Intel is planning to upgrade its Celeron M 520 CPU by giving it a shrunk-down core. The Celeron M 520, which is a low-cost entry-level mobile CPU based on Core microarchitecture, has been with us since January and costs $134. It has a "fully fledged" Merom core with the current B2 stepping. The new core is simply more efficient to produce and of course cheaper.
In the recent PCN 107423-00 Intel notified its customers that the Celeron M 520 will shift to a new Merom-L core with A stepping.
Customers will need a BIOS update along with a microcode update to support the CPU correctly. Besides Intel notes that "Merom-L A stepping material has minor die size decrease due to manufacturing optimisations to increase product availability".
More here - pdf.