Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!gatech!hao!husc6!necntc!necis!encore!collins From: collins@encore.UUCP (Jeff Collins) Newsgroups: comp.sys.nsc.32k Subject: Re: cxp/rxp instructions Message-ID: <1751@encore.UUCP> Date: Mon, 13-Jul-87 09:54:06 EDT Article-I.D.: encore.1751 Posted: Mon Jul 13 09:54:06 1987 Date-Received: Tue, 14-Jul-87 06:09:58 EDT References: <10742@hi.UUCP> Organization: Encore Computer Corp., Marlboro, MA Lines: 20 Keywords: rxp/cxp instructions Summary: cxp/rxp instructions In article <10742@hi.UUCP>, cyrus@hi.UUCP (Tait Cyrus) writes: > Here at the University of New Mexico, we will be starting to port > GENIX 4.2 to a 32016/32032 board. I have some questions. > > 1) What good are the cxp/rxp instructions? > 2) Why can't the "standard" jsr/ret instructions be used? > 3) What advantages are there for going through a jump table instead > of jumping directly? > In normal operation these instructions should NOT be used. They are much slower than jsr/ret. We changed our compiler to not generate these instruction do to thier execution times. In fact we modified the OS to use the MOD register as infrequently as possible (only on interrupts, where we have no control over the CPU using it). The next National chip (32532) has a direct interrupt mode that does not go through the MOD table to find its vector. We will be using that when we upgrade...