According to the xclock man page, under options, at '-render', it claims using Xrender is default when xclock is compiled with Xrender support.
However; running xclock without arguments looks the same as when ran with the -norender option. Running xclock with the -render gives smooth clock hands, so it seems reasonable to me to assume Xrender support is built in and works. This is tested on my laptop with a -current snapshot from 07/07. The video card is an Intel GM965 builtin (8086 2a03).
