GRID's DOCELL statement allows you to find the coordinates of the maximum value in a floating point grid.
Run this aml from the GRID prompt:
/* USAGE: &RUN XYOFMAX.AML <input_grid>
z1 = scalar(%grd$zmin%)
if (%ingrd% > z1)
z1 := %ingrd%
xmap := scalar($$xmap)
ymap := scalar($$ymap)
&ty [show scalar xmap]
&ty [show scalar ymap]
Note: This is not an ESRI supported aml. Use at your own risk. Please make a backup of your data before running this aml and carefully check the output. This aml does no error checking and it is meant only as a guide to developing an aml specific to your data inputs and desired outputs.
There is no provision within this methodology to identify multiple occurrences of the maximum value.