How too unlock GD-ROM drive?

How to unlock GD-ROM drive?

I has changed original dreamcast bios, instead of IC 501 mask rom has connected flash microcircuit.

But with changed bios does not work GD-ROM drive.

The data read from ROM are passed through some type of "checksum".
(is used port 0xA05F74E4)
Unless a specific value is computed, a flag is set to disable the GDROM drive.
Sega must have put this in there to "discourage" people from replacing the BootROM with
their custom versions.


How to unlock GD-ROM drive with changed a bios?

p.s. strange, but modified bios
Hybrid from devkit and dc bioses work, see video

 

What sort of flash do you use ?

And, what sort of bios do you put on this flash chip ?

 

example
changed texture, animation, sound.

 

nice one to change the bios we could make our own dreamcast 2 would be nice if we could get the gd rom part working

 

Hi Sundragon

I can't se ethe video you psoted, the website says error 404.
Good luck on hacking the bios!

FG

 

Hi
I has corrected link

thx

 

WOW, if that vid is true, than this may be amazing!!!

 

This vid is true. It's amazing :dance: !

FG

 

So, is this fully working? Is it possible to do it without any devkit, if yes, can you tell us how?

 

hi i saw the video to me it work fine but will it work with shenmue

 

Well, he replaced his bios with a modified HYBRID bios, which got parts from the retail one, and parts from the devkit one. It's possibly region free too. Link83 released an hybrid bios some time ago that had the devkit intro animation, was region free, and worked with mil-cd, he couldn't try if it loaded gd-r though.

AFAIK SunDragon is trying to modify the bios further than merging part of different ones, he tries to modify the text and images within it.

FG

 

How can we apply this Link83 bios thing to our DCs? Using a bba? Any lil tut»?

 

you will desolder the existing BIOS chip, and replace it with another memroy chip that has the new BIOS burned on it ?

 

Basically yeah, but I think it's also possible to "disable" the original chip and simply solder the new one "over" it. I think that the guy who made the DC-NAVI did (kalistios author, Dan Potter).

However this would be an easier way to do it, physically swapping the chips would works for sure.

FG

 

i got to get my uncle to programe me the chips and cant wait to see this it looks cool on a retail i have a spare dc or two to try this on but frist i need to know what type of chips i need i know they need to be smd kind

 

PSOP 44 chip like AM29LV160 but it's hard to find 2 mbytes chips with PSOP 44 and support only 3.0 volt

You can get more info from l_olivera