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[DEV] : MOD Dreamcast REV0 (Va0) with GDEMU

Xrider

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Hello,

Just a little message to let you know that the Dreamcast Rev0 curse (Va0 motherboard) with GDEMU has been lifted for the first time, and the mod is MADE IN FRANCE
Yes, this is a world first to my knowledge

Small video:
http://delta.island.online.fr/partage-darius/Dreamcast-Rev0-GDEMU/IMG_2964.MOV

The Techniques:

The Va0 (Rev0) motherboard has a logic level of 5V on the G1 bus

On this G1 bus of the Va0 we find:
- The GDROM (logic level and 5v power supply)
- The Bios (logic level and 5v power supply)
- Flash memory (logic level and 5v power supply)
- Holly, the Dreamcast GPU (5V and 3.3V tolerance)

The other motherboards of the following revisions (Rev1 and Rev2) work with a 3.3V logic level on the G1 bus
The GDEMU was designed for the Rev1, they represent the vast majority of Dreamcast

On this G1 bus of the Va1 we find:
- The GDROM (logic level and 3.3v power supply)
- The Bios (logic level and 3.3v power supply)
- Flash memory (logic level and 3.3v power supply)
- Holly, the Dreamcast GPU (5V and 3.3V tolerance)

Here is an extract from the Dreamcast service manual representing the G1 bus:



To do this, here are the components to use:

BIOS: MX29LV160
FLASH: MX29LV002

It will therefore be necessary to unsolder these two components and pre-program the two memories (MX29LV160 with a bios, I recommend Japanesecake 1.02 https://japanese-cake.livejournal.com and the MX29LV002 with the dump of your old flash memory).

Then you have to install the two components, lift the power pins, and connect them to a 3.3V point (and yes, otherwise they will take 5V and they will not like ... lol)

Then on the front of the CM, remove component D503 and make a strap:



Good news, region changer now works on Rev0 without adding a shunt or anything else!

WARNING :
The original 5V GDROM reader will be incompatible after modification!
Use only the GDEMU or a 3.3V reader found in the Rev1
 
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darcagn

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Good news, region changer now works on Rev0 without adding a shunt or anything else!
This is not a good idea to be left like this, as software may write to the flash and brick the console. The Sega DC checker software for example clears the flash and will also clear (and brick the console) factory region coding if this mod has been performed. I don't know how widely used it is, but I myself do use it to check DC consoles I handle. Other software may do it too

MX29LV002 supports protecting specific sector ranges just like the original DC chip does, might be better to wire it up to protect the 8K partition 0 at $1A000 if it is possible
 
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