Allied Telesis x530 Series Installation Manual page 66

Chapter 2: Virtual Chassis Stacking
66
In stacks of three or more switches the amount of inter-switch network
traffic might require a stacking trunk with greater bandwidth than that
provided by the default ports of:
x530-28GTXm, x530-28GSX, and x530-28GPXm ports 27/S1 and

28/S2
x530-52GTXm and x530-52GPXm ports 51/S1 and 52/S2

For such situations additional SFP+ ports can be used:
x530-28GTXm and x530-28GPXm, and x530-28GSX ports 25 and

26
x530-52GTXm and x530-52GPXm ports 49 and 50

Note
x530-10GHXm and x530-18GHXm do not have additional SFP+
ports