
The Yonah processor still uses 479 pins but uses a slightly different layout so it won't fit in current Pentium M motherboards.
But likely this won't be such a big problem as manufacturers will need to develop new Yonah compatible motherboards because this new mobile processor has higher power requirements. But it may be a problem for enthusiasts why have built a Pentium M based HTPC, they won't be able to upgrade their system to a new Yonah processor without buying a new motherboard too.