The 3800+ actually differs from the previous ‘Toledo’ X2 in that it’s based on what AMD internally calls the ‘Manchester’ core. This means that it’s been designed from the ground up to have only 512kb of Level 2 cache. With less cache and a lower clock on a 0.9mm Silicon-on-Insulator manufacturing process, the die size is down to 147mm with 154 million transistors, compared to 199mm and 233.2 million transistors on the 4800+. That makes it a lot easier to produce in high quantities from the fabs, which helps keep the costs down. It also brings down the maximum thermal power rating down to 89W compared to the 4800+'s 110W.