QUOTE(Allegro1 @ Feb 6 2006, 07:20 PM)
You actually CAN run 2x256k + 1x512k BIOS's this way:
1 DPDT switch, call this SW1
1 SPDT switch or a second DPDT switch, just use one pole, call this SW2
Common1 goes to A19
one side goes to Vcc, the other goes to GND
Common2 goes to A18
one side floats, the other side goes to the common of SW2
one side of the switch goes to Vcc, the other goes to GND, the common is the one attached to SW1
This way, when SW1 switches A19 to Vcc, A18 floats and can do whatever the cpu calls out and you have a 512k BIOS.
When SW1 is grounded, A18 will either be driven to Vcc or GND depending on SW2 to swich either of the 256k BIOS's.
This way, there are no illegal states, and so long as you print up a legend and tape it to the box, you'll know what you are doing.
Anybody can confirm that working fine?
Sorry for that but I have one broken xbox via tsop flash