I found a great tool for PS3 Linux that uses a single SPE to zoom in on the center of the screen by a factor of 2X, 3X, or 4X. This helps when running many different games or emulators since you can run at the original resolution (much faster than scaling done by the application) and the scaler tool, using one of the SPEs, takes care of enlarging it.
Here’s where you can get the source (translated page): link to “miya’s Diary” post
Applications I have used it with so far are Quake 2, QEMU running Windows 95 / Diablo-Hellfire, VICE (C64), snes9x-gtk, and sdlmame. Screenshots can probably explain this better than I can, so …
snes9x-gtk running a game at the original resolution:
about to start scaler:
photo of scaler running — snes9x-gtk is still running the game at the original resolution, but scaler has zoomed in on the center of the screen (3X):
Here’s one way to set it up … download the scaler.tar.gz file (which includes source & a binary), save to your desktop and extract it, then copy the included scaler binary to your /usr/local/bin folder:
cd ~/Desktop
tar -xvf scaler.tar.gz
cd scaler
sudo cp scaler /usr/local/bin
Or to compile it on YDL 6, just enter make from the scaler folder. I had to install some additional development libraries on my system — this might take care of getting them all: yum install *spu* *ppu*
There are many different ways this tool can be used … for example, you can include it in a script to start Quake 2 like this:
#!/bin/sh
scaler -s 3 -t 3000 & quake2.sh
killall scaler
The -s switch tells it how much to scale, and the -t switch tells it how long to run. Running Quake 2 at 320×240 on a 1280×720 screen would normally result in the game screen being very small, but fast (about 150 FPS 94 FPS timedemo) on the PS3. Using scaler you can run it at 320×240 with 3X scaling so it displays at 960×720 and still runs at 150 FPS around 90 FPS (timedemo test), whereas if you run Quake 2 normally at 960×720 you get around 25-30 FPS. Or course it looks better when Quake is actually running at 960×720, but the additional speed you get from running it at 320×240 and using scaler is great!
Or you can set it up so you can zoom in on the screen at the press of a key using custom keyboard shortcut commands in GNOME. See here for info on setting up custom commands:
Create custom keyboard shortcuts in Linux
EDIT: You’ll need to install gconf-editor for this — yum install gconf-editor
I set mine up so I can use F9, F10, F11, and F12 to scale 2x, 3x, 4x, or turn scaling off.
EDIT: Hmm… it seems that was a poor choice of keys, though… 
EDIT: Here’s a post that describes how you can set up the keyboard shortcuts for the scaler tool in more detail:
http://pleasantfiction.ipower.com/bodega/viewtopic.php?p=735#p735