[HECnet] DU11 vs. DUV11

[Johnny Billquist]

On 2013-01-06 18:13, Lee Gleason wrote:

              .IF DF   L$$SI1

              MOVB       @(R5)+,-(SP)       ;;; COPY CHARACTER FOR WORD MOVE
MOV         (SP)+,(R4)           ;;;   (SAVES 85 USECS ON PDT-11)

              .IFF       ; DF L$$SI1

              MOVB       @(R5)+,(R4)         ;;; OUTPUT A CHARACTER

              .ENDC     ; DF L$$SI1

OK, I'll bite.   Why is moving a character in the deferred location in
R5 to the stack and then, from the stack to the address in R4 faster
than just going from the deferred R5 location to the R4 address?
--

  I'm even more curious what a PDT-11 optimization is doing in an RSX
driver...was there at one time an RSX product product planned for the
PDT family?

I'm not at all surprised to learn that RSX ran on the PDT-11.
RSX can run on pretty much any PDP-11, as long as you have atleast around 50K of ram. That's about the lower limit, I'd guess. No other hardware frills or features required.

I'm curious if the PDT-11 supported booting over the DUV-11. That would have made it a pretty nice netbooted, diskless RSX machine. Otherwise I'd suspect the most common use was just 11S booted from whatever locally. But an unmapped 11M system is a possibility, I guess.

	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