3's graphics chip RSX), yet some access to the RSX graphics processor was achieved (but Sony blocked this with firmware release 2.10). As of firmware release 3.21, consumers are no longer able to access the 'Other OS' due to Sony removing the facility from the software in an update. Sony said this was in response to several 'security concerns'. Homebrew developers do have access to the Cell microprocessor, including 6 of its 7 active Synergistic Processing Elements (SPEs). The Game OS resides under a hypervisor and prevents users from taking full control of the PlayStation 3's hardware. This is a security measure which helps Sony feel secure enough to allow users to install other operating systems on the PS3. The Sixaxis controller has also been exposed to Linux and Windows, but no driver seems to have been successfully created yet that exposes its accelerometer functionality, except for Motioninjoy. However other drivers have successfully used it as a controller for gaming and other applications. In May 2008, a vulnerability was found in the PlayStation 3 allowing users to install a partial debug firmware on a regular console. However, the debug functionality is disabled, so neither homebrew applications nor backup games can be run yet. Another exploit was found on August 14, 2008, allowing users to boot some backup games from the PlayStation 3's HDD, although the exact instructions on how to do this were not released at that time. However, a different person posted instructions 10 days later, which explained the exploit. On January 6, 2009 a hacking ring known as the "Sh4d0ws" leaked the jig files needed to launch the PlayStation 3 into service mode. Although the PlayStation 3 can be triggered into service mode, it is not yet of any use because the files needed to make changes to the console have not been leaked. On August 31, 2010, PSGroove, an exploit for the PS3 through the USB port, was released and made open source. This exploit works on all of the PS3 models released up until then. A guide for the creation of the PSGroove is available through several online sources. George Hotz, better known under his nickname "geohot", appeared on Attack of the Show because he released the PlayStation 3's encryption keys, therefore any homebrew or custom firmware can be signed. Once signed, homebrew can be natively run. It would be difficult for Sony to fix this