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[nextpage title=”Introduction”]

Cooler Master eXtreme Power Plus is a 500 W power supply that is being sold for only USD 40 at Newegg.com (USD 30 after a USD 10 mail-in rebate). Can it really deliver its labeled power? Let’s see if this unit survives our tests.

We have already reviewed the 460 W model from this same series, which was not able to deliver its labeled power. So we were really curious about the 500 W version from this power supply.

You need to pay attention as Cooler Master has two power supply series with similar names. The eXtreme Power series is around for a while and the power supplies from this series are presumably manufactured by Seventeam. Units from eXtreme Power Plus are manufactured by AcBel Polytech. So even though the names of these series are similar, each series use a different internal design.

The reviewed model is also called RS-500-PCAR-A3. Two things immediately caught our attention. First, the fact there is no reference for “500 W” on the power supply. If you pay close attention to the label (Figures 1 and 13) you will see that the number “500” printed on the upper right corner doesn’t have the letter “W” after it. This is usually a trick done by manufacturers to protect themselves against potential lawsuits (e.g., “we didn’t say this was a 500 W power supply; 500 is the model number;” a good example is the AcBel iPower 660 power supply we reviewed, which isn’t a 660 W model – hey, wait a minute… eXtreme Power Plus 500 W is also manufactured by AcBel… Hum…)

The second thing that we noticed on the label was the phrase “The +3.3 V & + 5 V & +12V1 & +12V2 combine power shall not exceed 431.5 W.” What? If you add this to the maximum power for -12 V and +5VSB we have a total of 450 W! So despite the product name, the label states in a format hard to be understood by the average user that this is in fact a 450 W power supply. As you know, we are completely against this kind of trick used by some manufacturers, and we honestly think that companies like this should be sued, as they are clearly trying to induce consumers to error. Nevertheless, for now we have to give Cooler Master the benefit of the doubt; let’s see during our load tests what is the real maximum power this unit can deliver.

Cooler Master eXtreme Power Plus 500 WFigure 1: Cooler Master eXtreme Power Plus 500 W (RS-500-PCAR-A3) power supply.

Cooler Master eXtreme Power Plus 500 WFigure 2: Cooler Master eXtreme Power Plus 500 W (RS-500-PCAR-A3) power supply.

Cooler Master eXtreme Power Plus 500 W is a small power supply (5 ½” or 14 cm deep) and doesn’t have active PFC.

The main motherboard cable uses a 20/24-pin connector, being the only one protected by a nylon sleeving that comes from inside the power supply housing. It comes with two ATX12V connectors that together form an EPS12V plug.

The reviewed power supply comes with only four peripheral cables: one with one six-pin auxiliary power connector for video cards, two with two SATA power connectors and one standard peripheral power plug and one with three standard peripheral power connectors and one floppy disk drive power connector.

Only the ATX12V/EPS12V cable uses wires with the correct gauge (18 AWG). All other cables use thinner 20 AWG wires. The use of thinner wires usually make the voltage to drop at the power connectors when the power supply is fully loaded. This is where the manufacturer could cut some cost.

We could complain about the number of connectors available, but we think four SATA connectors is more than compatible with a USD 40 product. But for a 500 W product it could come with two cables for video cards instead of just one, but once again this is how the manufacturer was able to cut costs.

The distance between the power supply housing and the first connector on each cable is of 15 ¾” (40 cm), and the distance between each connector on cables that have more than one plug is of 4 ¾” (12 cm). The good exception is the ATX12V/EPS12V cable, which is 21 ¼” (54 cm) long.

Cooler Master eXtreme Power Plus 500 WFigure 3: Cables.

Now let’s take an in-depth look inside this power supply.

[nextpage title=”A Look Inside The eXtreme Power Plus 500 W”]

We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.

This page will be an overview, and then in the following pages we will discuss in detail the quality and ratings of the components used.

Here we could see several differences between this 500 W model and the 460 W model we have already reviewed, so at least they don’t use the same printed circuit board (but let’s see if the components are the same in the next pages).

Cooler Master eXtreme Power Plus 500 WFigure 4: Overall look.

Cooler Master eXtreme Power Plus 500 WFigure 5: Overall look.

Cooler Master eXtreme Power Plus 500 WFigure 6: Overall look.

[nextpage title=”Transient Filtering Stage”]

As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor, yellow component on the pictures below) and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.

At least here this power supply uses a good design, with two Y capacitors and one X capacitor more than needed. The MOV’s are placed between the two electrolytic capacitors from the voltage
doubler, as it is usual to be done on power supplies without active PFC.

Cooler Master eXtreme Power Plus 500 WFigure 7: Transient filtering stage (part 1).

Cooler Master eXtreme Power Plus 500 WFigure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion about the components used in the eXtreme Power Plus 500 W.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of eXtreme Power Plus 500 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU605 rectifying bridges connected in parallel in its primary. Each bridge can deliver up to 6 A (rated at 100° C), for a total of 12 A at 100° C. This stage is clearly overspec’ed, as power supplies from this power range usually use only one 6 A or 8 A bridge. At 115 V this unit would be able to pull up to 1,380 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,104 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply. The bridges don’t use a heatsink, which can lower the maximum current they can deliver.

