3 ms·

Back when computers had front panels full of lights they would often make pretty patterns with the lights when they had nothing else to do. One of the fun thin

Back when computers had front panels full of lights they would often make pretty patterns with the lights when they had nothing else to do. One of the fun things about building a recreation of the PDP-11/70 is to watch the idle display when RSX-11M+ isn't doing anything.

segfaultbuserr 4y ago
The RT-11 operation system for the PDP-11 was filled with amusing quotations all over the kernel source code. The following is the source code of the CPU idle loop routine, with blinkenlights [0]. Note the funny quotations, and also note the use of self-modifying code - light direction reversal was implemented by overwriting the ROL/ROR instruction dynamically. ; "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" ; "I got plenty of nothin', and nothin's plenty fo' me!" ; - George and Ira Gershwin, "Porgy and Bess" ;- 30$: .IF NE LIGH$T DEC (PC)+ ;The RT-11 lights routine! LITECT: .WORD 1 BNE ..NULJ ;Not too often ADD #<512.>,LITECT ;Reset count, clear carry 40$: ROL 70$ ;Juggle the lights BNE 50$ ;Not clear yet COM 70$ ;Turn on lights, set Carry 50$: BCC 60$ ;Nothing fell off, keep moving ADD #<100>,40$ ;Reverse direction BIC #<200>,40$ ;ROL/ROR flip 60$: BIT #<LIGHT$>,CONFG2 ;Does CPU have a light register? BEQ ..NULJ ;No MOV (PC)+,@(PC)+ ;Put in lights (for 11/45) 70$: .WORD 0, SR .ENDC ;NE LIGH$T If the code doesn't detect a light register, it runs the following NOP loop instead. ..NULJ:: .IF EQ RTE$M ;;; WAIT ;Nothin' to do, so don't NOP ;Nothin' to do, so don't .IFF ;EQ RTE$M NOP ;Let the host do the waiting .ENDC ;EQ RTE$M NOP ;Second pad instruction .BR SCNALL ;Drop into ready job scan loop setup [0] http://www.kpxx.ru/DEC/PDP-11/Software/OS/RT-11/05.07/05.07.abl/Unpacked/RMON.MAC http://www.kpxx.ru/DEC/PDP-11/Software/OS/RT-11/05.07/05.07....

segfaultbuserr 4y ago

The RT-11 operation system for the PDP-11 was filled with amusing quotations all over the kernel source code. The following is the source code of the CPU idle loop routine, with blinkenlights [0]. Note the funny quotations, and also note the use of self-modifying code - light direction reversal was implemented by overwriting the ROL/ROR instruction dynamically. ; "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" ; "I got plenty of nothin', and nothin's plenty fo' me!" ; - George and Ira Gershwin, "Porgy and Bess" ;- 30$: .IF NE LIGH$T DEC (PC)+ ;The RT-11 lights routine! LITECT: .WORD 1 BNE ..NULJ ;Not too often ADD #<512.>,LITECT ;Reset count, clear carry 40$: ROL 70$ ;Juggle the lights BNE 50$ ;Not clear yet COM 70$ ;Turn on lights, set Carry 50$: BCC 60$ ;Nothing fell off, keep moving ADD #<100>,40$ ;Reverse direction BIC #<200>,40$ ;ROL/ROR flip 60$: BIT #<LIGHT$>,CONFG2 ;Does CPU have a light register? BEQ ..NULJ ;No MOV (PC)+,@(PC)+ ;Put in lights (for 11/45) 70$: .WORD 0, SR .ENDC ;NE LIGH$T If the code doesn't detect a light register, it runs the following NOP loop instead. ..NULJ:: .IF EQ RTE$M ;;; WAIT ;Nothin' to do, so don't NOP ;Nothin' to do, so don't .IFF ;EQ RTE$M NOP ;Let the host do the waiting .ENDC ;EQ RTE$M NOP ;Second pad instruction .BR SCNALL ;Drop into ready job scan loop setup [0] http://www.kpxx.ru/DEC/PDP-11/Software/OS/RT-11/05.07/05.07.abl/Unpacked/RMON.MAC http://www.kpxx.ru/DEC/PDP-11/Software/OS/RT-11/05.07/05.07....