Topic       : TOS - The Operating System
Author      : 
Version     : tos.hyp (December 19, 2008)
Subject     : Programmieren/Atari
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Index Size  : 93790
HCP-Version : 5
Compiled on : Atari
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View Ref-File14.8  XHDI - eXtended HardDisk Interface (Version 1.30)            TOS

The purpose of the XHDI (`eXtended HardDisk Interface') specification 
is to enhance the communication with drivers for block-oriented mass 
storage media. We started with the thought of creating a uniform 
interface for some additional driver features. One goal was to create 
a standard method for virtual memory systems to lock the eject button 
of Syquest hard disk drives (you don't want the user to remove the 
cartridge with the swap partition).

After further discussion, it was clear that the information available 
via the PUN_INFO structure just wasn't enough and that the missing 
information should be available with the help of this XHDI 
specification. Reasons:

   . The PUN_INFO structure only has room for 16 devices, but BIOS 
     (and some GEMDOS replacements) allow 32 devices

   . It is impossible to install more than one AHDI-compatible hard 
     disk driver in the system (there is only one PUN_INFO structure)

   . Atari's definition of device numbers only works for drives with 
     Logical Unit Number 0

For these reasons, the purpose of the XHDI specification is:

   . To provide more information about the installed devices

   . To support new driver features like Stop/Start or Lock/Unlock

The XHDI specification doesn't define new driver features - it should 
be easy to retrofit it into existing drivers.

See Also:
XHDI cookie   XHDI terminology   Partition types   Arbitration   XHDI 
functions   SCSI specification