RT-11 is "famous" for self-modifying code. That fact makes it so much fun to debug when you have a real-time bug. Been there... Done that... -Steve -----Original Message----- From: owner-hecnet at Update.UU.SE [mailto:owner-hecnet at Update.UU.SE] On Behalf Of Johnny Billquist Sent: Monday, June 04, 2012 22:52 To: hecnet at Update.UU.SE Subject: Re: [HECnet] Speaking of IDLE On 2012-06-05 04:44, Johnny Billquist wrote: On 2012-06-05 03:24, Steve Davidson wrote: Paul, I think that depends on whether or not the idle loop pattern (for the console light display) is being used. The lights pattern most certainly makes use of the WAIT instruction. The SJ monitor is a completely different beast than FB and friends - no question about it! Well, there are more ways to spin a cat... Or spin the lights in this case. WAIT is one way to show something on the front panel. Loading the display register is another. RT-11 is in fact using the Switch Register at 177570 to display things on the front panel. Look at RMONFB.MAC, around line 4800, to see the code. (Every time I read the RT-11 sources, I feel a little dirty... No offense meant for the RT-11 fans around here or anywhere.) It's all conditionalized on LIGH$T, and there is not even the option if you are running the SJ monitor... Aw, heck. I might as well post the code, since isn't that long... ==== 3$: .IF NE LIGH$T .ROM DEC LITECT,VALUE=1 BNE 8$ ADD #512.,LITECT 4$: ROL 7$ BNE 5$ COM 7$ 5$: BCC 6$ ADD #100,4$ BIC #200,4$ 6$: BIT #LIGHT$,CONFG2 BEQ 8$ MOV (PC)+,@(PC)+ 7$: .WORD 0,SR .ENDC 8$: ..NULJ:: ==== (And yes, SR is defined as 177570) (And maybe you understand why I feel dirty when reading RT-11 after this fine example of code... It's cut-and-pasted right from the source, it really looks just like this.) Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt at softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol