Re: Apple II Disk Drive Question

["Bryan Parkoff" <none@nospam.net>]

"David Empson" <dempson@actrix.gen.nz> wrote in message 
1hc37c1.zm35pr1p8py2mN%dempson@actrix.gen.nz">news:1hc37c1.zm35pr1p8py2mN%dempson@actrix.gen.nz...
> Jack Tseng <tseng4@hotmail.com> wrote:
>
>> How many sectors and track are max in Apple II Disk Drive?
>
> I assume you are talking about the original 5.25" drive (Disk ][) and
> later revised models (UniDisk 5.25, Disk //c and Apple 5.25 Drive), not
> the 3.5" drives.
>
> The original format, as used by DOS 3.2.1 and earlier, was 256 bytes per
> sector, 13 sectors per track, 35 tracks per disk (single sided), for a
> total capacity of 116480 bytes.
>
> DOS 3.3 and Apple II Pascal introduced the 16-sector format (also used
> by ProDOS), which involved some improvements in the logic state
> sequencer on the disk controller card.  The increase in sectors per
> track brought the total capacity to 143360 bytes.
>
> Most Apple 5.25" drives are capable of a few more tracks, so a
> nonstandard disk could be created on a specific drive with 36 to 40
> tracks, but it might not be readable on all drives.  One of my drives
> managed 39 tracks but I haven't done a wide survey.
>
> Some third party drives could manage 40 tracks consistently.
>
>> Is it MFM or GCR
>
> GCR.  Address fields in both formats are written using 4-and-4 encoding
> (effectively FM, with interleaved clock and data bits).
>
> On 13-sector disks, data fields are written using 5-and-3 encoding with
> a 32-byte lookup table of valid disk bytes.  Each byte must have bit 7
> set and no adjacent zero bits.
>
> On 16-sector disks, data fields are written using 6-and-2 encoding with
> a 64-byte lookup table of valid disk bytes.  The rules are relaxed
> somewhat to allow a single pair of adjacent zero bits in the byte.
>
>> ? How fast is it? Max bps?
>
> Rotation speed is about 300 rpm.  Data rate is nominally 250 kbps (4
> microseconds per bit), derived from the Apple II CPU clock which runs at
> about 1.023 MHz, with one bit every 4 clock cycles, so about 255.75
> kbps.
>
> -- 
> David Empson
> dempson@actrix.gen.nz

David,

    I have a question.  If RPM is to be between 280 and 310.  Can you please 
tell how many KBps per second will be.  For example -- 300 RPM is 250KBps. 
280 RPM may be 220KBps.  310 RPM may be 280KBps.  Please list KBps each RPM 
like 280, 281, 282, and so forth until 310.  I am curious.

Bryan Parkoff