    Abit AX5/PX5 jumperless motherboard BIOS Ver 'GP' 11/13/1998
    with patch J.3 for AMD K6 model 7, K6-2, K6-III, and K6-2+/III+ support,
    and for IDE HDDs up to 128GB (32GB bugfix).
    10/20/2026
    by Jan Steunebrink

The latest, and probably final, BIOS upgrade from Abit for the AX5 and PX5 is
version 'GP' (PX5_GP.BIN).
This BIOS does not support the (mobile) K6-2+/III+ CPUs.
Also the original K6 model 7 (2.2v), K6-2 and K6-III are not supported.
The CPU SOFT MENU defaults to 2.90V Vcore for all K6 CPUs and this is way too
high for the K6 model 7/K6-2(+)/-III(+)!

To overcome these problems, I have patched the PX5_GP BIOS to include proper
recognition and handling of the K6, K6-2, K6-III, and K6-2+/III+.
I've made the following changes:
- Added detection of the K6-2+, and K6-III+ CPUs
- Expanded the K6 Write Allocation feature to work also on all K6-2/III CPUs
  with the CXT core and enabled this feature for the K6-2+ and K6-III+ as well
- Expanded the CPU Type display routine for correct display of the AMD-
  K6(tm)-III, K6(tm)-2+, and K6(tm)-III+ strings
- Added 6.0x83 (500MHz) and 6.0x75 (450MHz) support for the K6-2CXT, K6-III,
  K6-2+ and K6-III+.
- Changed the BIOS's Vcore control so that 2.4v, 2.2v, and 2.1v Vcore selections
  are now available in the CPU SOFT MENU. These new selections replace the old
  2.7v, 2.5v, and 3.2v selections which were of little value.
  The 2.8v and 2.9v Vcore selections are not changed and are still available,
  so are the 3.30v/3.38v/3.52V selections for Single Voltage CPUs.
- Changed the CPU SOFT MENU defaults to set the correct 2.4V/2.2V/2.1V Vcore
  voltage for each AMD K6 model 7, K6-2, K6-III, and K6-2+/III+ CPU
- Added x4, x4.5, x5, and x5.5 multiplier selections for applicable CPU models
  to the CPU SOFT menu.
- Added x6.0 multiplier support for the K6-2CXT/K6-2+/III(+), in CPU SOFT menu.
- Removed the Speed Error Hold function to allow stable CPU operation at
  speeds above 333MHz.
- Changed the WinChip 2A multiplier selections to show x2.5/x3.3/x3/x3.5
- Changed the Cx686(L) multipliers from a fixed x2 to a selectable x2/x3.

In addition I have made a patch to remove the 32GB IDE harddisk limit bug,
and made another patch to remove two additional 64GB limit bugs.
This patched BIOS supports now IDE drives up to 128GB and allows drives up to
640GB to be attached, although the BIOS will then only 'see' the first 128GB.
After booting to a suitable OS (WinXP+SP1 or later, Linux+kernel 2.4.19 or
later) the whole drive upto 640GB can be used, provided all the bootup code
is present in partition(s) below the 128GB boundary.

I also fixed the UDMA mode bug when using ATA/66 and faster IDE drives.
The BIOS now limits the reported transfer speed to UDMA mode 2 on these faster
drives, the maximum for this chipset.
This allows Win98 to enable DMA mode correctly.

For all other functions, the patched BIOS is identical to the original PX5_GP,
so you don't have to clear the CMOS if you upgrade from this BIOS.

CAUTION:
Before installing a Low Vcore CPU like the K6-2(+)/III(+), read the enclosed
CAUTION.TXT file for the correct procedure, to avoid damaging the CPU.

The filename of the patched BIOS is PX5_J3.BIN and you can flash it with
the flash program you normally use to flash a AX5/PX5 BIOS upgrade.
Please take the usual precautions when flashing your BIOS.

Note that, although this patched BIOS has been tested on an AX5 and PX5
system without any problems, it is provided "as is" and you use it
at your own risk.

I like to thank everybody who participated in testing this BIOS.
Jan.

Homepage: http://www.steunebrink.info/
E-mail  : J.Steunebrink@net.HCC.nl

------------------------------------------------------------------------------
Revision history patched Abit AX5/PX5 Ver 'GP' BIOS:

10/20/2026 patch J.3; public released
- Removed the Speed Error Hold function to allow stable CPU operation at
  speeds above 333MHz
- Fixed the Win98 UDMA mode bug
- Updated the 32GB HDD limit bugfix so IDE drives up to 640GB can be atached
- Fixed a second 64GB limit bug so the IDE HDD Auto Detection menu selection in
  the BIOS doesn't hang anymore on >64GB drives.
- Added x6.0 multiplier support for the K6-2CXT/K6-2+/III(+), in CPU SOFT menu.
- Added x2.5/x3.0/x3.3/x3.5 multiplier support for the WinChip 2A
- Added x3 multiplier support for the Cyrix Cx686(L).

02/02/2004 patch J.2; released for testing only
- Changed the CPU SOFT MENU so that 2.4v, 2.2v, and 2.1v Vcore selections are
  now available. These new selections replace the old 2.7v, 2.5v, and 3.2v.
- Changed the CPU SOFT MENU defaults to set the correct 2.4V/2.2V/2.1V Vcore
  voltage for each AMD K6 model 7, K6-2, K6-III, and K6-2+/III+ CPU.
- fixed the first 64GB HDD limit bug for 128GB IDE drive support.

06/27/2003 patch J.1; released for testing only
- Added K6-2, K6-III, and K6-2+/K6-III+ support, including Write-Allocation
  and x4, x4.5, x5, and x5.5 multiplier support.
  The CPU SOFT menu is unchanged and supports a lowest Vcore of 2.50V.
- Added 450MHz and 500MHz CPU speed support
- fixed the 32GB HDD limit bug for 64GB IDE drive support.
