Article View: comp.arch
Article #1676Re: DECSYSTEM 20
From: Carl Lowenstein
Date: Thu, 27 Jul 1989 21:39
Date: Thu, 27 Jul 1989 21:39
28 lines
1653 bytes
1653 bytes
In article <433@scr1.UUCP> pechter@scr1.UUCP (Bill Pechter) writes:
>>In <BRUCE.89Jul23155646@heather.pooh.com> bruce@heather.pooh.com
>>(Bruce Robertson) writes:
>>> I like the way the PDP-11 treats the program counter as a general
>>> register. You can play a lot of tricks with that!
>Try this one -- toggle 014747 into memory location 10000 (or any other
>memory location in the lower 28kw). Set the pc to that location and start
>it.
>One thing of interest... I've seen it wrap through the gpr's on some
>11's but not on others. Any explanation on this would be appreciated.
Some of the medium-early 11's (11/10 and 11/05 specifically)
had a register set that was addressable on the bus by a program.
Others of earlier and later vintage did not.
Of course, all *Real* PDP-11's can read and load their
register set through the front panel lights and switches.
Nowadays, the lights and switches must cost more than
the CPU chip, so they don't make them like that.
--
carl lowenstein marine physical lab u.c. san diego
{decvax|ucbvax} !ucsd!mplvax!cdl
cdl@mpl.ucsd.edu
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wasatch!helios.ee.lbl.gov!ucsd!sdcc6!mplvax!cdl From: cdl@mplvax.EDU (Carl Lowenstein) Newsgroups: comp.arch Subject: Re: DECSYSTEM 20 Message-ID: <976@mplvax.EDU> Date: 27 Jul 89 21:39:03 GMT References: <3256@wpi.wpi.edu> <EGDORF.89Jul21195924@zaphod.lanl.gov> <443@anasaz.UUCP> <BRUCE.89Jul23155646@heather.pooh.com> <3893@phri.UUCP> <433@scr1.UUCP> Reply-To: cdl@mplvax.ucsd.edu.UUCP (Carl Lowenstein) Organization: U.C. San Diego, Marine Physical Laboratory Lines: 28