(27.09.2016 10:14)SWAT писал(а): It's not posisble, because Sega mapped only 2MB memory for this chip.
Thanks. Well that's a pity.

So does it mean that even if I flash the chip with two bios using an external programmer, Dreamcast can not access the second bank of the flash?
But I'm curious about that "start address" option on bios flasher program, how to use it? Do I need to use a hex value or what?
(27.09.2016 15:39)megavolt85 писал(а): Gillbert, please test. Connect A20 pin to GND and flash BIOS
For change BIOS use A20 pin, not connected is first BIOS, connected to ground is second bios.
I already done that. Unfortunately nothing changes when I connect A20 pin to the GND

It doesn't select the banks.
Like SWAT wrote, the problem is because Dreamcast can not reach more than 2MB address lines.