Sorry, read the text, not the title.

From the manual
Count Pulse
0 0 0 Internal clock, fOSC/6 in 6-clock mode (fOSC/12 in 12-clock mode)
0 1 1 Internal clock, fOSC/2 in 6-clock mode (fOSC/4 in 12-clock mode)
and
The frequency of the output depends on
the source for the PCA timer.

so the max freq should be Fosc/4

Erik