Notice that the GIGABYTE GA-H55N-USB3 becomes a better CPU overclocking platform when Load Line Calibration is disabled? We investigate why, and show you how to maximise your overclocks with a simple modification, or two.
GIGABYTE’s GA-H55N-USB3 is probably the most often overclocked mini-ITX form factor mainboard around. We have also heard that with the GA-H55N-USB3, processor overclocking improves with “Load Line Calibration” disabled in the BIOS. This goes against the general “belief” that the processor Voltage Regulation Module (VRM) should hold the processor VCC within the tightest possible margins at high processor clocks.
For the purpose of loading the VRM to simulate high current draw experienced during overclocking, we dropped an Intel® Core™ i7-860 Processor (4-cores, 8-threads) into the socket of the GA-H55N-USB3 and measured the processor VCC under 100% processor load and no-load (idle) conditions.
When the processor voltage is manually adjusted to 1.2V in the BIOS – and Load Line Calibration disabled – the VCC measured 1049mV, dropping to 1043mV upon the processor reaching full-load. Things were a little different once Load Line Calibration was enabled: The VCC measured while idling in Windows now comes closer to the BIOS value at 1227mV, however, under full-load, VCC then rises to 1257mV.
When the GA-H55N-USB3 is used in conjunction with high core-count or overclocked processors, the ISL6334 buck controller will compensate for the increased ohmic losses within the VRM output filters so long as Load Line Calibration is enabled. This is a useful feature for most overclockers. However, at even higher clock speeds or processor core-count, the load line regulation applied by the BIOS may fall outside specifications. It is therefore be necessary to introduce some deliberate droop to prevent overshoots (that can lead to premature overcurrent trips) or undershoots in the VRM output.
Two simple modifications can be made to customise the VRM load line regulation to your needs. Before that, it would be good to check if your load is responding well to the built-in “Load Line Calibration” settings.
With your multimeter’s black probe hooked to the ground of the 12V VRM input socket, measure the VCC values from any of the three highlighted points shown above. Do a check with the processor idling and under full-load, with and without Load Line Calibration enabled in the BIOS.
If enabling Load Line Calibration causes the VCC to increase under 100% processor load, head on to the next page to perform the modifications.