What does PUSHJ do? - test-drb@ccmp.vtda.org

21 May 2005

On Thu, 12 May 2005 Allison <ajp166 at bellatlantic.net> wrote:

...
  Subject: Re:
What does PUSHJ do?
   From: Johnny Billquist <bqt at Update.UU.SE>
   Date: Thu, 12 May 2005 10:30:31 +0200 (CEST)
     To: cctalk at classiccmp.org

Not a good example. It should really be JMS FOO, and at the label FOO you
need to place a 0, which is overwritten by the return address. (What
assembler do you usually use, btw? Comments come after a slash... :-) ) 
 Mindeye.  Neumonics to octal on paper usually.  My 8 doesn't have any
 mass store not even TTY.  I plan to take some EEprom and make a RS08
 or other disk equivelent. 
Ah! That explains it. :-)

...
  Eh? No. The
PDP-8/a don't have any stack IOT. Same set as the 8/e. The
only difference is how some illegal combinations of OPR instructions act. 
 I've used one that did.  Might have been a hack.  The 6120 however does
 and the DEC purchase spec is clear on that too. It's still done with IOTs. 
Must have been some additional hardware. One brain cell seems to think
that DEC maybe sold some hardware to implement stacks on the pdp8, but it
might have been the pdp-12 as well.
But yes, the 6120 did have IOTs for that.

I have several PDP-8/A systems around, but no 6120 systems...

	Johnny

Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt at update.uu.se           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol