[Info-vax] OT: PDP-11 history in arstechnica

[chris]

On 03/15/22 02:18, Rich Alderson wrote:
> chris<chris-nospam at tridac.net>  writes:
>
>> On 03/15/22 01:22, Simon Clubley wrote:
>>> On 2022-03-14, Bob Gezelter<gezelter at rlgsc.com>   wrote:
>>>> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
>>>>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
>
>>>> Arne,
>
>>>> Not sure where the author of the arstechnica piece saw "$" for immediate
>>>> mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#", e.g., MOV
>>>> #SS.XYZ,R0.
>
>>>> Spent lots of time writing and generating assembler for RSX-11 systems and
>>>> relatives, e.g., P/OS. Did many interesting things.
>
>>>> - Bob Gezelter, http://www.rlgsc.com
>
>>> DEC versus AT&T syntax (and yes, I know the following is Intel not DEC,
>>> but it's much the same thing here for the syntax you mention):
>
>>> https://wiki.osdev.org/Opcode_syntax
>
>>> Perfectly normal and expected. Also note "mov src, dest" instead of
>>> "mov dest, src".
>
>> Yes, from, to, left to right. Same for 68000 series as well. Intel
>> always were a bit backward in that respect...
>
>>> Expect to see more of it in your future. :-)
>
> "DEC" syntax, hmm?  Macro-10:
>
> 	MOVE 17,SUMWHR
> 	ADDI 17,37
> 	MOVEM 17,ELSWHR
>
> The "destination" AC always follows the opcode immediately, the effective
> address of the "source" comes after the comma.  Note that since there are
> "to-memory" instructions, the notion of "source" vs. "destination" is not
> particularly useful...
>

Perhaps, but people no longer program in octal, nor have to worry about
where the opcode field etc is in the instruction stream. Not familiar
with Macro-10 syntax, but assume that would be source -> destination as
well.

Just saying, read left to right, move something from a source to a
destination, so the dec pdp11 macro syntax is more natural. Having
worked with a lot of micros, some of which are quite primitive and
badly thought out, the PDP11 was light years ahead. Instructions
like sob, to create a tight loop in 3 lines of macro were truly
revolutionary and being of the sixties, always wondered what
those guys must have been smoking...

Chris