Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!ccu.umanitoba.ca!herald.usask.ca!alberta!brazeau.ucs.ualberta.ca!unixg.ubc.ca!ubc-cs!uw-beaver!zephyr.ens.tek.com!uunet!zaphod.mps.ohio-state.edu!ncar!noao!amethyst!mat From: mat@zeus.opt-sci.arizona.edu (Mat Watson) Newsgroups: comp.sys.next Subject: Re: Answer to External MO Disk Drive question. Message-ID: Date: 28 Jun 91 20:35:31 GMT References: <1991Jun28.145106.17420@agate.berkeley.edu> <1991Jun28.151037.19676@agate.berkeley.edu> Organization: University of Arizona Optical Sciences Center Lines: 49 In-reply-to: izumi@mindseye.berkeley.edu's message of 28 Jun 91 15:10:37 GMT izumi@mindseye.berkeley.edu (Izumi Ohzawa) > mat@zeus.opt-sci.arizona.edu (Mat Watson) writes: > > > >Important note: THE EXTERNAL CANON DRIVE IS UNABLE TO READ DISKS > >WRITTEN WITH THE INTERNAL CANON DRIVE FOUND ON THE CUBES. THIS > >INCLUDES SOFTWARE RELEASED BY NEXT ON MAGNETO-OPTICAL DISKS. The low > >level format for the internal disk is different than that used by the > >newer external SCSI drives even though the optical drive unit itself > >is essentially the same. > Does this incompatibility have to do with OD formatting > changes Canon made in Japanese NeXT OS 2.1J, rendering > 2.1J OD incompatible with 2.1 system? Someone from > Japan posted such a note in several postings back. > By any chance then, are OD's initialized on 2.1J compatible > with the Canon's external SCSI OD drive? > Is that why Canon changed OD filesystem for 2.1J? > I forgot to ask a few more things. > Are the media (optical disk cartridges) the same for this external > SCSI drive, and double sided OD's sold for NeXT? > Can they be made compatible if NeXT modifies their software? > I understand that magneto-optical's low-level format is > done at factory and not re-doable by user on OD drives. > If the difference is actually in low-level format, then > the media themselves may be incompatible. > Could someone clarify these points, and those in the previous posting? The media in both cases is the same, with the exception that the newer media is double sided. The formatting differences arise from hardware differences between disk controllers. I'm told that NeXT had to use a custom chip set to implement its internal optical drive system when it did. Now the disk controllers work of of the SCSI buss and use different (standard?) chip sets, hence the different low level format. As far as 2.1 vs. 2.1J goes, I would be quite surprised if that format difference occurs at this level, if in both cases you use the same type of drive (external SCSI for example). Just my own impression here; I'm really not an expert on this. More likely, the two differ in file format (contents). If this is the case, then formatting a disk under one OS version produces a disk usable by the other, and (in principle) one should be able to write software that converts between the different file formats. --Mat mat@zeus.opt-sci.arizona.edu