    Chaintech 5TDM2 jumperless motherboard BIOS Revision 07/20/1998
    with patch J.3 for AMD K6-2, K6-III, K6-2+/III+, IDT WinChip 2(A)(B),
    and Cyrix MII x4 multiplier support,
    and for IDE HDDs up to 128GB (32GB bugfix).
    03/19/2026
    by Jan Steunebrink

The latest BIOS upgrade from Chaintech for the 5TDM2 is Rev. 07/20/1998.
This BIOS does not support the (mobile) K6-2+/III+ CPUs.
Also the original K6-2/K6-III and WinChip 2 are not fully supported.

To overcome these problems, I have patched the 07/20/1998 BIOS to include proper
recognition and handling of the K6-2CXT, K6-III, K6-2+/III+, and WinChip 2.
I've made the following changes:
- Added detection of the K6-2+, K6-III+, and WinChip 2(A)(B) CPUs
- Added detection of the Cyrix MII when set to x4 multiplier mode
- 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+, K6(tm)-III+, and IDT WinChip 2 strings
- Added 6.0x83 (500MHz), 5.5x83 (458MHz), 6.0x75 (450MHz), and 5.5x75 (412MHz)
  CPU speed support for the K6-2CXT, K6-III, K6-2+ and K6-III+
- Expanded the SeePU & CHIPSET SETUP menu's single 2.2V Vcore selection for K6-2
  to 2.0V/2.1V/2.2V/2.3V/2.4V/2.5V selections for all low Vcore CPUs
- Enabled the SeePU & CHIPSET SETUP menu's x4.5/x5.0/x5.5 multiplier selection
  for any CPU, to benefit extended selections for the WinChip 2(A)(B).
  But note that some CPU models don't support these higher multipliers,
  or translate them to another setting
- Fixed a bug that prevented the correct functioning of the SeePU & CHIPSET
  SETUP menu's x5.5 multiplier setting.

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 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 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 Rev.
07/20/1998, so you don't have to clear the CMOS if you upgrade from this BIOS.

NOTE:
The patched BIOS defaults to a 2.2V Vcore for K6model 7 and K6-2(+)/III(+) CPUs.
After installing a K6+ CPU, enter the BIOS Setup at the first boot and set
the 'Users favorite' option to 'Enabled', and 'CPU Vcore' at 2.0V.
A K6-III CPU can be set at 2.4V the same way.
These options can be found in the SeePU & CHIPSET Setup menu.
Exit the BIOS Setup via SAVE & EXIT for the changes to take effect.

The filename of the patched BIOS is 5TDM2_J3.BIN and you can flash it with
the flash program you normally use to flash a 5TDM2 BIOS upgrade.
Please take the usual precautions when flashing your BIOS.

Note that, although this patched BIOS has been tested on a 5TDM2
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
