The current eval kits come with Timesys linux for the A5 and Freescale's OS for the M4 part.
My application doesn't require Linux and I certainly like to avoid designing an external memory for the Linux. Instead I like to use FreeRtos for the A5 and bare metal code for the M4.
Has there been a port of FreeRtos for the A5?
Here are a couple of pages to help - the one to follow depends on the interrupt controller used in the Vybrid:
There are a number of Cortex-A5 and Cortex-A9 demos (basically the same port) in the FreeRTOS download that can be used as a reference, although these are not actually running on a Vybrid so you would need to create your own project.