Apple has released two new updates for the Late-2013 iMacs just introduced this September. The first update is a firmware upgrade that is only for the new iMacs with Flash storage, while the second update is a supplemental update to OS X 10.8.5. The details:
iMac SMC Firmware Update 1.1
This update is recommended for iMac (late 2013) with flash-only storage. This update improves the Power Nap feature in Mavericks on your flash based iMac by allowing it to perform silently, without spinning up the fan.
Power Nap periodically updates apps, such as Mail, Contacts, and Calendar, and will download software updates while your iMac is sleeping.
iMac 10.8.5 Supplemental Update 1.0
