curtis_stevens at bannet.ptltd.com curtis_stevens at bannet.ptltd.com
Fri Sep 9 21:26:41 PDT 1994


	I just received a second E-Mail stating that BIOS in general does 
not support drives >528MB and that no consistent methods are being used to 
solve the problem.  You are also attempting to propagate the the rumor 
that LBA is required to access a drive with >1024 cylinders.  I am issuing 
this E-Mail as information on the Phoenix NuBIOS product.

1. Phoenix has already made available to its customers the INT 13 
Extensions designed by Microsoft and IBM.  These extensions have been 
tested by the Chicago group at Microsoft.

2. Phoenix supports the Enhanced Drive Parameter Table which was 
originally implemented by Compaq and documented in the Western Digital 
Implementation Guide.  Chicago, Windows NT and OS/2 are documented as 
gaining full access to drives with more than 1024 cylinders when the 
Enhanced Drive Parameter Table is present.  This table contains both the 
geometry reported by the drive (PHYSICAL GEOMETRY) and the geometry used 
by the BIOS (LOGICAL GEOMETRY).  This means that at least Phoenix, Compaq 
and IBM are shipping BIOS that works with large drives.  I have seen BIOS 
|from other vendors that appear to support this capability as well.

3. Phoenix does NOT require LBA to support drive with more than 1024 
cylinders (or greater than 528MB).  We perform CHS translation on drives 
using geometries and translation techniques which place the data in the 
same sectors that LBA would have used.  This means that the translation 
remains transparent to other software which may access the drive by 
bypassing the BIOS.

As far as Phoenix is concerned, INT 13 Fn's 0-19 will remain intact until 
the 8.4GB barrier is reached sometime next year.  The extensions are 
already being shipped and operate on drives regardless of their "LBA" 
capability.  The BIOS automatically translates if a drive does not support 
LBA.  I expect that at least 1 version of DOS which uses the Extensions 
will be in place by the time >8.4GB media becomes available to the public. 
 Current non-DOS OS software only uses INT 13 for booting the machine.  I 
know that at least one OS to be realeased shortly will install a master 
boot record which uses INT 13 extensions if they are present and I expect 
others to follow.

Curtis E. Stevens

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