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Title:    3.2GB Limitation in Phoenix 4.03 and 4.04 BIOSes
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Filename: OVER3GB.TXT
WWW URL:  http://www.firmware.com/support/bios/over3gb.htm
FTP URL:  ftp://ftp.firmware.com/text/over3gb.txt
Author:   Terry Slade, Micro Firmware Technical Support
Revision: 02/24/98
Summary:  Some explanation of the 3.2GB hard drive size limitation
          in some Phoenix 4.03 and 4.04 BIOSes.
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Many Phoenix 4.03 and 4.04 BIOSes are limited to 3.2GB hard drives due
to a bug in the drive size calculation routines. This problem is in
the base code but may have been fixed by the OEM in any particular
BIOS version. This problem does not exist in any Micro Firmware BIOS
upgrades, as we identified and fixed it in our 4.03 code several 
years ago. This problem does not exist in any Phoenix 4.05 BIOSes.

The symptom is that the system will lock up in CMOS setup when
autotyping (or manually entering values for) drives of certain sizes.

Assuming 16 heads and 63 sectors, the cylinder field will accept
values up to 6349, which would be a 3277MB drive. With different
values for heads and/or sectors, the limit is still with the same
capacity.

Cylinder values from 6350 to 8322 (assuming 16 heads, 63 sectors)
will cause lockup in CMOS (may unfreeze in a minute or so).
The size range here is 3277MB to 4295MB.

Cylinder values from 8323 to 14671 will work, but the size displayed
in CMOS setup will be wrong. The size will be shown as 4295MB less
than the correct size. The size range here is 4295MB to 7572MB.
Although CMOS setup will not display the size correctly, this should
not cause any problems with the operation of the drive. FDISK will see
the entire capacity. Note that drives in this size range (using 16
heads) are over the limit of the 4.2GB limitation in DOS/WIN95. This
can be worked around by using 15 heads and multiplying cylinders by
16/15 (see OVER4GB.TXT http://www.firmware.com/support/bios/over4gb.htm ).
Drives in this range that have factory CHS values with 15 heads, such
as the Quantum Fireball ST64A, should work fine (that is, they need no
BIOS correction for the 4.2GB DOS bug, but will still not show the
correct capacity value in CMOS setup).

#
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Micro Firmware Technical Support
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Voice  405-321-8333           email  support@firmware.com
Fax    405-321-8342           WWW    http://www.firmware.com
BBS    405-573-5538           FTP    ftp://ftp.firmware.com
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