From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MmCXQ-0000Zw-HB for qemu-devel@nongnu.org; Fri, 11 Sep 2009 16:16:08 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MmCXL-0000T7-Ct for qemu-devel@nongnu.org; Fri, 11 Sep 2009 16:16:07 -0400 Received: from [199.232.76.173] (port=47821 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MmCXL-0000Sj-5I for qemu-devel@nongnu.org; Fri, 11 Sep 2009 16:16:03 -0400 Received: from mtaout03-winn.ispmail.ntl.com ([81.103.221.49]:18094) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MmCXJ-0005Ny-Ju for qemu-devel@nongnu.org; Fri, 11 Sep 2009 16:16:02 -0400 Received: from aamtaout04-winn.ispmail.ntl.com ([81.103.221.35]) by mtaout03-winn.ispmail.ntl.com (InterMail vM.7.08.04.00 201-2186-134-20080326) with ESMTP id <20090911201557.JMVS5579.mtaout03-winn.ispmail.ntl.com@aamtaout04-winn.ispmail.ntl.com> for ; Fri, 11 Sep 2009 21:15:57 +0100 Received: from miranda.arrow ([213.107.24.213]) by aamtaout04-winn.ispmail.ntl.com (InterMail vG.2.02.00.01 201-2161-120-102-20060912) with ESMTP id <20090911201557.ZMNQ22934.aamtaout04-winn.ispmail.ntl.com@miranda.arrow> for ; Fri, 11 Sep 2009 21:15:57 +0100 Received: from sdb by miranda.arrow with local (Exim 4.63) (envelope-from ) id 1MmCYW-0003RH-HR for qemu-devel@nongnu.org; Fri, 11 Sep 2009 21:17:16 +0100 Date: Fri, 11 Sep 2009 21:17:16 +0100 From: Stuart Brady Subject: Re: [Qemu-devel] Re: fdc: support NEC PC-9821 family Message-ID: <20090911201716.GA12245@miranda.arrow> References: <200909101629.AA00099@YOUR-BD18D6DD63.m1.interq.or.jp> <200909111136.AA00103@YOUR-BD18D6DD63.m1.interq.or.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <200909111136.AA00103@YOUR-BD18D6DD63.m1.interq.or.jp> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org On Fri, Sep 11, 2009 at 08:36:02PM +0900, 武田 俊也 wrote: > This is new patch. Nice work -- looks a lot closer! :) I've a few questions, though. I notice that the 82078 has 'PC AT', 'PS/2' and 'PS/2 Model 30' modes. QEMU doesn't seem to implement this, but I don't know common each of the different modes is/was. Also, I notice that in fdctrl_write_dor(), the DR0 bit (in PS/2 mode) is set if drives 0 or 2 are selected, which looks like a bug -- I would expect that it should only be set if drive 0 is selected. AFAIK, in most IBM PC 'clones' (but not quite all), the FDC can support four drives, but only up to one/two drives can be physically attached. It seems that MAX_FD affects emulation of the FDC itself, and doesn't just determine the number of drives that may be connected. Surely that can't be right? I.e. if MAX_FD == 2, any attempt to select drive 2 results in drive 0 being selected, which should not be the case... I'm not sure why QEMU limits certain machines to two drives... Maybe the reason is that software for systems where only two drives can be physically connected might react badly to seeing unexpected drives. Is this the case? TBH, I'm not sure whether I *really* need more than a single drive... :) Also, it seems to me that a floppy controller might have either one, two, three, four or no drives attached. (I assume that software can distinguish between a missing drive and a drive with no disk inserted.) In that case, it seems to me that QEMU cannot provide emulation of a system with no drives connected to its FDC. Cheers, -- Stuart Brady