[Coco] Disk Drive formatting WAS:quick question
gene.heskett at verizon.net
Fri Dec 28 16:50:33 EST 2007
On Friday 28 December 2007, Steve Bjork wrote:
>On the loaders for my games, did I use an "every other one"
>interleaving. But I also change the size of the sectors to not only
>speed up the loading of the games but increase the storage on the floppy.
>If the sector jumps up form 256 to 1024 then you get an extra 512
>bytes per track. (or was it 512 bytes sectors? its been a long
>time.) What ever it was you got extra storage per track.
>Anyway, the interleave was 1,3,2,4,5. (or 1,3,5,7,9,2,4,6,8 for 512
>I'm starting think I used 512 byte sectors. As I said before, its
>been a long time.
>Oh yes, I do remember loading the whole track at once (into a screen
>buffer), tolled the controller to step to the next track. During the
>time it took the drive to step I used the time to moved the data to
>right place. There was no wasted time loading in the data and the
>floppy head just moved right long.
>Steve (6809er) Bjork
Now that is a neat trick, Steve. And it brings to mind the absolutely glacial
disk speeds that were obtained for a backup program I played with called bru.
Effective write speeds seemed to be the fastest when using an interleave of 8
when the disk was formatted. It took about 8:30 to write an 84 track 765K
disk. At the stock os9 interleave of 3, it was about 14 minutes so now you
know why no one, including me, ever ran it against a 130 meg hard drive more
than twice. Couple that with os9's lack of a file changed bit, and a backup
can only be described as painfull as its always a level 0.
The real surprise came at recovery time! From one disk formatted at an
interleave of 8, to read the full disk back and write it back to the hard
drive was an average of 29 minutes, during which the floppy motors ran
continuously. I did that once, for about 80 disks, plum wore out the heads
on a pair of Tandon 100-4's.
Treating the disk as a trackdisk like the amiga's did would have to be faster.
The question then is: Does os9/nitros9 have the ability to treat a disk as a
trackdisk, totally ignoring the index pulse and everything else that rbf.mn &
ioman normally handles. Its not something I have ever tried, but it would
certainly reduce the rotational latency's that seemed to be the cause of the
glacial speeds I was getting. It seems to me that would require a whole new
disk utility group of drivers to effect that since even the /d1@ still is
subject to the formatting of the disk.
>At 08:50 AM 12/28/2007, you wrote:
>>On Fri, 28 Dec 2007, Torsten Dittel wrote:
>> > I played around with that on the ATARI ST and didn't only change the
>> > sector interleave for one track but as well between the tracks (it
>> > wasn't necessary to start with the 1st sector right after the index hole
>> > so after stepping to the next track you wouldn't have to wait for the
>> > index hole passing by). I called this formatting "spiralization". Since
>> > the floppy disks were doublesided, another fixed sector # offset between
>> > side 0 and 1 made the disks reading even faster under normal TOS
>> > operation. However, I never tried to figure out the optimal "fast read"
>> > formatting for the CoCo (DECB or OS-9).
>> > Torsten
>>It would undoubtedly depend heavily on what step rate the drive was using.
>>If you optimized it for the 30 ms step rate that Disk Basic uses, you'd
>> negate the advantage of patching Disk Basic for a faster rate. Though I
>> suppose you could build a step rate parameter into this hypothetical
>>that would adjust the degree of "spiralization" depending on what
>>step rate you
>>wanted to optimize for.
>>Coco mailing list
>>Coco at maltedmedia.com
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