We offer used mainboard / logic board for the iMac 21.5" A1311 Late 2009. The logic board setup is with:

- 3.06 Intel Core 2 Duo CPU 

Details:

Apple Parts number: 820-2494
A1311 - 21.5" - late 2009 - emc 2308

Correctly working. We also have parts for other models.