I have been doing some work with the TMSC5515 DSP chip and noticed in the process of configuring ADCs for potentiometer control that the chip supports 6 ADC channels (VIN[5:0]), but only has 4 pins that can perform the conversion (GPAIN[3:0]). I've noticed this on other embedded processors as well.
What is the point of doing this? If the chip is only capable of reading 4 values at a time, the extra ADC channels don't seem like they would serve any purpose.
Discription of ADC on TMSC5515: http://www.ti.com/lit/ug/sprufp1c/sprufp1c.pdf