wdao@castor.usc.edu (Walter Dao) (06/22/89)
Lately I have been playing with the Disk drive. Now I have a question, I have done several testing and what I got was that one can stuff as much byte on track 80 as on track 0. Why ? Couldn't one write more data on track 0 (outer most) than on track 80 (innermost) ? . also is there another mean to access the disk drive ? the first method is to use amiga dos the second method is to use the .device (and all the DOIO stuff) the third way is to stuff the DMA with strategic values and wait . is there a fourth way ? (like a very CPU intensive not relying on the DMA etc ... ?) thanks ... 8-#
jms@tardis.Tymnet.COM (Joe Smith) (06/23/89)
In article <4167@merlin.usc.edu> wdao@castor.usc.edu (Walter Dao) writes: >Couldn't one write more data on track 0 (outer most) than on track 80 > (innermost) ? . As long as the drive uses a constant speed (RPM) and the disk controller uses a constant frequency (bits per second), the outer tracks will hold the same number of bytes as the inner tracks. That's the easiest way to design the hardware, even though it means that the bits are farther apart on the outer tracks and squeezed too close on the inner tracks. By increasing the data clock or decreasing the motor speed, one can put more bytes on the outer tracks. Apple does the latter on the Macintosh drives, using 8, 9, 10, 11, and 12 sectors per track, depending on which track it is reading. Which leads to a commonly asked question: Why can't the Amiga read Mac floppies? Answer: Because it wasn't designed to. Hacking with the existing hardware does not work; the only reliable way to do it is to use a different drive. Such as plugging an Apple compatible disk into the A-MAX box. -- Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com McDonnell Douglas FSCO | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-D21 | PDP-10 support: My car's license plate is "POPJ P," San Jose, CA 95161-9019 | narrator.device: "I didn't say that, my Amiga did!"
faulkner@jmullins.harvard.edu (Don Faulkner) (06/24/89)
buzz abbrevs: CAV Constant Angular Velocity Disk spins at constant RPM CLV Constant Linear Velocity (for constant data rate) Disk puts more data on outer tracks Disk spins faster on outer tracks -- Don Faulkner Building 1, Room 803 Harvard University, School of Public Health 665 Huntington Avenue Boston, MA 02115 ARPA: faulkner%jmullins@harvard.harvard.edu BITNET: faulkner@harvard Telephone: (617) 732-2297
?) Seaman) (06/27/89)
faulkner@jmullins.harvard.edu (Don Faulkner) writes:
< CLV Constant Linear Velocity
< (for constant data rate)
< Disk puts more data on outer tracks
< Disk spins faster on outer tracks
Don't you mean SLOWER on the outer tracks?
< Don Faulkner
--
Chris (Insert phrase here) Seaman | ___-/^\-___ bIyIn nI' je chep.
crs@cpsc6a.att.com <or> | //__--\O/--__\\ (Look it up
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The Home of the Killer Smiley | `\ /' Klingon Dictionary)jan@oscsunb.osc.edu (Jan's Student) (06/27/89)
In article <557@cpsc6b.cpsc6a.att.com> crs@cpsc6b.cpsc6a.att.com (Chris (Is it Friday yet?!?!?) Seaman) writes: >faulkner@jmullins.harvard.edu (Don Faulkner) writes: >< CLV Constant Linear Velocity >< (for constant data rate) >< Disk puts more data on outer tracks >< Disk spins faster on outer tracks > >Don't you mean SLOWER on the outer tracks? > No, in order to get the same amount of data in a larger track with a larger circumference (which is what the outer tracks are) the drive head must be spinning faster to cover the greater distance in the same amount of time. =============================================================================== John Michalos | Disclaimer: All of the above opinions are my Ohio Supercomputer Center | own and in no way reflect those of OSC jan@osc.edu | or Jan Labanowski. =============================================================================== -=- =============================================================================== John Michalos | Disclaimer: All of the above opinions are my Ohio Supercomputer Center | own and in no way reflect those of OSC jan@osc.edu | or Jan Labanowski.
