jeffn@pro-europa.cts.com (Jeff Noxon) (10/20/89)
Brian Willoughby asked if I had read/written 720k disks from experience, and my answer to this question is no. I now realize that it is in fact qute possible for the Apple 3.5 Drive to read/write an IBM format 720k disk. The PC Transporter does it. You CANNOT read or write a 720k IBM disk through the SmartPort, however. The reason for this is the smartport does not support the same modulation scheme the IBM disks use. Actually, I believe the SmartPort does support it but the IWM chip does not -- that is why the PC Transporter requires your 3.5" drives to be connected to it instead of the SmartPort: It can use it's own disk controller. Perhaps someone will one day create a peripheral card that does support the IBM modulation scheme so that we may transfer data without buying a PC Transporter. Or maybe someday Apple will let lowly GS users upgrade to a SWIM chip so all this can be done without a card. Also, someone mentioned something about Apple 3.5 drives speed control that didn't sound quite right. I can't find that post now. Anyway, the 3.5 operates at a variable recording speed depending on the track. The drive automatically adjusts this speed so it can fit the same amount of data on every track. Jeff |uucp: [ucsd, nosc] ..!crash!pro-houston!jeffn | "If I wanted your opinion, | |inet: jeffn@pro-houston.cts.com | I would have given it | |arpa: crash!pro-houston!jeffn@nosc.mil | to you!" |
dseah@wpi.wpi.edu (David I Seah) (10/24/89)
In article <8910200601.AA21133@trout.nosc.mil> jeffn@pro-europa.cts.com (Jeff Noxon) writes: >[Ponderings regarding 720K disk reads via Smartport deleted] >Also, someone mentioned something about Apple 3.5 drives speed control >that didn't sound quite right. I can't find that post now. Anyway, >the 3.5 operates at a variable recording speed depending on the track. >The drive automatically adjusts this speed so it can fit the same amount >of data on every track. I'm pretty sure that the drive adjusts its speed so it can fit VARIABLE amounts of data from track (or group of tracks) to track. By varying the drive speed, the track being read can be kept at a constant linear velocity with respect to the read/write head. With a fixed speed drive, angular velocity is constant. This doesn't take advantage of the physical track length differences. The outer tracks are longer (ala 2*pi*radius) than the inner tracks, and hence can hold more data. Since the data read/write is clocked, ya got to vary the drive speed to use it all. Another garbled followup from -- Dave Seah | O M N I D Y N E S Y S T E M S - M | Internet: dseah@wpi.wpi.edu | User Friendly Killing Machines | America Online: AFC DaveS "MY GOD! I HAVE POCKETS!!! I CAN'T BELIEVE IT! I HAVE POCKETS!!" - Tick