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[Thomas DeBellis]

I am trying to remember the lights on the 11's that I used; these are in 
the 1978-1981 time frame.  WPI had an 11/45 with a (NICE!) GT40 in 
mechanical engineering which ran RT-11.  I remember that busy looping.  
The computer science department had a (mighty) 11/05 which ran a couple 
of things:

  * RT, looping (lots of blinky)
  * Unix, can't remember as we almost never ran it.  It was pretty much
    a curiosity and the terminal handling of the time was thoroughly
    despised.
  * RSX, not so much blinky

Columbia had a very nice 11/45 which ran RSTS which didn't blink so 
much.  11/40's (which were the front-end's for the 20's) ran a version 
of RSX called 20F (Johnny can speak to it better than I can).  For 
Tops-20 3A, it didn't have much to do as the DH's handled a bit of the 
buffering, so it didn't blink so much.  From version 4 on, it had to 
handle smooth scrolling which broke everything; it had to do continuous 
polling to looking for ^S's, which the hardware would not pause on.  
Lots of blinky, which was a shame because you used to be able to open 
the door and could guess at how many users you had by looking at the 
lights for 3A.

The DN20's ran either MCB (DECnet) or DN60 (IBM bisynch 
communications).  However, these were 11/34's which couldn't even do 
blinky.  I don't know how MCB idle's; I don't think we had source.

We did have source for the DN60, which I was responsible for being the 
Galaxy dude.  The DN60 appears to be written from scratch, but some of 
it strikes me as possibly being from RSX.  It had a three level 
'friendly' round-robin scheduler (I.E., no preemption).  Basically, the 
idle task either updates various clocks, checking for certain conditions 
or it loops checking to see if any tasks can be run.  I would predict 
that, were it to be run on something with a bit display, that there 
would be a lot of blinky.

;
; SUBROUTINE CALLED BY THE DISPATCHER WHEN ALL TASKS ARE WAITING.
;
DSPIDL: INC     DSPMTY          ;NOTE DISPATCHER IDLE CYCLE
         BVC     11$             ;BRANCH IF NO OVERFLOW
         STOPCD  WDG             ;CLOCK HAS STOPPED TICKING
11$:    CMP     DSPCLK,JIFCLK   ;IS THE DISPATCHER CLOCK UP TO DATE?
         BNE     12$             ;NO.
         RTS     PC              ;YES, CHECK ALL TASKS AGAIN.

Those quotes are great; I don't remember anything like that in DN60.
> ------------------------------------------------------------------------
> On 10/1/21 9:00 PM, Paul Koning wrote:
>
>
> That's what I thought but that's only half correct.  RT-11 SJ does busy looping; RT-11 FB has an idle task that includes a wait instruction (which is how it gets the rotating lights pattern -- the difference with other OSs is that it sets the pattern into the display register rather than into R0).
>
> ; "A SOURCE OF INNOCENT MERRIMENT!"
> ;	- W.S. GILBERT, "MIKADO"
> ; "DID NOTHING IN PARTICULAR, AND DID IT VERY WELL"
> ;	- W.S. GILBERT, "IOLANTHE"
> ; "TO BE IDLE IS THE ULTIMATE PURPOSE OF THE BUSY"
> ;	- SAMUEL JOHNSON, "THE IDLER"
>
> 10$:	DEC	(PC)+		;THE RT-11 LIGHTS ROUTINE!
> 20$:	1
> 	BNE	14$		;NOT TOO OFTEN
> 	ADD	#512.,20$	;RESET COUNT, CLEAR CARRY
> 16$:	ROL	13$		;JUGGLE THE LIGHTS
> 	BNE	11$		;NOT CLEAR YET
> 	COM	13$		;TURN ON LIGHTS, SET CARRY
> 11$:	BCC	12$		;NOTHING FELL OFF, KEEP MOVING
> 	ADD	#100,16$	;REVERSE DIRECTION
> 	BIC	#200,16$	;ROL/ROR FLIP
> 12$:	MOV	(PC)+,@(PC)+	;PUT IN LIGHTS
> 13$:	.WORD	0,SR
> 14$:	MOVB	#MXJNUM/2+200,INTACT ;DO A COMPLETE SCAN
> EXUSLK:	BR	EXUSER		;BACK INTO LOOKFOR LOOP
>
> 	paul
>> ------------------------------------------------------------------------
>> On Oct 1, 2021, at 8:54 PM, Johnny Billquist <bqt at softjar.se> wrote:
>> Also for RSX. Basically, they both use WAIT, and that's all that is required from simh. RT-11 is busy-looping, though.
>>> ------------------------------------------------------------------------
>>> On 21-Oct-01 15:25, Paul Koning wrote:
>>>
>>> Yes for RSTS, I don't remember RSX, and I don't think so for RT11.
>>>> ------------------------------------------------------------------------
>>>> On Oct 1, 2021, at 4:00 AM, Brian Hechinger <wonko at 4amlunch.net> wrote:
>>>>
>>>> Man I wish we weren't on the Amber list. Such a hassle to travel there right now.
>>>>
>>>> I should get simh fired up on the NUC. I'm thinking something PDP-11 and then maybe..... RSX? I don't even know what I'd want to run.
>>>>
>>>> Does the PDP-11 stuff properly do idle? The NUC is pretty powerful, why not run several PDP-11s? :-D
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