Tutorial written by : Regionfree (http://www.xbox-hq.com - posted here with permission of author)

This is a tutorial on how to make your own homebrew dual bios idiot-proof modchip.

The reason I decided to come up with this is because I, like a lot of other people, like to experiment with different bioses. Like a lot of others, I’ve had bad flashes where the chip has to be connected to the programmer, connect to the pc so on and so on. Waste of time. You’ve got your 1meg chips where you can have 4 different bioses, same as a TSOP flash, but if you stuff that up, you have to revert back to the programmer again. In short, this chip gives you one flash protected chip which you can’t stuff up, and one flashable which you can stuff up as many times as you like. For some enterprising people, you can even have the Linux bios on the flash protected (backup chip), so you can legally sell it.

You need,

- 2 x SST49LF020
- 1 x dual ON/ON (3 way) switch
- Some Kynar wire 30AWG
- Some solder
- Soldering iron
- Soldering skills etc

First thing you need to do is flash one of the chips with the bios of your choice.
Then strip about 50mm of wire and solder each of the chips as shown in fig. 2,4 & 7

Front of (Back up chip)

Back of (Back up chip)

Once you’ve soldered all the pins as per the diagrams, using some double sided tape stick the chip (Backup chip) on top of the other chip (Flash chip).

With the 30AWG wire, connect the colour pins together as shown in fig. 3,5,6 & 8.

Take care, not to solder the red and yellow pins together. Try and keep all the wires as short as possible.

Connect red wire #1 to pin #1 on switch, red wire #2 to pin #2 on switch, yellow wire #3 to pin #3 on switch and yellow wire #4 to pin # 4 on switch.

From pin #5 on switch connect to #5 on mother board and pin #6 on switch connect to #6 on mother board.

Again you have to keep these wires as short as possible. Keep switch as close to the chip as you can.

Solder the rest of the wires to the corresponding points on the mother board.

To flash the chip, enable the (Backup chip) with the switch for just a couple of seconds and than switch it over to the (Flash chip). Once you’ve booted to your Evox dashboard, just flash the chip as normal.

If you want to use the OzXflash sofware to flash with, you have to keep the (Backup chip) enabled till the program starts to load before switching over to the (Flash chip).

If there is a positive response from this tutorial, I may assemble a code for a Pic to switch over the chips instead of the three way switch.

Front of (Flash chip)


Back of (Flash chip)

Three way switch

On mother board

HOPE SOMEONE GETS SOME USE OUT OF THIS COS I HATE DOING ALL THESE DIAGRAMS.

IF THERE ARE ANY PEOPLE OUT THERE THAT WOULD LIKE ONE OF THESE CHIPS BUT IS BEOND THEIR CAPABILITY, CONTACT ME AND I MAY BE ABLE TO HELP YOU OUT.

IF I HAVEN’T MADE SOMETHING CLEAR ENOUGH, CONTACT ME AND I MAY BE ABLE TO HELP YOU OUT.

CHEERS, REGIONFREE