OS/2 recognizes only 64MB on new mainboard

When using more than 64MB RAM the operating system IBM OS/2 only recognizes the lower 64MB, while using the BIOS option 'Boot to OS/2 > 64MB' only the lower 16MB. Why that ?

OS/2 uses INT15h AX=801h to determine the RAM size during bootup.
Some new BIOS releases only support the INT15h AX=820h (like DOS / Windows use it) instead of both.

You can find a patch for the OS/2 Warp 4 bootloader here: