Form Factor And Compatibility
Mobile Athlon 4 will come in two different form factors. One of the two is the well-known SocketA form factor, as shown in the pictures above. AMD claims that Mobile Athlon 4 cannot be operated in a normal SocketA motherboard, although Mobile Athlon 4 for SocketA has got the same mechanical dimensions and pin count as previous SocketA processors.
Supposedly some of the pins have 'different assignments'. I can NOT verify this. What I found however is that a few pins of Athlon 4 are now used that were marked as 'not connected' for Thunderbird Athlons.
Two of those pins are the above-mentioned pins for the thermal diode. Besides that there are five pins for Mobile Athlon 4's clock multiplier SVID[0..4] and one pin that is called CPU_PRESENCE# (AK6).
Those pins might be an issue when sticking Mobile Athlon 4 into a normal SocketA motherboard, but it might as well not be a problem.
The other, probably preferred, form factor for Mobile Athlon 4 is an ultra-low profile, small footprint Organic Ball Grid Array (OBGA) package, optimized for thin and light notebooks.
Unfortunately I couldn't find any pictures of this package, but I am sure that AMD will soon provide some.