Hold your horses, mister. If you want a reliable flashcart, don't go for the chinese clones - they all
suck and they're not worth the money you're saving. Get a genuine Everdrive GB, the cart is excellent, I
reviewed it myself. Support the creators, not the imitators. If you wouldn't buy a
"Zony" TV rather than a Sony TV, you shouldn't buy an
"Eberdrive" instead of an
"Everdrive" if you want quality.
If you want to make a
proper DIY GB cartridge I suggest browsing
this site, it has
everything you need to know including schematics and software. It doesn't take much, all you need is a cartridge with a desirable mapper, a compatible rewrittable memory module, a soldering iron and some patience. It even has schematics for cartridges that can be made completely from scratch.