Cooler Master eXtreme Power Plus 500 WFigure 9: Rectifying bridges.

On the switching section this power supply uses two 2SK2611 power MOSFET transistors in parallel in a single-transistor forward configuration. Most modern power supplies use a different configuration, two-transistor forward, which is more efficient. At least this power supply isn’t based on the half-bridge design using bipolar transistors, which is outdated. Each 2SK2611 can drive up to 9 A in continuous mode, or up to 27 A in pulse mode (which is the mode used), so the maximum current the switching section can drive is 18 A in continuous mode or 54 A in pulse mode. All values were measured at 25° C. Here eXtreme Power Plus 500 W is different from the 460 W model, which uses the same design but with transistors with lower current limits (7 A each).

Cooler Master eXtreme Power Plus 500 WFigure 10: Switching transistors.

The primary is controlled by a UC3843B PWM controller.

[nextpage title=”Secondary Analysis”]

This power supply has six Schottky rectifiers on its secondary, two for each positive voltage output (+12 V, +5 V and +3.3 V).

The +12 V output is produced by two STPS20S100CT Schottky rectifiers connected in parallel, each one supporting up to 20 A at 150° C (10 A per internal diode). The maximum theoretical current the +12 V line can deliver is given by the formula I / (1 – D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by two 10 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 29 A or 343 W for the +12 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used. The 460 W model uses different rectifiers here, but with the exact same current limits.

The +5 V output is produced by two MBR2045CT Schottky rectifiers in parallel, supporting up to 20 A at 165° C (10 A per internal diode) each. Using the same math we have a maximum theoretical current of 29 A or 143 W for the +5 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used. The 460 W model uses similar devices.

The +3.3 V output is produced by another two MBR2045 Schottky rectifiers in parallel, supporting up to 20 A at 165° C (10 A per internal diode) each. So the maximum theoretical current the +3.3 V output can deliver is of 29 A or 94 W, using the same math described above. As mentioned the real power this line can deliver depends on other factors. The 460 W model uses similar devices.

On this power supply the -12 V is regulated using a 7912 integrated circuit.

So, in summary, the secondary from both 460 W and 500 W models is identical.

Cooler Master eXtreme Power Plus 500 WFigure 11: +12 V, +5 V and +3.3 V rectifiers.

This power supply uses a WT7527 monitoring integrated circuit, which is in charge of the power supply protections. It supports over voltage (OVP), under voltage (UVP) and over current (OCP) protections. OCP was really activated, as we will talk about later.

Cooler Master eXtreme Power Plus 500 WFigure 12: Monitoring integrated circuit.

The electrolytic capacitors from the voltage doubler are from Elite (a Thai company) and the capacitors from the secondary are from Ltec (a Taiwanese company).[nextpage title=”Power Distribution”]

In Figure 13, you can see the power supply label containing all the power specs.

Cooler Master eXtreme Power Plus 500 WFigure 13: Power supply label.

As you can see this power supply has two +12 V rails, which are distributed like this:

  • +12V1 (yellow with black stripe wire): Main motherboard cable, peripheral power connectors, SATA power connectors and video card power connector.
  • +12V2 (solid yellow wire): ATX12V/EPS12V connector.

The rails are well-distributed, as the CPU (ATX12V/EPS12V) and video card are on different rails.

Now let’s see if this power supply can really deliver 500 W.[nextpage
title=”Load Tests”]

We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.

As you are probably already familiar, we test power supplies with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity. However, since we were suspecting that this would be a 450 W unit, we added a load pattern for this power range (which is equivalent of around 90% of 500 W), respecting the 360 W limit for the +12 V outputs that was posted on the label (test number five).

Then for the 100% load test we used two patterns, one respecting this 360 W limit (test number six), which made us to pull more power from +5 V and +3.3 V than we wanted to, and another not respecting it (test number seven), pulling more power from +12 V, since this is the way we usually test power supplies, as nowadays most power is concentrated on the +12 V rails as the CPU and the video card are connected to them.

If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.

+12V1 and +12V2 are the two independent +12V inputs from our load tester and during our tests the +12V1 input was connected to the power supply +12V1 (main motherboard connector and peripheral power connectors) while the +12V2 input was connected to the power supply +12V2 rail (EPS12V connector).

