By dissecting technical documentations of new MacBook Polycarbonate we note the similarity of the placement of the components and also the shape of the mother board compared to MacBook Unibody. To illustrate these observations, here are two photographs taken from the site of iFixit.
On the left is the mother board of MacBook Unibody Alu 2008 and on the right that of the polycarbonate unbody 2009. As you can see, the shape, the position of the CPU and of the chipset are identical. There are some differences at the level of the connectors, the power supply and the stabilization of the current, but nothing significant. One can note that Apple cut down on certain components to further reducer the cost of the mother board.
For those who do not need Firewire, this Macbook 2009 is an excellent machine whose power will be enough for the majority to the users who look for low-cost portables.
