...

RenderMan XPU can be considered another variant of RenderMan itself – a companion to RenderMan RIS.  All of the techniques you have learned about to use RenderMan RIS apply to using XPU.  The BxDFs and the patterns all are usable with RenderMan XPU.  The look that you get from RenderMan XPU will be predictive of RenderMan RIS.  It won't be pixel-for-pixel accurate.  But it will give you a render that is very close to what you will get from RIS. 

Take a look at the general documentation for the Shading BxDFs and Patterns to understand the possibilities you can achieve with RenderMan XPU and RIS.  While RenderMan XPU is predictive of RIS, take a look at the documentation for the differences between the two.  That documentation also covers what isn't yet supported in XPU.

...