According to the man page, you can sort the following columns:
SORTING of task window
For compatibility, this top supports most of the former top sort keys. Since this is primarily a service to former top users,
these commands do not appear on any help screen.
command sorted field supported
A start time (non-display) No
M %MEM Yes
N PID Yes
P %CPU Yes
T TIME+ Yes
Before using any of the following sort provisions, top suggests that you temporarily turn on column highlighting using the ’x’
interactive command. That will help ensure that the actual sort environment matches your intent.
The following interactive commands will only be honored when the current sort field is visible. The sort field might not be visi-
1) there is insufficient Screen Width
2) the ’f’ interactive command turned it Off
Moves the sort column to the left unless the current sort field is the first field being displayed.
Moves the sort column to the right unless the current sort field is the last field being displayed.
The following interactive commands will always be honored whether or not the current sort field is visible.
´F´ or ´O´ :Select_Sort_Field
These keys display a separate screen where you can change which field is used as the sort column.
If a field is selected which was not previously being displayed, it will be forced On when you return to the top display.
However, depending upon your screen width and the order of your fields, this sort field may not be displayable.
This interactive command can be a convenient way to simply verify the current sort field, when running top with column high-
lighting turned Off.
Using this interactive command you can alternate between high-to-low and low-to-high sorts.
Note: Field sorting uses internal values, not those in column display. Thus, the TTY and WCHAN fields will violate strict ASCII
It's all in the man pages...