Re: Diff between 11/20 and 11/45

There is huge difference between the machines, but not backwards! The 11/20 doesn't have :- EIS instructions like div, mul, ash etc FPU instructions like fmul ... MMU no memory management of any sort, 56Kb memory, 8Kb I/O page and hence no user modes, 16 bit addressing So a program written for a 11/20 should work untouched on an 11/45 except for some very minor (and ugly) instruction sequences involving using the same register for both source and destination eg mov r2,-(r2), or jmp (r2)+. The behaviour of the trace trap and T bit is also different. There is a list of differences some some of the PDP/11 handbooks (perhaps the latter architecture book). Received: (from major@localhost) by minnie.cs.adfa.edu.au (8.9.3/8.9.3) id KAA03319 for pups-liszt; Wed, 8 Sep 1999 10:38:29 +1000 (EST) Received: from caveman.geac.com.au (caveman.geac.com.au [203.30.73.2]) by minnie.cs.adfa.edu.au (8.9.3/8.9.3) with SMTP id KAA03314 for &lt;pups(a)minnie.cs.adfa.edu.au&gt;; Wed, 8 Sep 1999 10:38:20 +1000 (EST) Received: (qmail 4222 invoked from network); 8 Sep 1999 10:56:15 +1000 Received: from trowel.geac.com.au (203.1.26.189) by caveman.geac.com.au with SMTP; 8 Sep 1999 10:56:15 +1000 Received: (qmail 27184 invoked from network); 8 Sep 1999 11:04:35 +1000 Received: from fgh.geac.com.au (202.6.67.163) by trowel.geac.com.au with SMTP; 8 Sep 1999 11:04:35 +1000 Received: from localhost (dave@localhost) by fgh.geac.com.au?r with ESMTP id KAA21475 for &lt;pups(a)minnie.cs.adfa.edu.au&gt;; Wed, 8 Sep 1999 10:50:40 +1000 X-Envelope-From: dave(a)horsfall.org X-Envelope-To: &lt;pups(a)minnie.cs.adfa.edu.au&gt; X-Authentication-Warning: fgh.geac.com.au: dave owned process doing -bs Date: Wed, 8 Sep 1999 10:50:39 +1000 (EST) From: Dave Horsfall &lt;dave(a)fgh.geac.com.au&gt; X-Sender: dave@fgh To: PDP Unix Preservation Society &lt;pups(a)minnie.cs.adfa.edu.au&gt; Subject: Re: KE11-A! (was Diff between 11/20 and 11/45?) In-Reply-To: &lt;199909070110.LAA12638(a)henry.cs.adfa.edu.au&gt; Message-ID: <Pine.GSO.4.10.9909081049430.19899-100000@fgh> X-No-Archive: Yes X-Witty-Saying: "Tesseract - Enter at own risk" X-Disclaimer: "Me, speak for us?" MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-pups(a)minnie.cs.adfa.edu.au Precedence: bulk On Tue, 7 Sep 1999, Warren Toomey wrote: Yep; I read through my own 11/20 handbook, and I remembered that EAE weirdness. -- Dave Horsfall VK2KFU dave(a)geac.com.au Ph: +61 2 9978-7493 Fx: +61 2 9978-7422 Geac Computers P/L (FGH Division) 2/57 Christie St, St Leonards 2065, Australia Received: (from major@localhost) by minnie.cs.adfa.edu.au (8.9.3/8.9.3) id KAA03361 for pups-liszt; Wed, 8 Sep 1999 10:43:07 +1000 (EST) Received: from moe.2bsd.com (0(a)MOE.2BSD.COM [206.139.202.200]) by minnie.cs.adfa.edu.au (8.9.3/8.9.3) with ESMTP id KAA03354 for &lt;pups(a)minnie.cs.adfa.edu.au&gt;; Wed, 8 Sep 1999 10:42:59 +1000 (EST) Received: (from sms@localhost) by moe.2bsd.com (8.9.0/8.9.0) id RAA15948 for pups(a)minnie.cs.adfa.edu.au; Tue, 7 Sep 1999 17:49:36 -0700 (PDT) Date: Tue, 7 Sep 1999 17:49:36 -0700 (PDT) From: "Steven M. Schultz" &lt;sms(a)moe.2bsd.com&gt; Message-Id: &lt;199909080049.RAA15948(a)moe.2bsd.com&gt; To: pups(a)minnie.cs.adfa.edu.au Subject: Re: Diff between 11/20 and 11/45? Sender: owner-pups(a)minnie.cs.adfa.edu.au Precedence: bulk Similarily MOV R0,(R0)+ won't work as expected on some 11s. I suspect that the even less likely case of "mov pc,-(pc)" won't work either :-) Fairly common when setting up call frames, etc. You want the address of where the arguments start and since they're pushed on the stack 'sp' is the value you want. There's a comment in 2BSD (I think it came from V7) where mention is made that "we can't do sp,-(sp) because it won't work on the 11/40". Hmmm, interesting. The workaround I saw took an extra instruction. Steven Schultz sms(a)moe.2bsd.com Received: (from major@localhost) by minnie.cs.adfa.edu.au (8.9.3/8.9.3) id KAA03462 for pups-liszt; Wed, 8 Sep 1999 10:53:48 +1000 (EST)