If you're wanting to install extra ram for morrowind, I wouldn't even do it. If you have 128mb ram and you patch the xbe to use it, then from what I've seen your game gets choppier, and even eventually freezes over enough play time. For whatever crazy reason, more ram only seems to slow down and eventually freeze this game. That's right. It could be that it's freezing near the time it reaches above 64 mb in ram, which seems about accurate. It could be that the game is 'not optomised' for double ram, whatever that means. I know it sounds conflicting that it doesn't have a positive affect. Apparently though, it's possible by just adding ram to slow down, screw up, and remove all stability from a game. Something could just be wrong with my ram, but then I don't even think it would register on dashes.
Long story short, extra ram is good if your focus is emulators. The extra ram can actually allow you to load roms you otherwise couldn't. However, I reiterate that if you want to get extra ram just for morrowind, it's probably not the best idea. If you end up trying it anyway, or someone has a different experience, post your findings by all means.
But you can run roms larger than the 64 megs of the xbox, i have run metal slug 5 who is, unziped, 90 megs. Is there any rom larger?, i run it with mameox.
The extra ram will be useful to if you run linux on the xbox.
Sorry for the english.