The following is a guide for identifying and determining the official PCB revision of an original Xbox motherboard.
Whereas other guides do exist, they use made up community "revision" numbers, and most list "revisions" that simply don't exist.
This guide aims to be a (albeit futile) attempt at fixing public knowledge and showcasing the official Microsoft revision system.
There are 3 unique retail PCBs, other PCBs do exist but they were prototypes or dev/debug hardware and were never sold to customers.
This guide will only show retail revisions for simplicity, as well as for the fact that's what the general user will have.
There are a variety of ways to identify what revision you have, each with different levels of accuracy, I will be showing 2 in this guide, as well as showing various bits of info about the 3 boards.
If you have access to the motherboard, the easiest way to identify it is to simply look at the PCB revision markings.
On 009 boards it is located in the bottom right of the back side of the board.
On 012 and 121 boards it is located in the top right of the back side of the board, right next to the IDE header.
The first 6 characters are likely to be the internal part number designation (121 was a cost reduced re-release, which would explain it being different), and the last 3 characters are the PCB revision designation.
The following diagram shows where they are located:
If you want to identify revision without opening the case you can easily do so using the serial number.
It is the least accurate of the methods in this guide, but it is a pretty adequate best guess if you are currently unable to open the console.
The serial number can be found on a sticker on the underside of the console, it is formatted as shown:
XXXXXXX YWXXX
The 8th and 9th digits are the last digit of the year, and first digit of the week in the year respectively.
Using this you can roughly identify the motherboard PCB as follows:
If YW is 25 or less, it is likely a 009 PCB.
If YW is more than 25 but less than or equal to 33, it is likely a 012 PCB.
If YW is more than 33, it is likely a 121 PCB.
There are 3 different GPU revisions.
009 used XGPU*
012 used XGPU S
121 used XGPU-B
There are currently no known differences between the XGPU and XGPU S revisions.
XGPU-B received a dieshrink from 150nm to 130nm and its core voltage dropped from 1.5 to 1.375V, reducing its power draw and consequently lowering the heat it generates.
All GPU revisions are pin compatible and electrically compatible, but XGPU-B doesn't appear to be compatible with older kernels.
*Some amount of 009 boards have been found that have an XGPU S, but it appears to be *extremely* uncommon.
