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AST RESEARCH, INC.          TECHNICAL BULLETIN # 1251               7-14-95

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SCO UNIX 3.2V4.2 DOES NOT USE FULL CAPACITY OF 700MB TOSHIBA DRIVE IN 
ASCENTIA 910N


PROBLEM

When installing SCO UNIX 3.2 V4.2 on an Ascentia 910N system with a 700MB 
TOSHIBA drive, the size of the drive is rounded down to 500MB.


CAUSE

SCO Unix does not support Logical Block Addressing (LBA).  When drive 
parameters appear to exceed a cylinder count of 1024, or a head count of 16 at 
boot time, SCO assumes Enhanced IDE mode (EIDE) and restricts the drive to 
a maximum size of approximately 500MB.


SYSTEMS AFFECTED
AST PART NUMBER AND DESCRIPTION

All Ascentia 910N systems w/700MB Toshiba hard drives.


SOLUTION

The drive can be placed in an IDE-compatible mode which is supported by this 
version of SCO UNIX.  This is done by selecting "Fully Configuration 
Installation" during the install process and inputting the actual drive 
parameters from Toshiba as follows:

Cylinders = 1365
Heads = 16
Sectors/track = 63
 Landing Zone = 1365
Write Precomp = 0

These parameters will configure the drive to 700MB.  SCO supports up to 
2048 cylinders in an IDE-compatible mode, which means that the drive can be 
up to approximately 1GB.  In normal operation, when the system is booted, 
SCO will reference the masterboot block to get the actual drive parameters.