Re: Apple II Disk Drive Question

["Jack Tseng" <tseng4@hotmail.com>]

Bryan,

I know you... Were you NTID/RIT student before?


"Bryan Parkoff" <none@nospam.net> wrote in message 
news:2iLQf.313$tN3.261@newssvr27.news.prodigy.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
>
>