) Seaman) (06/28/89)
jan@oscsunb.osc.edu (Jan's Student) writes: < crs@cpsc6b.cpsc6a.att.com (Chris (Is it Friday yet?!?!?) Seaman) writes: < >faulkner@jmullins.harvard.edu (Don Faulkner) writes: < >< CLV Constant Linear Velocity < >< (for constant data rate) < >< Disk puts more data on outer tracks < >< Disk spins faster on outer tracks < > < >Don't you mean SLOWER on the outer tracks? < > < No, in order to get the same amount of data in a larger track with a larger < circumference (which is what the outer tracks are) the drive head must be < spinning faster to cover the greater distance in the same amount of time. < < John Michalos You had better re-read the original posting - it was talking about CLV, which allows for MORE data on the outer tracks, and the disk does spin more slowly to achieve this. If the drive were to spin faster on the outer tracks, it would fit LESS data on them. BTW, to fit the same amount of data on a larger circumference as a smaller one, the rotation speed does not change, this is what the original poster was talking about when they referred to CAV (constant ANGULAR velocity). -- Chris (Insert phrase here) Seaman | ___-/^\-___ bIyIn nI' je chep. crs@cpsc6a.att.com <or> | //__--\O/--__\\ (Look it up ...!att!cpsc6a!crs | // \\ in your The Home of the Killer Smiley | `\ /' Klingon Dictionary)
ckp@grebyn.com (Checkpoint Technologies) (06/28/89)
In article <226@oscsuna.osc.edu> jan@oscsunb.UUCP (Jan's Student) writes: >In article <557@cpsc6b.cpsc6a.att.com> crs@cpsc6b.cpsc6a.att.com (Chris (Is it Friday yet?!?!?) Seaman) writes: >>faulkner@jmullins.harvard.edu (Don Faulkner) writes: >>< CLV Constant Linear Velocity >>< (for constant data rate) >>< Disk puts more data on outer tracks >>< Disk spins faster on outer tracks >> >>Don't you mean SLOWER on the outer tracks? >> >No, in order to get the same amount of data in a larger track with a larger >circumference (which is what the outer tracks are) the drive head must be >spinning faster to cover the greater distance in the same amount of time. > I've seen soooo many people get this confused... A disk has more linear space on the outer tracks than the inner track. Therefore, when the disk is spinning at a constant rate, the outer tracks are travelling at a greater linear velocity than the inner tracks. To get the same linear density on the outer tracks as the inner tracks, you either need to increase the data rate to match the outer track's greater linear velocity, or else *slow down* the angular velocity so that the outer track's linear velocity is the same as was the inner tracks' velocity at the higher angular speed. First comes the logo: C H E C K P O I N T T E C H N O L O G I E S +--------+ |\\ / / | Then, the disclaimer: All expressed opinions are FACT! | \ / o | Now for the witty part: I'm pink, therefore, I'm spam! +--------+ -- First comes the logo: C H E C K P O I N T T E C H N O L O G I E S +--------+ |\\ / / | Then, the disclaimer: All expressed opinions are FACT! | \ / o | Now for the witty part: I'm pink, therefore, I'm spam! +--------+
jbh@mibte.UUCP (James Harvey) (07/05/89)
In article <269@tardis.Tymnet.COM>, jms@tardis.Tymnet.COM (Joe Smith) writes: > In article <4167@merlin.usc.edu> wdao@castor.usc.edu (Walter Dao) writes: > >Couldn't one write more data on track 0 (outer most) than on track 80 > > (innermost) ? . > > As long as the drive uses a constant speed (RPM) and the disk controller uses > a constant frequency (bits per second), the outer tracks will hold the same > number of bytes as the inner tracks. That's the easiest way to design the > hardware, even though it means that the bits are farther apart on the outer > tracks and squeezed too close on the inner tracks. > > By increasing the data clock or decreasing the motor speed, one can put more > bytes on the outer tracks. Apple does the latter on the Macintosh drives, > using 8, 9, 10, 11, and 12 sectors per track, depending on which track it > is reading. > > Which leads to a commonly asked question: Why can't the Amiga read Mac > floppies? Answer: Because it wasn't designed to. Hacking with the existing > hardware does not work; the only reliable way to do it is to use a different > drive. Such as plugging an Apple compatible disk into the A-MAX box. > > -- > Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com > McDonnell Douglas FSCO | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms > PO Box 49019, MS-D21 | PDP-10 support: My car's license plate is "POPJ P," > San Jose, CA 95161-9019 | narrator.device: "I didn't say that, my Amiga did!" The latest and greatest Copy II PC option board for the International BM computers will read (and convert to IBM) Mac disks. If they can do it, why can't Amiga? -- Jim Harvey | "Ask not for whom the bell Michigan Bell Telephone | tolls and you will only pay 29777 Telegraph | Station-to-Station rates." Southfield, Mich. 48034 | ulysses!gamma!mibte!jbh
jms@tardis.Tymnet.COM (Joe Smith) (07/07/89)
In article <2832@mibte.UUCP> jbh@mibte.UUCP (James Harvey) writes: >The latest and greatest Copy II PC option board for the >International BM computers will read (and convert to IBM) Mac >disks. If they can do it, why can't Amiga? Because the Copy II PC option board has special hardware designed just for reading Mac disks. If you plug special hardware into the Amiga, it could read them too. -- Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com McDonnell Douglas FSCO | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-D21 | PDP-10 support: My car's license plate is "POPJ P," San Jose, CA 95161-9019 | narrator.device: "I didn't say that, my Amiga did!"