In ADuC7060/61 datasheet (Rev. D | Page 39 of 108) inTable 38 there are values of typical RMS noise for Auxiliary ADC.
Are these values for the ADC1 operating with buffers enabled or disabled, e.g. ADC1CON [3:2] BUF_BYPASS [1:0] =  full buffer on, OR  full buffer bypass, OR some other setting?
A related question: If ADC1 was operating with a buffer disabled on one of its inputs -- how much offset shift one may encounter when a buffer is switched in?