   PCChips M577/Amptron PM9900 motherboard BIOS Release 03/09/1999 S
   with patch J.4 for AMD K6-2/550, K6-2+ and K6-III+ support,
   and for IDE HDDs up to 128GB (32GB bugfix).
   10/14/2023
   by Joszef Csongradi and Jan Steunebrink

At this moment, the latest BIOS upgrade from Amptron for these boards is the
version 990309. Except for some minor differences to improve performance, this
BIOS is the same as the version 990306S from PCChips.
This BIOS does not support the (mobile) K6-2+/III+ CPUs.
Also the original K6-2/550 is not correctly supported because this BIOS
doesn't support the 5.5 x 95 (523 MHz) and 5.5 x 100 (550 MHz) speeds.
To overcome these problems, we have patched the 990309 BIOS to include proper
recognition and handling of the K6-2/550 and K6-2+/III+.
The following changes were made:
- Added detection and correct CPU Type display for K6-2+ and K6-III+
- Added support for CPU speeds above 500MHz for all multiplier/busspeed
  combinations upto 6.0 x 100.
- Expanded the automatic enabling of the K6(-2/III) Write Allocation feature
  to work also on the K6-2+ and K6-III+
- Expanded the K5/K6 busspeed/multiplier/CPU speed detection to work for the
  K6-2+ and K6-III+ upto 600 MHz CPU speed.
- Several (previously hidden) CMOS SETUP options have been enabled to allow
  better control over the various chipset features.

In addition we have made a patch to remove the 32GB harddisk limit bug, and
made another patch to remove two additional 64GB limit bugs.
This patch J.4 BIOS supports now IDE drives upto 128GB and allows drives upto
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 (Jan) also fixed the UDMA mode bug when using ATA/66 and faster IDE drives.
The BIOS now limits the reported tranfer 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 BIOS,
so you don't have to clear the CMOS if you upgrade from a 990309 BIOS.

The filename of the patched BIOS is 990309J4.BIN and you can flash it with
AWDFLASH 6.28, like any other M577/PM9900 BIOS upgrade.
Although PCChips and Amptron packed Awdflash 5.34 with their previous BIOS
releases, I recommend using Awdflash 6.28 for both boards.
Please take the usual precautions when flashing your BIOS.
Refer to Amptron's web-site at
http://www.ampron.com/html/bios.html
for the proper flash procedure.
The AWDFLASH 6.28 program can be found in this zip-file.

Note that, although this patched BIOS has been tested on different M577/
PM9900 systems 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, and
especially Joszef for doing the major patching work on this BIOS.
Jan.

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