.  It might go back further than this, but it can't go back much further..
>

[TUHS] Subroutine calling conventions - was Re: Happy birthday, PDP-8!

[Toby Thain]

On 2017-03-26 8:31 PM, Noel Chiappa wrote:
>     > From: Dave Horsfall
>
>     > And as for subroutine calls on the -8, let's not go there...  As I dimly
>     > recall, it planted the return address into the first word of the called
>     > routine and jumped to the second instruction; to return, you did an
>     > indirect jump to the first word.
>
> That do be correct.
>
> That style of subroutine call goes back a _long_ way. IIRC, Whirlwind used
> that kind of linkage (alas, I've misplaced my copy of the Whirlwind
> instruction manual, sigh - a real tresure).

This link arrived in my twitter feed this morning.
https://people.cs.clemson.edu/~mark/subroutines.html

--T

>
> ISTVR there was something about the way Whirlwind did it that made it clear
> how it came to be the way it was - IIRC, the last instruction in the
> subroutine was normally a 'jump to literal' (i.e. a constant, in the
> instruction), and the Whirlwind 'jump to subroutine' stored the return address
> in a register; there was a special instruction (normally the first one in any
> subroutine) that stored the low-order N bits of that register in the literal
> field of the last instruction: i.e. self-modifying code.
>
> The PDP-6 (of which the PDP-10 was a clone) was on the border of that period;
> it had both types of subroutine linkage (store the return in the destination,
> and jump to dest+1; and also push the return on the stack).
>
> 	Noel
>