The first batches of the S1 Rev.2 (Like mine / Gannu ) did not have heatsinks for the VRM area of the 4850. It was included in the next batch (Like Ethan Hunt ). You just need to ensure that the one you buy isn't the older one without the heatsink.

@Mohit, do try removing the plastic cover of the card, clean the heatsink and tie a 120 / 92mm fan directly and check results. Then take the jump if necessary.