From: Ethan Dicks (erd_at_infinet.com)
Date: 2003-08-27 16:52:30
> Hi All, thansk for the information so far... certainly helps! > > >Model D9090 D9060 > >heads per drive 6 4 > >formatted storage > >capacity per unit 7,47Mb 4,98Mb > > >cylinders(tracks) 153 153 > >sectors/cylinder 128 192 > >sectors per track 32 32 > >blocks per sector 256 256 > > I'd seen this info, and hence my confusion.. the work "cylinders" in > two lines. It's as we were saying - "cylinders" refers to the number of discrete steps the head-positioner can make, regardless of the number of heads. "sectors/cylinder" tells you how many sectors are available without moving the heads (since in drive electronics of this era, the controller first moves the positioner, then, after some settling time, selects a head and waits for a particular sector to pass by the heads). I would like to point out that "blocks per sector" above should read "bytes per sector" > By "logical" I was refering to what the programmer would use when > they sent a U1 or U2 command. Commodore drive speak comes from a floppy mentality. All of the programs and documentation are oriented around single-sided disks. When addressing a 2040/4040/2031/1540/1541, it's fairly straightforward - "Track" means where the head is, and "sector" means where on the track the data is. Strictly speaking, even a 1541 floppy has cylinders - there's just one track per cylinder, and the number of sectors per track equals the number of sectors per cylinder (but it's variable depending on the track number, much the same with modern hard drives). It's been years since I did any low-level data work with my D9060 or D9090 (mostly, I've been trying to understand the firmware), but AFAIK, the number you want to use for "track" is going to be the cylinder number (i.e. - 0-153 for either drive), and "sector" is going to range between 1-128 or 1-192, depending on if it's a D9060 or a D9090. The suggests a limit of 65280 total sectors if you were re-writing the firmware to support larger drives (16.7 million bytes or 15.9 honest megabytes). This would be with an 8-head drive, using 256 tracks of it. I'm sorry if "cylinders" is confusing, but in this case, it _is_ the way you have to think of the drive to figure out where stuff goes. > Come to think of it... do these drives > support U1, U2 or do they need B-R and B-W??? AFAIK, yes. It's DOS 3.0, a direct descendent of the DOS used in the floppy drives. The main difference is being able to handle a BAM that grows and doesn't live on a particular, single cylinder (track). > I was thinking this era in Commodore's history... for example the > CBM 8250 etc rather than specific mechanisms. http://commodore.ca/manuals/commodore_1541_4040_8050_8250_comparison.htm -- Visit "The Seventh Continent" http://penguincentral.com/penguincentral.html Message was sent through the cbm-hackers mailing list
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