XOS

From t-hack.com - Hack X300T / X301T

XPU OS (name is not confirmed)

this is the bios of the system, which is embedded in the internal flash of the XPU. It is not possible to access the XOS code from the regular CPU or via JTAG.

The XOS can be updated with encrypted data that is written into a certain address range. It is assumed that the XPU will decrypt the data (maybe also check a signature) and reflash the internal flash with the new XOS version. In case of the X300T the "checkxos.exe" application verifies that the latest XOS version is installed, and an upgrade is done if necessary.

Sigma Designs provides updates of the XOS to their customers. The version of XOS is displayed during boot on the debug console.

* xosPc8 == version 1.02 
* xosPca == version 1.03
* xosPd0 == version 1.04
* xosPd2 == version 1.05
* xosPd4 == version 1.06
* xosPd6 == version 1.07
* xosPd8 == version 1.08
* xosPda == version 1.09
* xosPdc == version 1.10
* xosPde == version 1.11
* xosPe0 == version 1.12
* xosPe2/xosPe4/xosPe5 == version 1.13
* xosPe6/xosPe7 == version 1.14
* xosPe8/xosPe9 == version 1.15 (current release) 

The XOS updates mostly fix reboot issues with incorrect re-initializations of hardware, but also security issues are fixed.