It's kind of lame, but it was clear within weeks after launch that the original iPad was gimped for RAM. Apple manged to make it bearable for a while, but iOS

It's kind of lame, but it was clear within weeks after launch that the original iPad was gimped for RAM. Apple manged to make it bearable for a while, but iOS 5 on the original iPad has always been hitchy with a crashy Mobile Safari, so it's no surprise that iOS isn't going to be supported.