Why
Some users use the Xbox for a full graphical desktop environment, such as Gnome or KDE. While the Celeron 733 is more than adequate for running these, the 64MB of RAM greatly slows the system down and it spends a lot of time swapping to disk. Also, users of MAME or other emulators may experience similar problems.
What you'll need
1. An Xbox (Xbox 1.6 versions do not have the 'spaces' for attaching the extra RAM chips, so they aren't suitable.)
2. Four of the RAM chips the Xbox uses. - See end of article for info on suppliers.
3. A soldering iron (15W - 25W with pointed tip around 2mm) + solder (26SWG with Flux).
4. Solder wick (braid).
5. Magnifying glass (x20 recommended!) / a pair of jewellers' loupes.
6. A very bright area to work in or an anglepoise lamp to point at your motherboard.
7. A steady hand!
8. Cromwell Linux bios version 2.26 or greater. Linux does NOT support 128MB of RAM via Xbeboot at present.
9. An up-to-date Linux kernel using xboxfb, not rivafb. If too old a kernel is used, you will get no video output (just flickering white/black lines) until you update the kernel. Xebian 1.1.0 works ok (Tested on v1.4 Xbox, Cromwell 2.32)
Installing the extra memory
1. Take the Xbox apart and remove the motherboard (See OpeningXbox for details)
2. Locate the four empty memory chip spaces on the motherboard (Two on top, two on underside).
Look at the orientation of the nearest memory chip to the empty space. (Orientation on these chips is determined by the small circle/large circle markings on opposite corners). Orient your chip to match the orientation of its nearest companion. As a way of double checking, there are markings of pin numbers (1-100) printed on the PCB around the pads. Check that these also match on both the empty space and its nearest companion to ensure that the orientation should be the same. (On the 1.3 Xbox I worked on, this WAS the case).
The actual soldering technique I used is sourced from here:
Numbnut's SMD soldering guide (
Cheaptag), or as he puts it, Become a fearless soldering God.
Here are some photos showing the various stages of installation of a chip:
Tacking down two opposite corners of the chip:
Drowning the chip in solder:
The chip, after using the solder braid/wick to remove the excess solder:
After you've removed the excess solder, check for loose pins (ie ones which are not completely fixed down) by running over them gently with a screwdriver tip (VERY FINE). If a pin is not soldered properly it will move slightly. Once identified, push it back straight with the screwdriver tip, and resolder it down.
When you're happy no pins are loose, give the chip a clean with a flux cleaner, to make it easier to see bad joints.
The next stage is to check for shorts with a magnifying glass and a multimeter. This can be difficult due to the size of the tips on your multimeter probes. DON'T use the Diode Test function of your meter as you will think you have hundreds of shorts - the better option is to use the resistance function as sometimes there is only 30 ohms between two pins. Measure the resistance between a pin and it's immediate neighbour all the way round the chip, if you find resistance of less than 1 ohm you definately have a short. Check the pins with your magnifying lense - sometimes you can see the short sometimes you can't. Usually it is sufficient to heat the pin up concerned with your soldering iron briefly and the solder will run back into the join. If the pin looks ok check the same position on the other three chips as they all share the same address positions ie Pin 1 = Pin 1 on all the other chips, Pin 2 = Pin 2 etc. When you're happy that everything is fine (checking takes longer than the soldering itself) put the xbox motherboard back in, connect up the drives and turn it on!
Typical resistance values between adjacent pins are:
30 Ohms 150 Ohms 300 Ohms 1.5K Ohms
Anything below 20 Ohms is worth looking at - if the resistance doesn't change you are OK.
If all is well, you'll be greeted by cromwell confirming you now have 128MB RAM.
However, all may not be well. If you get red/green flashing, or the Xbox powering off after three seconds, you most likely have a short still. It took me many attempts to find all the shorts, and get the Xbox to boot. The good news is that in my case that these shorts did not permanently damage the Xbox, and when they were fixed, it booted up fine. However, to be safe, I would recommend checking and rechecking before applying power.
Good luck!
Upgrading Xbox RAM HOWTO
Upgrading Xbox RAM HOWTO 
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