Articles :: Modular Power Supplies: The Reality of the Resistance. ::

Jon Gerow · 08-10-2006 · Category: Guides


Modular power supplies have become very popular as of late. A modular power supply is different from a typical PC power supply in that it has cables that can be plugged in as the user needs them. By giving the user the ability to only have the cables they need plugged into the power supply, with no additional, unused cables, the user can have less clutter inside their computer case, and as a bonus, have improved air-flow.

Some companies have refused to manufacture modular power supplies and have even taken the effort to spread fud (fear, uncertainty and doubt) over the very concept of modular power supply connectors.

The argument? The resistance of the modular interface reduces the performance of the power supply, because resistance causes voltages to drop. No doubt any modular connection causes resistance. Nobody's denying that. But how much does the resistance of the modular connectors effect the voltage delivered to your peripherals?

To find this out, we're going to use a power supply load tester to put a static load on a number of power supplies: both modular and non-modular. We're going to apply different loads (from no load to 11A) to a particular connector on the power supplies (the PCI-e six pin seems like a good choice), and then use a DMM (digital multi-meter) to measure the voltages.

The voltages will be measured at four different points when testing the modular power supplies. First, the voltage will be measured at the point where the wire from the power supply's main circuit board (main PCB) meets the modular interfaces circuit board (modular PCB.) Second, voltages will be measured at the modular connector, where one would plug the modular cable into the power supply. Third, voltages will be measured at the connector and the load. Fourth and finally, voltage will be measured at the load itself, at the very end of the connector where you would have your motherboard, peripheral, video card, etc. plugged in.

The standard, non-modular power supplies will have their voltages measured at three points. The main PCB, the connector at the load and at the load.

The first thing I want to do is show you my DMM. A good DMM is important for any computer technician. And once you have a good DMM, you'll find yourself using it for everything! Automotive, household, etc.

Mine is a Uni-Trend UT204. I bought it when I was over in Taiwan. It's very accurate at 0.8% and has an excellent resolution (measures as low as 0.1mV).

Since I'm going to need two places to the left of the decimal point, my readings are only going to be 10mV accurate (.01V.)


  1. Introduction
  2. Testing Methodology / Testing Corsair HX620W
  3. Testing Corsair HX620W (continued)
  4. Testing Corsair HX620W (results)
  5. Testing Ultra X2 550W
  6. Testing Antec NeoHE 430W
  7. Testing Fortron Source FSP600-80GLC
  8. Testing Silverstone ST65ZF
  9. Charting voltage output results for all five load tests
  10. Side by side comparison charts of voltage output
  11. Conclusion

Discuss This Article