Message-Id: Date: Wed, 10 Dec 1997 19:29:09 +0000 From: Matthias Paul To: opendos AT delorie DOT com, paul-ma AT reze-1 DOT rz DOT rwth-aachen DOT de Subject: Re: Questions About DRIVPARM and TaskMgr Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Precedence: bulk On 97/12/10 Ben Jemmett replied: >>I recently installed a 3 1/2 disk drive on it. 720K disks work fine, but I get >>a "sector not found" error or "general error" when trying to use 1.44 MB >>disks. >Old, old, old 8088 - XT or previous, I assume. XTs and previous models >can't handle drives above 720K - the data seperator on the FDD controller >can't handle the data rates from 1.44 and 1.2 Mb drives - [...] This is correct, if speaking of the original XT-FDC controller. But many XTs today use FDCs on Multi-IO cards which usually support up to 2 drives á 1.44MB (some even support 4 drives á 1,44MB). They also have a ROM/EPROM which replaces the ROM-BIOS floppy code, so that these XTs are fully capable of 1,4MB drives. >Don't know about the switch, but the drive is not handled by the BIOS, so a >BIOS patch won't make your system compatible with high density drives. Not alone. To support 1,4MB drives (on any machine), it needs - a correctly jumpered 1,4MB drive (I assume this as given) - a FDC capable of the high density data rates (in my former reply I also assumed this as a given requirement) - a software driver, which usually resides inside of the ROM-BIOS, or in the case of AddOn FDCs, inside of an external ROM/EPROM. I refer to these ROM-based drivers in Digitial Research s terminology as ROS (ROM Operating System). (A software only driver like 2M s 2M-XBIOS is also possible without the need of a special ROM. It is just loaded by IBMBIO.COM) The (Real Mode) DOS kernel consists of two parts, the DOS portion of the "BIOS" (inside of IBMBIO.COM, that s why I usually call the ROM-based BIOS "ROS", not BIOS) and the "BDOS" (inside of IBMDOS.COM). In short words, the high level (and portable) DOS functions (in BDOS) are based on more-hardware-dependent drivers in the BIOS, which themselfs refer to the very-hardware-dependent ROS (which can be overlayed by an installable driver). Well, the terminology differs between authors, some call ROS+BIOS the BIOS... (which is also true). Anyway, given the proper hardware, it is possible to support 1,4MB floppies in PCs and XTs by a ROS update, or a software driver. Of course, the later solution cannot be used to boot from 1,4MB floppies, whereas this is obviously no problem for a ROS-based driver. Matthias ------------------------------------------------------------ Matthias Paul eMail: Web: http://www.rhrz.uni-bonn.de/~uzs180/mpdokeng.html