SMP8634 / SMP8635 “Secure Media Processors” from Sigma Designs are used in our set-top-box and digital signage applications.
In order to develop for that platform, an SDK must be purchased directly from Sigma Designs. There are different version of the SDK, once is mainly compatible with EM862X MRUA SDK and the newer one DCCHD is not, but offer a few more features.
However, as for EM8620 series, the Linux kernel is open source so companies need to release the source if they modified it in their products.
For example, you could download the GPL source released by Netgem – http://www.netgem.com/en/supportLinux.php for both Linux and utilities used in their NetBox HD. This is only the GPL source for your reference, after that there are also sigma linux drivers (not released by sigma) and not GPL, and the MRUA/DCCHD package that needs to be purchased from Sigma Designs.
Contrary to EM8620 series platforms (EM8620L, EM8621L, EM8622L, EM8623L etc..) , SMP8630 series (SMP8634 & SMP8635) do have a MMU (Memory Management Unit) so you won’t experience all the (apparently) random crashes and kernel panic due to stack overflows, you’ll be able to use fork and dynamic libraries and won’t be bothered by memory fragmentation.
Even though Sigma Designs does not provide online support for their customer (This has to be done thru their FAE), this platform is quite widely used and their are quite a few website explaining how to customize (should we say hack?) diverse set-top-box on the market such as DivCo TViX M-6500Aat Binary Art or OpenTViX or Western Digital WD TV Live at http://wdtv.wetpaint.com/