From: usenet@tim-mann.org   
      
   On Wed, 12 Apr 2006 00:54:22 +0200, Knut Roll-Lund  wrote:   
   > Roberto Bazzano wrote:   
   > ...   
   > > It should be model I compatible, but it's single density and the directory   
   > > id marks are not readable by the standard pc floppy controller.   
   > > This is because I thought to catweasel.   
   >   
   > I have several PC's that can read these disks with the floppy controller   
   > on the motherboard. To my surprise one pentium 200MHz I have can even   
   > format model I disks. I use David Keil's emulator. I never felt the need   
   > for a catweasel. I think the biggest problem people have is that they   
   > use WinXP and it won't allow direct access to the floppy controller.   
      
   You were probably reading disks written by newer Model I DOS's that use   
   (or can use) 0xF8 data address marks on the directory track instead of   
   the 0xFA marks of the original TRSDOS 2.x and NEWDOS 2.1.  Later DOSes   
   switched to F8 for Model III/4 compatibility, because Model III/4 can't   
   write sectors with FA DAMs, and can read them but can't tell the FA DAM   
   apart from the FB DAM used on non-directory tracks.   
      
   My experience (admittedly on a small sample of machines) is that PC FDCs   
   can't read sectors with FA DAMs at all -- they are not recognized as   
   valid sectors.  It's certainly possible that some PC FDC's can read   
   them, but it seems unlikely.   
      
   --   
   Tim Mann  usenet@tim-mann.org  http://tim-mann.org/   
      
   --- SoupGate-Win32 v1.05   
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