Hacking the Xbox

Chapter 10 - More Hardware Projects 157
suspiciously like the spots currently occupied by memory chips. Flip the
board over, and there are two more unoccupied chip footprints. These
empty footprints are in fact for memory chips. The location of these blank
spots is shown in Figure 10-2.
The next logical question is, of course, “Can you double the Xbox’s
memory size to 128 MB by soldering suitable memory chips into the open
slots on the Xbox motherboard?” The answer is in fact yes, but the
initialization code for the Xbox needs to be modified in order for the
chipset to recognize and use the extra memory. In addition, the extra
memory does not help graphics or gaming performance. Xbox games are
not designed to take advantage of the extra memory, so the extra memory
will typically sit around unused. The extra memory spots are provided
primarily for the manufacture of special consoles for game developers.
Game developers can use the extra memory to ease the transition of games
into the Xbox’s relatively tight memory footprint, as well as for keeping
debug, performance monitoring, and test utilities resident in memory that
are not part of the game image. Note that the extra memory could be
leveraged by home-brew software, but the difficulty of obtaining and
installing the memory chips makes Xbox memory expansions more of an
interesting soldering practice exercise than a practical modification.
Xbox VGA
There is a little bit of confusion about what an Xbox VGA adapter does.
Many Xbox VGA adapters are actually TV-to-VGA converters. In other
words, they take the low resolution TV output from the Xbox and run it
through a line doubler to yield a low-quality VGA display. A true Xbox
VGA adapter actually configures the Xbox to output a much higher
resolution video output, yielding a better-than-TV quality display on a VGA
monitor.
The VGA adapter configures the Xbox graphics mode using designated
pins in the AVIP (Audio Video I/O Port) connector. The main problem
with this approach is that a game has to be specially written to support this
higher resolution mode. As a result, some games will not work with a true
Xbox VGA adapter, but fortunately going back to TV resolution is as easy
as plugging in the standard TV adapter cable.
The original Xbox-VGA adapter was developed by Ken Gasper. He sells a
version of it on his website at http://xboxvga.xemulation.com.
Currently, he offers the Xbox-VGA adapter in a “bare board” form as well
as in a fully assembled form. If you are looking for an interesting hardware
hacking project for the Xbox that is both useful and will hone your circuit
assembly skills, it may be worth purchasing one of his bare boards and
attempting to assemble the adapter yourself.
Appendix F contains a pin diagram of the Xbox AVIP.