Does BIOS mod need bridge between R512 and 12v?

[darthcloud]

Finaly got it to work!!

I switched MX chip supply from 5v to 3.3v and now it work, I was able to flash the bios

So it look like the DC bus can handle both 3.3v and 5v logic as '1'. And the MX chip can handle 5v as '1' too.

I bit hacky but it work.

Thanks for help.

EDIT: Did a shematic for older DC