Dreamcast - Is it possible to reflash the original chip?

[crimsonnight]

I'm trying to get rid of the GD ROM drive, and I know that you can flash Dreamshell so that it boots straight into it, but can you do so over the standard chip, or do you have to buy a custom modchip/do any hardware modifications?

 

[DaFixer]

You mean to flash the bios chip?
If so that is not possibile, you only change the region. If you want to reflash the bios you must piggyback a eeprom on the bios chip. Then you flash it with a region free bios.