From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 103992 invoked by alias); 17 Aug 2016 18:35:22 -0000 Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org Received: (qmail 103907 invoked by uid 89); 17 Aug 2016 18:35:21 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.9 required=5.0 tests=BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_DNSWL_NONE autolearn=no version=3.3.2 spammy=HTo:D*gentoo.org, HTo:D*jp, pin X-HELO: p3plwbeout03-05.prod.phx3.secureserver.net Received: from p3plsmtp03-05-2.prod.phx3.secureserver.net (HELO p3plwbeout03-05.prod.phx3.secureserver.net) (72.167.218.217) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 17 Aug 2016 18:35:11 +0000 Received: from localhost ([72.167.218.131]) by p3plwbeout03-05.prod.phx3.secureserver.net with bizsmtp id YJbA1t0042qhQio01JbADz; Wed, 17 Aug 2016 11:35:10 -0700 X-SID: YJbA1t0042qhQio01 Received: (qmail 19681 invoked by uid 99); 17 Aug 2016 18:35:10 -0000 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" User-Agent: Workspace Webmail 6.4.6 Message-Id: <20160817113508.5c1bb9f86d671edec44bb378f25c04cc.5ecda5525d.wbe@email03.godaddy.com> From: To: "Mike Frysinger" , "ISHIKAWA, chiaki" Cc: gdb@sourceware.org, ysato@users.sourceforge.jp Subject: RE: h8300 sim: what is "eightbit" memory =?UTF-8?Q?=3F?= Date: Wed, 17 Aug 2016 18:35:00 -0000 Mime-Version: 1.0 X-IsSubscribed: yes X-SW-Source: 2016-08/txt/msg00039.txt.bz2 mike>> if eightbit is just an address mode, that's dirt simple to handle mike>> a (void *)0 will go to the same memory location regardless of the mike>> addr mode used by an insn. but it isn't what the sim is doing today :(. If I remember correctly, the arm simulator does various calculations and pipeline tracking. It's been a while, but it was doing this in the giant instruction switch statement. I've not read or looked at the H8 simulator does the H8 simulator sort of "count instruction/clock time" - based on memory accesses? The old 6502 had a very similar zero page feature (first 256 bytes) - aka: a zero page instructions. Accessing zero page using a zero page instruction required 3 clocks (aka: the first 256 bytes) Accessing absolute required 4 clocks, but you *CAN* access zero page in absolute mode if you choose This was useful when I wrote bit-bang uart simulation code (ie: Tight SW loop - to emulate a uart via GPIO pin) Thus - from a logical view the "memory is just memory" end of story. if this is not evident in the simulation code, this might have been a planned feature that never materialized or was never finished. this wiki page talks about it: https://en.wikipedia.org/wiki/Zero_page