Right, the only reason you upgrade processor and memory in a xbox is for emulation reasons. If your just gonna be playing ISO games there is no reason to bother as ALL games don't use the extras as they were not programmed to do so.
First recommendation flash the tsop or modchip with a compatible bios for 128mb ram like IND BIOS 5004.67 or Xecuter bios,use samsung ram chips QC-50 i recommend use new ram chips from ut source,on xbox 1.0-1.1 motherboard versions already comes with solder on the ram pads use a fiberglass pen to expose the pads so then can be easy to solder the ram to the pads on the motherboard,use plenty of flux to solder,very important the ram have a circular mark and the motherboard also has a circular mark that is the orientation,the rams that are already installed on the board let you know how the new installed ones are going,finally use the xblast os to test the ram chips.
Hi, i did it once, has been 10 years ago, i killed another board by removing all ram, then i simply soldered on the new board, but it did't recognized. but a friend wich were working with modchip told me the modchip bois must be programed with a correct flash to recognize it. i dont have it any longer, but as soon i will do it again i may update you. but this was the way i did it.
Beware, additional ram causes incompatibility issues with some Xbox games since they're not programmed to be able use them. No official Xbox game will benefit from it, if it's emulation or video playback boost you're after it's good but otherwise it's unnecessary.
Floyd did this tutorial a while ago, tells you everything you need to know. the mod isn't for the faint of heart. and it's definitely one of the more difficult mods for the Xbox. so make sure your soldering skills are up to the task. even if you think your good at soldering you may find out the hard way that you aren't... I killed many Xbox's, I did eventually end up with a 128mb Xbox but i didn't successfully accomplish it myself.