Microsoft has updated and released cumulative firmware and driver pack for Surface Pro. It includes the latest version of the firmware and drivers, required for Surface Pro, in a downloadable zip format. These drivers are in the INF file format and can be installed without requiring an executable. The pack includes firmware that is delivered in the form of a driver package.
This firmware and driver package contains drivers for all of the components in the Surface Pro device, as well as updates to the system firmware that have been released via Windows Update.
To update the firmware manually simply install the driver package on the machine then Windows will then seamlessly take care of the update process for you, ensuring that the correct firmware is applied.
You can use these drivers and firmware to prepare your custom images for enterprise deployment, or to repair problems with custom installations of Windows 8 Pro on your Surface Pro device.
Surface Pro firmware and driver pack
Download page.
Do note that these drivers and firmware are meant for Surface Pro and are not compatible with Surface RT.