macq@miguel.llnl.gov (Don MacQueen) (09/21/90)
1) Many articles have warned against plugging in/unpluggin ADB cables while the Mac is on. What about the modem cable? I sometimes want to unplug my modem cable from its line to a local mainframe and plug it back in to the serial port of a PC (with null modem) for file transfer. Is there a danger of hardware damage? 2) Many articles discuss interleave re hard disk read/write speed (eg MacPlus 3:1, SE 2:1, others 1:1). None that I've read say when/where/what establishes the interleave. Is it done at disk format time (with disks sold preformatted I've never needed to format a disk)? by the device driver software? In short, how do I find out if I have the right interleave, and if not, change it? Thanks in advance. Don MacQueen macq@miguel.llnl.gov
umcarls9@ccu.umanitoba.ca (Charles Carlson) (09/25/90)
In article <1990Sep20.123824@miguel.llnl.gov> macq@miguel.llnl.gov (Don MacQueen) writes: > >1) Many articles have warned against plugging in/unpluggin ADB cables >while the Mac is on. What about the modem cable? I sometimes want to >unplug my modem cable from its line to a local mainframe and plug it >back in to the serial port of a PC (with null modem) for file transfer. >Is there a danger of hardware damage? Been plugging/unplugging serial cables to/from PCs and Macs for years. Never had a single problem with it. Only time I ever lost a serial port was when lightening struck the phone line, hit the modem and into the serial port. Luckily it stopped there. Never heard a modem scream so in my life. The modem was toast, but the serial port was fixed for $1.89. >2) Many articles discuss interleave re hard disk read/write speed (eg >MacPlus 3:1, SE 2:1, others 1:1). None that I've read say >when/where/what establishes the interleave. Is it done at disk format >time (with disks sold preformatted I've never needed to format a disk)? >by the device driver software? In short, how do I find out if I have >the right interleave, and if not, change it? Interleave is set during the low level initialization. There are typically two types of formatting. Low level which is done first, then the high level which is specific to the operating system. To look at/change the interleave you need a low level formatting program. Your hard drive more than likely came with one that does this, but it might not let you set or even see the interleave. A good utility for that is Silver Lining. Does anyone know if Norton Utilities allows you to look at/change the interleave without reformatting? Charles
emmayche@dhw68k.cts.com (Mark Hartman) (09/30/90)
In article <1990Sep25.042714.25505@ccu.umanitoba.ca>, umcarls9@ccu.umanitoba.ca (Charles Carlson) writes: >Does anyone know if Norton Utilities allows you to look at/change the >interleave without reformatting? Generally speaking, this is not possible to do. Interleaving describes the number of sectors which are read out of the number that pass beneath the r/w heads. So, for example, an interleave of 1:3 takes three turns of the disk to read the entire track. Needless to say, the sectors are positioned in a like manner; i.e., sector "1" and sector "2" have two other physical sectors between them. While I suppose you *could* change the interleave factor, the amount of data shuffling you'd have to do to make it work properly really wouldn't be worth the hassle. -- ------------ Mark Hartman uucp: ...{spsd,zardoz,felix}!dhw68k!emmayche Internet:emmayche@dhw68k.cts.com CompuServe: >internet:emmayche@dhw68k.cts.com Applelink: N1083
umcarls9@ccu.umanitoba.ca (Charles Carlson) (10/05/90)
