I just glanced at the article that TMM provided and the original config of that computer was an 800mHz which means the logic board is the older one. I suspect yours has a completely different architecture and that's why you can't find the specified jumper.
BTW, the USB 2.0 eMac with a 1.0G processor is a special model sold only to the education market. Most 1G eMacs have the older logic board. In looking for articles on overclocking, you'll need to find one that talks about the 1.25 and 1.42G units; they share the same logic board as yours.
That also means that a RAM selector on a vendor's web site will often report a 1G eMac as taking PC133 RAM. If yours is really a USB2.0 (System Profiler will show it as "powerMac6,4') you need the PC2700 RAM that the faster eMAcs use. With modern RAM modules, the 6,4 machines can use 2 x 1G sticks for a total RAM of 2GB. Just be sure to order the RAM from a Mac-savvy vendor like these:
eMac RAM at Other Oorld Computing
eMac RAM at Data Memory Systems
I bought a 1G stick for my wife's eMac 6.4 from the first vendor--works great.
