[HECnet] DU11 vs. DUV11

[Steve Davidson]

-----Original Message-----
From: owner-hecnet at Update.UU.SE 
[mailto:owner-hecnet at Update.UU.SE] On Behalf Of Johnny Billquist
Sent: Sunday, January 06, 2013 14:51
To: hecnet at Update.UU.SE
Subject: Re: [HECnet] DU11 vs. DUV11

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.

PDT-11's, I want to say 30KB of RAM.   May 28K, it has been too long...

-Steve


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