phil@sivax.UUCP (06/18/86)
AS I see it, the 800k format (or double-sided format, if you prefer), is set up for optimum head switching, ie the first x tracks are addressed by head 0 then the next x tracks are addressed by head 1 and so on throughout the disk. This seems ok on the surface, but wy not do it a little different for the following reasons: A disk has about 1600 sectors, a single sided disk has about 800 sectors. Why not just allocat sectors 0-800 (approx) to the first side, the 801-1600 to the second??? It would solve ALOT of current problems (some caused by user cheapness, but what the heck) 1) A disk could be initted as 800k, then a copy-protected disk could be copied to it in bit copy mode. A utility could be then written to tweak it back to 800k and voila, a useable 800k disk with the 400k copy protection intact!!! This would work since sectors 0-800 would still be accessed the same as on a 400k disk.... 2) Users who use Single-sided disks in double sided mode would find that their data is MUCH more intact from the initial copying to the 800k disk since the directory sectors would ALWAYS be on the first side. Even if the back of the disk went south one day, the initially loaded and most of the files stored on the back of the disk could be recovered. (I just had a disk sector 18, track 0, head 1 (back of disk) go bad. That is the 2nd block in the directory, so the disk was rendered unuseable). 3) current 400k disks could be turned into 800k disks very easily by a utility that could be written to format the back and tweak like in (1) above the disk to 800k. It would save alot of copying off of a disk, format, copying back to the disk files to cvt a disk to 800k. *****What does everybody think???***** *****Would this disk format be better or could it be added to the current *****driver as a format option?????? I think it would be great!!!!! Phil Hunt sivax!calma
briand@tekig4.UUCP (Brian Diehm) (06/19/86)
>Why not just allocat sectors 0-800 (approx) to the first side, the 801-1600 >to the second??? It would solve ALOT of current problems (some caused by >user cheapness, but what the heck) > >1) A disk could be initted as 800k, then a copy-protected disk could be copied >to it in bit copy mode. A utility could be then written to tweak it back to >800k and voila, a useable 800k disk with the 400k copy protection intact!!! Your suggestion, while maximizing compatibility between different formats, costs in terms of performance. It halves the amount of sequential data avail- able to the drive without seeking - i.e., while the same amount of data is under the heads, it is divided into two unrelated segments. The way it is cuts the number of seeks in half when reading long sequential files, provided they are not fragmented. IBM chose your suggested methodology for 5.25 drives; most disk designers were appalled at the choice. It was simply some questionable compatibility in exchange for a heavy performance penalty - and performance was one of the things that double-sided users were after. In my opinion, I've paid money for the extra capability of a different format, and I knew good and well that it WAS a different format. Pseudo-compatibility just raises more problems than if you simply tell people "It's a different format, so forget it. You can't use a double sided disk in a single sided drive." Trying to do that confuses everybody, and messes up performance for those who have paid for it. -Brian Diehm Tektronix, Inc. (The above is only MY opinion, the opinions of other people at this company may differ, and I don't think Tektronix has a company stand on this one way or another but I could be wrong. Why I remember once in 1954 I thought I was wrong, but. . .)
csanders@dopey..UUCP (Craig S. Anderson) (06/19/86)
In article <262@sivax.UUCP> phil@sivax.UUCP (Phil Hunt) writes: >AS I see it, the 800k format (or double-sided format, if you prefer), is set >up for optimum head switching, ie the first x tracks are addressed by head 0 >then the next x tracks are addressed by head 1 and so on throughout the disk. > >This seems ok on the surface, but wy not do it a little different for the >following reasons: > >Why not just allocat sectors 0-800 (approx) to the first side, the 801-1600 >to the second??? It would solve ALOT of current problems (some caused by >user cheapness, but what the heck) > > >*****What does everybody think???***** >*****Would this disk format be better or could it be added to the current >*****driver as a format option?????? > > >Phil Hunt >sivax!calma As far as I know, sectors are allocated by cylinder. Thus sector 0 is on the top and sector 1 is on the bottom of the first cylinder, etc. This is done to enhance speed, since one can eliminate alot of head seeks (which take a great deal of time) by allocating file sectors intelligently. Theoretically, with two sides one could eliminate up to half of head seeks or steps. It would be a nice option to be able to format disks your way, but this might confuse some users. I think all software houses should have an option in their copy protected software to move it to an HFS volume (either 800K or a hard disk). Craig Anderson
dennisg@sdcrdcf.UUCP (Dennis Griesser) (06/19/86)
In article <262@sivax.UUCP> phil@sivax.UUCP (Phil Hunt) writes: >AS I see it, the 800k format (or double-sided format, if you prefer), is set >up for optimum head switching, ie the first x tracks are addressed by head 0 >then the next x tracks are addressed by head 1 and so on throughout the disk. I heard that all the sectors on one track of side 0 are used and then all the sectors of the corresponding track on side 1. This type of allocation is called "cylinder". >Why not just allocat sectors 0-800 (approx) to the first side, the 801-1600 >to the second??? It would solve ALOT of current problems (some caused by >user cheapness, but what the heck) Allocating data sequentially across an entire side means that you have to move (step) the head twice as often to get to the data. And head stepping can take quite awhile. That's why Apple did it this way. It is one of the primary reasons why the 800K drives are so much faster. >1) A disk could be initted as 800k, then a copy-protected disk could be copied >to it in bit copy mode. A utility could be then written to tweak it back to >800k and voila, a useable 800k disk with the 400k copy protection intact!!! > >This would work since sectors 0-800 would still be accessed the same as on a >400k disk.... Cute, but there should be a better way to do it. Besides, copy protection is a bucket of slime anyway. >2) Users who use Single-sided disks in double sided mode would find that their >data is MUCH more intact from the initial copying to the 800k disk since the >directory sectors would ALWAYS be on the first side. Even if the back of the >disk went south one day, the initially loaded and most of the files stored on >the back of the disk could be recovered. (I just had a disk sector 18, track >0, head 1 (back of disk) go bad. That is the 2nd block in the directory, so >the disk was rendered unuseable). A poor argument. Lost data is lost data. You simply propose losing a different part of the disk. What if the front side went south one day? You lose it all anyway. >3) current 400k disks could be turned into 800k disks very easily by a >utility that could be written to format the back and tweak like in (1) above >the disk to 800k. It would save alot of copying off of a disk, format, copying >back to the disk files to cvt a disk to 800k. Nice. There should be a way to do this without scrapping the cylinder allocation. . . . . . . . Alternate proposal In the beginning of each disk are some bytes that tell what disk format is on the disk. I believe that these are called "signature bytes". One value means "400K" one meafs "000C"& T`ere are fdavgrs fgr EFS afd @FS$ afd sgee fgr Dasa&@gw abgut sgee sagfature bqtes t`at saq "088K(b}|(no|(allocated in cylinders". And let the file system do the right thing from there. That lets you get the perceived benefits of linear allocation and pay the necessary cost, or use cylinders and forgo the "800K is 400K plus some" similarity.
kearns@garfield.columbia.edu (Steve Kearns) (06/21/86)
compatability between 400k and 800k disks would be great, but your system will not do the trick because..... Files are not contiguous on the disk; one file might start in sector 8 and jump to sector 555. So Even if you have half the sectors you are not guaranteed of getting half the files. -steve