Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!dimacs.rutgers.edu!aramis.rutgers.edu!paul.rutgers.edu!njin!uupsi!sunic!isgate!krafla!adamd From: adamd@rhi.hi.is (Adam David) Newsgroups: comp.os.minix Subject: Re: Larger / non-std fd formats (ST). Message-ID: <3157@krafla.rhi.hi.is> Date: 17 May 91 20:04:10 GMT References: <3115@krafla.rhi.hi.is> <3143@krafla.rhi.hi.is> <813@philica.ica.philips.nl> Organization: University of Iceland Lines: 42 In <813@philica.ica.philips.nl> adrie@philica.ica.philips.nl (Adrie Koolen) writes: >The most important problem however, is the reliability of the data storage. >In high density, you format 84 cylinders with 22 sectors of 512 bytes per track. >You cannot guarantee that every drive can read/write 84 cylinders and a drive >that cannot read past the 80th cylinder is not implicitly faulted. Furthermore, >the coating of the magnetic media need not extend to the 84th cylinder and when >it does, the coating on the last cylinder might not be as thick as on the first >80 certified cylinders. I agree that compatibility between different types of drives / controllers is a potential hazard well worth being aware of. Modern drives conform to a higher standard of design / manufacture in this respect. The old DD drives on the original ST could not guarantee beyond 82 sectors without filing away the headstop, but as far as I know most recent DD drives and all the newer HD drives step reliably out to 84 sectors. The drives on the first ST's might be expected to have a rotational speed somewhere between 295 and 305 rpm. Mine was somewhere between 300 and 301. Since I replaced it with HD drives I get better speed accuracy. Using an 84-track disk on an 82-track drive, a seek error occurs beyond the 82nd sector during read/write or format verify. (assuming that all tracks are formatted first before verifying the whole disk). Concerning floppy disks, the media on any disk worth buying extends beyond 85 tracks so there is no problem here except when buying disks from shoddy or ill-informed manufacturers. Only the 11 sector DD, 22 sector HD and 44 sector ED formats would have possible trouble sharing the disks between different drives using the same (or equivalent) floppy controller. This is because the sector gap is uncomfortably tight, particularly the 11 sector DD. Other computer systems than the ST use a wider range of controller types and this is where the biggest compatibility problem lies, but with modern equipment it is more likely that the hardware can cope, but the software doesn't know about it yet. An example was mentioned of failing to read old Commodore disks on an IBM PC. Both of these systems have known shortcomings in the disk controller circuitry, and this was before compatibility became a real issue. 10-sector DD disks shouldn't really run into any problems between different systems in use today. -- Adam David. (adamd@rhi.hi.is)