From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1O26iK-00034J-Kv for qemu-devel@nongnu.org; Wed, 14 Apr 2010 13:49:24 -0400 Received: from [140.186.70.92] (port=57293 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O26iF-0002yb-Hx for qemu-devel@nongnu.org; Wed, 14 Apr 2010 13:49:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1O26iE-0000ue-L4 for qemu-devel@nongnu.org; Wed, 14 Apr 2010 13:49:19 -0400 Received: from chello212186124096.11.vie.surfer.at ([212.186.124.96]:44882 helo=wiesinger.com) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1O26iE-0000uF-7f for qemu-devel@nongnu.org; Wed, 14 Apr 2010 13:49:18 -0400 Date: Wed, 14 Apr 2010 19:48:44 +0200 (CEST) From: Gerhard Wiesinger Subject: Re: [Qemu-devel] Problem with DOS application and 286 DOS Extender application In-Reply-To: <20100413232056.GA21321@shareable.org> Message-ID: References: <20100413232056.GA21321@shareable.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jamie Lokier Cc: qemu-devel@nongnu.org, Roy Tam On Wed, 14 Apr 2010, Jamie Lokier wrote: > Gerhard Wiesinger wrote: >> It is a non public, proprietary application which uses the Ergo Computing >> 286 DOS Extender. I guess some other application which use the same DOS >> extender have the same problem. So best thing is to find another >> application which uses the Ergo Computing 286 DOS Extender, too. > > The 286 was obsolete 20 years ago, although code depending on it > persisted for some years after. > > I'm fairly sure the number of people using (or trying to use) Qemu > with 286-specific code is very small indeed, so unfortunately for a > 286 problem, you will need to help reproduce it as much as you can for > it to be fixed. > > Note that Qemu doesn't emulate segments properly even for 32-bit x86 > code, and 16-bit (286) code depends on that all the more. That may be > the problem. > > Or it may be the "reset using keyboard controller and BIOS" method > used to switch from protected mode to real mode on a 286 is not > implemented properly, or is not supported by the BIOS properly. > > Or it may simply be a bug in 16-bit task segment switching or > something like that, which is quite complex and so rarely used that it > might never have been properly tested. > > Did you try running the application under Bochs, which has a more > accurate emulation of very old x86 CPUs? Yes, Bochs is very slow but works well. Any plans to improve the handling of the above issues? BTW: 386 DOS Extender applications seem to work ok even on QEMU. Ciao, Gerhard