Hacking Oldies Info about Dreamcast 4-wire modchips

[SylverReZ]

(credit: link)

I've been very curious about this '4-wire' modchip that are found in early Dreamcast models that I have very little information about; aside from diagrams and photos for what the chip looks like (being a CPLD logic device) I cannot seem to find anyone who had reverse engineered the logic as to how it works. The chip went under "Dreamchip" amongst others. Most of the points seem to be soldered to the RAM chip, to which I suspect it's patching RAM in such a way where the BIOS is loaded to enable region free capabilities.

Links:​

Dreamcast BIOS Hacks - https://web.archive.org/web/20230429124333/https://dreamcast-talk.com/forum/viewtopic.php?t=6312
Dreamchip Installation - https://www.angelfire.com/super/modking/bin/install_a_4_dreamchip_2.htm

 

[master801]

The best I could find is this: https://dcemulation.org/phpBB/posting.php?mode=quote&p=724980&sid=d3fac8cfd4be944fcefaf341f4fe533c

Basically as you said, it just patches the BIOS when it's copied to RAM. And it's very specific, so if you don't have the same exact BIOS as it expects, it errors out.

 

[SylverReZ]

The best I could find is this: https://dcemulation.org/phpBB/posting.php?mode=quote&p=724980&sid=d3fac8cfd4be944fcefaf341f4fe533c

I have to logon to view the post. Can't be bothered with that unless I have to tempt myself with using a disposable e-mail.

 

[master801]

I have to logon to view the post. Can't be bothered with that unless I have to tempt myself with using a disposable e-mail.

My bad.

It seems that DCEmulation doesn't have a perma-link feature for posts

https://dcemulation.org/phpBB/viewtopic.php?t=67196