In article <1990Sep30.060736.28468@dhw68k.cts.com> emmayche@dhw68k.cts.com (Mark Hartman) writes: >In article <1990Sep25.042714.25505@ccu.umanitoba.ca>, >umcarls9@ccu.umanitoba.ca (Charles Carlson) writes: > >>Does anyone know if Norton Utilities allows you to look at/change the >>interleave without reformatting? > >Generally speaking, this is not possible to do. Interleaving describes >the number of sectors which are read out of the number that pass beneath >the r/w heads. So, for example, an interleave of 1:3 takes three turns >of the disk to read the entire track. Needless to say, the sectors are >positioned in a like manner; i.e., sector "1" and sector "2" have two >other physical sectors between them. > >While I suppose you *could* change the interleave factor, the amount of >data shuffling you'd have to do to make it work properly really wouldn't >be worth the hassle. Of course its possible to do! There are countless programs available for the PC to do it! What data shuffling are you talking about? All you simply have to do is: 1) read the track into memory 2) reformat track to desired interleave 3) write data back to disk. Which would be quicker and easier? That or: 1) backing up drive <which you should do anyways before something like this> 2) reformat old drive 3) restore all the data. Charles
rlwald@phoenix.Princeton.EDU (Robert L. Wald) (10/05/90)
In article <1990Sep30.060736.28468@dhw68k.cts.com> emmayche@dhw68k.cts.com (Mark Hartman) writes: >In article <1990Sep25.042714.25505@ccu.umanitoba.ca>, >umcarls9@ccu.umanitoba.ca (Charles Carlson) writes: > >>Does anyone know if Norton Utilities allows you to look at/change the >>interleave without reformatting? > >Generally speaking, this is not possible to do. Actually, you can do this on a PC. There is a good package called Spinrite II which does this. It reformats each track as it goes, preserving the data and correcting any looming errors way before the error correcting circuitry will break down over them. But as far as I know, its not available for the Mac. -Rob "Its a good thing frogs can hop, or I'd be Gone With the Schwinn!" rlwald@phoenix.princeton.edu
kaufman@Neon.Stanford.EDU (Marc T. Kaufman) (10/05/90)
In article <1990Oct4.192735.8812@ccu.umanitoba.ca> umcarls9@ccu.umanitoba.ca (Charles Carlson) writes: >In article <1990Sep30.060736.28468@dhw68k.cts.com> emmayche@dhw68k.cts.com (Mark Hartman) writes: ->In article <1990Sep25.042714.25505@ccu.umanitoba.ca>, ->umcarls9@ccu.umanitoba.ca (Charles Carlson) writes: -->Does anyone know if Norton Utilities allows you to look at/change the -->interleave without reformatting? ->Generally speaking, this is not possible to do... >Of course its possible to do! There are countless programs available for the >PC to do it! >What data shuffling are you talking about? All you simply have to do is: >1) read the track into memory >2) reformat track to desired interleave >3) write data back to disk. All very fine with an ST506 interface, but not generally doable with a SCSI interface. With most SCSI drives, you aren't even sure which sectors make up a track. Marc Kaufman (kaufman@Neon.stanford.edu)
peter@hari.Viewlogic.COM (Peter Colby) (10/09/90)
In article <1990Oct4.192735.8812@ccu.umanitoba.ca>, umcarls9@ccu.umanitoba.ca (Charles Carlson) writes: |> >While I suppose you *could* change the interleave factor, the amount of |> >data shuffling you'd have to do to make it work properly really wouldn't |> >be worth the hassle. |> |> Of course its possible to do! There are countless programs available for the |> PC to do it! |> What data shuffling are you talking about? All you simply have to do is: |> 1) read the track into memory |> 2) reformat track to desired interleave |> 3) write data back to disk. Sigh! The PC ain`t SCSI. The PC runs generally standard ST506 interface drives which I suppose allow you to format on a track by track basis. SCSI hides all the low level access to the disk in the SCSI controller tied to the disk. For every SCSI drive (or SCSI controlled ST506 drive) I have ever seen or heard of, formatting is an all or nothing process. In fact, most of the (no longer very) new embeded SCSI drives don't even allow you to cheange the interleave at all. They do all sorts of fancy stuff like force 1:1 interleave or special zone recording or whatever and hide it all in the board stuck to the drive. You don't even need to know your drive's geometry any more!! Peter C -- (O)(O)(O)(O)(O)(O)(O)(O)(O) (O)(O)(O)(O)(O)(O)(O)(O)(O) (O) !the doctor is out! (O) (0) peter@viewlogic.com (0) (O)(O)(O)(O)(O)(O)(O)(O)(O) (O)(O)(O)(O)(O)(O)(O)(O)(O)