NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/sys/amiga/hardware-part1/5430

Internet Message Format | 1996-08-05 | 1.7 KB

Path: rpool13.rus.uni-stuttgart.de!etk11485
From: Joerg Deutschle <[e-mail]>
Newsgroups: comp.sys.amiga.hardware
Subject: 150RPM-300RPM HD-Floppys
Date: Fri, 16 Feb 1996 09:51:25 +0100
Organization: Comp.Center (RUS), U of Stuttgart, FRG
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Hi to all out there,

in the description of the PAULA-registers you  can find a BIT  that is
called "FAST" which apperently switches the floppy-controller from
4 micro seconds/bit to 2 micro sec/bit. The 4 us/bit would be for the
GCR-mode (look in some manual  about good old C64  floppystation
1541) whereas the 2 us/bit are  used  for the MFM-mode. This indicates
that PAULA is capable of  250,000 Bits/s or 500,000 Bits/s data output.
With 5 rounds per second  (=300rpm)  you  get  50,000 Bits/track or
100,000 Bits/track, what would be 6,250 Bytes/track or  12,500
Bytes/track. Since the Amiga floppy-format is using MFM one could get
12,500 Bytes on one  track. Of course you have to take into
consideration that the MFM codeing, the sector and data-block headers and
syncs take their price, in effect, you can strore  only half  that much
on one track. With the standard Amiga floppy-format  you have
11 sectors with 512 bytes per track  (=5,5 Kbytes).  On HD-disks you
have  twice that much,  i.e. 11kbytes. In order to store that much data
on one  track  at  300rpm you  need twice the  data-rate from the
floppy-controller. Makes around  1,000,000 bits/s  !!!

If someone does not agree, please feel  free to  argue.
Perhaps someone from AT can make a comment on this!!

Godbye,  Joerg!