It turns out when Skype limited 10 way calling to Intel Processors only it really was arbitrary! Maxxus has a patched version of Skype (download SkypeSetup 2.0.0.90 + patched executable) that allows 10-way calling regardless of the processor installed.

Recently, Skype and Intel have announced a deal that would limit Skype's functionality on all but specific Intel processors. Currently, Skype 2.0 offers 10-way conference calls only on Intel's latest dual-core CPUs, while other chips, including all AMD chips, will only allow for 5-way conference calls. It is argued that only those Intel dual-core CPUs meet the requirements - which would imply that no AMD CPU is fast enough.

The patch is the result of two phases: code analysis and design of the patch. The code analysis, or reverse engineering, reveals the relevant code block, which overrides Skype's limitation for Intel's dual-core CPUs. The patch design isolates the minimal set of instructions that need to be modified to cancel this limitation.