From: Larry Stewart <stewart@serissa.com>
To: Ralph Corderoy <ralph@inputplus.co.uk>
Cc: tuhs@tuhs.org
Subject: [TUHS] Re: who invented the link register
Date: Wed, 26 Oct 2022 07:12:40 -0400 [thread overview]
Message-ID: <03E1CE6B-6112-4EAB-BFE1-E5AFC0A2075B@serissa.com> (raw)
In-Reply-To: <20221026044530.1DAC22033C@orac.inputplus.co.uk>
Whirlwind I had a TD (transfer digits) instruction that stored only the low 11 bits from the accumulator to storage
> On Oct 26, 2022, at 12:45 AM, Ralph Corderoy <ralph@inputplus.co.uk> wrote:
>
> Hi Lawrence,
>
>> With the new SP and TA, one would use SP to call a subroutine, and the
>> first instruction of any subroutine would be TA to save the return
>> address into the final location of the subroutine. (TA only modified
>> the low 11 bits of the 16 bit location)
>>
>> 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?
>
> --
> Cheers, Ralph.
next prev parent reply other threads:[~2022-10-26 11:12 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-12 19:01 [TUHS] " ron minnich
2022-10-24 23:46 ` [TUHS] " Angelo Papenhoff
2022-10-25 8:35 ` Angelo Papenhoff
2022-10-25 17:00 ` Lawrence Stewart
2022-10-25 18:26 ` Clem Cole
2022-10-25 20:05 ` Marc Donner
2022-10-25 21:03 ` Lawrence Stewart
2022-10-26 4:45 ` Ralph Corderoy
2022-10-26 5:29 ` Angelo Papenhoff
2022-10-26 7:52 ` Marc Donner
2022-10-26 11:12 ` Larry Stewart [this message]
2022-10-25 22:24 ` Bakul Shah
2022-10-25 22:41 ` Harald Arnesen
2022-10-25 22:47 ` Robert Clausecker
2022-10-25 22:52 Noel Chiappa
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