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AST RESEARCH, INC.         TECHNICAL BULLETIN # 1137                4-12-95

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				ASCENTIA 9XXN 810 MB HARD DISK DRIVE


This is an informational bulletin.

The 810 Megabyte hard disk drive for the Ascentia 9XXN system has demonstrated 
full compatibility with MS-DOS 6.XX, Windows 3.1X and Workgroups, and 
OS/2 2.XX/3.XX operating systems.  The drives additionally support SCO 
Unix/Open Desktop (ODT) with the exception of two areas:

1. While performing an infinite-loop outbound large file (>1MB) transfer using 
FTP, the Unix session which controls the transfer may freeze after a period of 
approximately 2 hours.  The system may still be shut down correctly, however, 
if a file is in the FTP queue for transmission, the data may be lost if the 
file was unsaved immediately prior to entering the queue.

The cause for this problem is in Unix itself, as it does not support drive 
geometries which have greater than 1024 cylinders.  Even if the drive is 
partitioned for 528MB (Unix maximum) the problem may still occur due to the 
translations for CHS embedded in the drive controller code.

2. When a user has configured the hard drive for both a Unix and an MS-DOS 
partition, the FTP activities under Unix may cause some clusters in the DOS 
partition to be erroneously marked as bad, when the user changes from the 
Unix partition to the DOS partition.  

The cause for this particular problem is that Unix uses some areas of CMOS 
for in-session configuration storage, and does not remove or reset the bits 
that were changed, causing DOS to perceive bad clusters.  
The workaround for this situation is to use CHKDISK.EXE with the /F switch, 
or SCANDISK (whichever is appropriate for the version of DOS being used) 
during the DOS session to restore clusters marked as bad in error, or to mark 
genuinely bad clusters.


SYSTEMS AFFECTED
AST PART NUMBER AND DESCRIPTION

All Ascentia 9XXN systems with 810 MB hard disk drives installed or with the 
option for 810 MB hard disk drives.