QADC doubt

We have some doubts on ADC modules in MPC565. 

It consists of 40 channel and two ADC modules viz QADC A and B. We are 
developing low level driver for this module in C.

In reference manual Chapter 13, QADC is described as follows 

The two queued analog-to-digital converter (QADC) modules on the MPC565 
are 10-bit, unipolar, successive approximation converters with analog 
multiplexers. These modules are configured so each module can access 
all 40 of the part's analog inputs.

What is the need for having two modules separately with access to same 
channels? 

When we are writing drivers we are not sure how to use both the modules.

Please advice.