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AST RESEARCH, INC.        TECHNICAL BULLETIN # 1095                  3-9-95

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				 INCOMPATIBILITY ON LARGE IDE DRIVES


PROBLEM

There is a potential for incompatibility on IDE drives larger than 528M, when 
switching drives from one vendor's machine to another. 

The underlying reason for this incompatibility is due to a lack of standards 
when developing a BIOS.  Various BIOS writers at different companies have 
implemented the necessary translation of the drive geometry for these larger 
drives.

CAUSE

The main trigger for this incompatibility is if the large drive being used 
does not specify its drive geometry to use the maximum of 63 sectors per track.  
Most drive vendors have made their large capacity drives with the 63 sector 
per track maximum.  However, there are a few models such as the Quantum LPS 
and Quantum Lightning hard drives which do not abide by this rule.

SYSTEMS AFFECTED
AST PART NUMBER AND DESCRIPTION

All AST systems using IDE drives larger than 528 MB.

SOLUTION

Before moving a large IDE drive from one system to another, go through the 
following checklist:

1. Do both the source and destination systems use the same BIOS vendor?  
   If the answer is yes, there should not be a problem transferring any drive 
   from one system to the other.

2. If the BIOS vendor is not the same on both the source and destination 
   systems, check the drive geometry.  If the sectors per track are 63, 
   transfering the drive should not cause a problem. Go into System Setup and 
   look under "hard drive" to find out how many sectors per track your hard 
   drive has.

3. If the BIOS vendor is not the same and, if the sectors per track of the 
   drive in question are not 63, then use the user-defined drive option to 
   configure the destination system with the translated drive geometry 
   identified by the source system.

Note: Back up the data before moving the drive.  If the destination and source 
systems do not use the same BIOS, the user-defined option should be used.  
In that case, the drive may not map out to the full capacity unless it is 
backed up, repartitioned, reformatted under the new user defined option.  
Simply to plug in the drive and set up user defined option will result in 
loss of some capacity (sometimes as large as 50MB.-E.M>).