Re: Apple2 disk controller questions

[lwalkerN0SpaM@interlog.com (Lawrence Walker)]

On 14 May 99 02:32:36 GMT, david@uow.edu.au (David Wilson) wrote:

>supertimer@aol.com (Supertimer) writes:
>>Wow!  Ok, next question: how does the Amiga fit 880k into a DS/DD 3.5" disk?
>
>From http://www.blizzard.u-net.com/expand/floppy.html:
>  
>     As well as the internal DF0: drive, the Amiga can have upto 3 external
>  drives (DF1-DF3). The Amiga normally uses Double Density drive (880k)
>  but can used specially made High Density drive (1.76Mb). 
>  
>     The Amiga differs from PC made drives in a number of ways: Paula custom
>  chip controls the floppy drives and uses non-standard 11 sectors/track
>  format (PCs use 9 sectors/track and is the reason why it is impossible
>  for them to read Amiga disks), uses a disk-detection system when disks are
>  inserted/removed  and a non-standard interface. Paula cannot cope with
>  high density drives at full speed and moved be slowed down to read/write high
>  density disks. This explains why Amiga HD drives are much more expensive.
>  
>     In place of a floppy drive it is possible to replace it with a 2nd
>  hard drive or even a Zip drive!
>  
>  Suppliers: Analogic Computers, Marpet Developments, EyeTech, First
>             Computer Centre, Power Computing and many more!
>
>So to add to my table:
>
>3.5"    300     0.167   250?    MFM?    50.00?  11*512  80/2    880     DSDD (B)
>3.5"    300     0.167   500?    MFM?    100.00? 22*512  80/2    1760    DSHD (C)
>
>(B)     Amiga DD
>(C)     Amiga HD (guessing about the 22 sectors)
>
>I am assuming that standard bit rates are used but this may not be the case
>(in order to fit the extra sectors)
>
>Then there is Microsoft's Distribution Format which fits more than 1440KB on
>a DS/HD 3.5" disk.

 This is a little further off-topic, but I have been trying to find an
answer for a while. 
 The Atari ST has several programs that allow you to increase the 720k
size by increasing the number of sectors up to 11,also speed and can't
remember but possibly sector size.. Many of the ST 'zine disks used
this method to jam their disks with programs, which couldn't be done
with 720k. Would it be possible to juggle the size and format disks
for the Amiga. Most stock PC 720k fdds can be used on an ST and they
can read/write Doze disks.

ciao		larry 
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