Input Test 1 Test 2 Test 3 Test 4
+12V1 4 A (48 W) 7 A (84 W) 11 A (132 W) 14.5 A (174 W)
+12V2 3 A (36 W) 7 A (84 W) 10 A (120 W) 14 A (168 W)
+5V 1 A (5 W) 2 A (10 W) 4 A (20 W) 5 A (25 W)
+3.3 V 1 A (3.3 W) 2 A (6.6 W) 4 A (13.2 W) 5 A (16.5 W)
+5VSB 1 A (5 W) 1 A (5 W) 1.5 A (7.5 W) 2 A (10 W)
-12 V 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W)
Total 102.9 W 194.3 W 295.0 W 392.0 W
% Max Load 20.6% 38.9% 59.0% 78.4%
Room Temp. 48.4° C 48.3° C 47.1° C 48.8° C
PSU Temp. 50.2° C 50.1° C 48.9° C 52.3° C
Voltage Stability Pass Pass Pass Pass
Ripple and Noise Pass Pass Pass Fail
AC Power 132 W 239 W 366 W 503 W
Efficiency 78.0% 81.3% 80.6% 77.9%
Final Result Pass Pass Pass Fail
Input Test 5 Test 6 Test 7
+12V1 15 A (180 W) 15 A (180 W) 18 A (216 W)
+12V2 15 A (180 W) 15 A (180 W) 18 A (216 W)
+5V 9 A (45 W) 15 A (75 W) 6 A (30 W)
+3.3 V 9 A (29.7 W) 15 A (49.5 W) 6 A (19.8 W)
+5VSB 2.5 A (12.5 W) 2.5 A (12.5 W) 2.5 A (12.5 W)
-12 V 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W)
Total 446.9 W 499.9 W 485.5 W
% Max Load 89.4% 100.0% 97.1%
Room Temp. 46.8° C 47.4° C 50.9° C
PSU Temp. 54.1° C 50.6° C 55.1° C
Voltage Stability Pass Pass Pass
Ripple and Noise Fail Fail Fail
AC Power 588 W 681 W 659 W
Efficiency 76.0% 73.4% 73.7%
Final Result Fail Fail Fail

Cooler Master eXtreme 500 W could deliver 500 W, however power isn’t everything. Efficiency was above 80% only when we pulled between 40% and 60% (200 W – 300 W) from the power supply nominal maximum power, and when we pulled its full power efficiency was at the 73% range, which is really bad.

But the real problem with this power supply is its ripple and noise level. When we pulled 60% of the power supply maximum power noise level at +12V1 and +12V2 was at 104.4 mV and 98.9 mV, respectively. Very high, but still within the 120 mV set by ATX specs. But from 80% load on ripple and noise level was always above specs: 128.6 mV and 122.2 mV during test number four, 130.2 mV and 125.6 mV during test number five, 172.6 mV and 167.4 mV during test number six and 149.6 mV and 145.4 mV during test number seven. These numbers are for +12V1 and +12V2 rails, respectively, and are peak-to-peak figures.

Noise level at +3.3 V was always below 20.4 mV, which is good, but +5 V output reached 49.2 mV during test number six, hitting the 50 mV limit for this output.

Below you see the images for ripple and noise during test number seven.

Cooler Master eXtreme Power Plus 500 WFigure 14: Noise level at +12V1 input from our load tester with the reviewed unit delivering 485.5 W (149.6 mV).

Cooler Master eXtreme Power Plus 500 WFigure 15: Noise level at +12V2 input from our load tester with the reviewed unit delivering 485.5 W (145.4 mV).

Cooler Master eXtreme Power Plus 500 WFigure 16: Noise level at +5 V input from our load tester with the reviewed unit delivering 485.5 W (42.4 mV).

Cooler Master eXtreme Power Plus 500 WFigure 17: Noise level at +3.3 V input from our load tester with the reviewed unit delivering 485.5 W (20.4 mV).

[nextpage title=”Load Tests (Cont’d)”]

We always try to pull more power from the units we review. But in order to consider an overload successful, the outputs must be with noise and ripple within the range declared on ATX specs. Since this power supply was already with noise and ripple outside specs during normal range of operation, we decided to not overload it.

We, however, tested its the over current protection (OCP) circuit, to see if it is active and at what level it is config
ured.

In order to do that we configured +12V1 with a very low current (1 A) and increased current on +12V2 until we couldn’t turn on the power supply. This happened when we tried to pull more than 24 A from it. So the OCP circuit is configured at 24 A, while the label says each rail can deliver up to 18 A. OCP configuration could be tighter, but we’ve seen lots of power supplies with OCP configured with values way above that.

[nextpage title=”Main Specifications”]

Cooler Master eXtreme Power Plus 500 W power supply specs include:

  • ATX12V 2.3
  • Nominal labeled power: 500 W.
  • Measured maximum power: 499.9 W at 47.4° C.
  • Labeled efficiency: 70% minimum.
  • Measured efficiency: Between 73.4% and 81.3%.
  • Active PFC: No.
  • Modular Cabling System: No.
  • Motherboard Power Connectors: One 24-pin connector and two ATX12V connectors that together form an EPS12V connector.
  • Video Card Power Connectors: One six-pin connector.
  • Peripheral Power Connectors: Five in three cables.
  • Floppy Disk Drive Power Connectors: One.
  • SATA Power Connectors: Four in two cables.
  • Protections: Over current (OCP, tested and working), over voltage (OVP, not tested), over power (OPP, not tested) and short-circuit (SCP, tested and working).
  • Warranty: Two years.
  • More Information: https://www.coolermaster-usa.com
  • Real manufacturer: AcBel Polytech
  • Average price in the US*: USD 40.00.

* Researched at Newegg.com on the day we published this review.

[nextpage title=”Conclusions”]

Cooler Master eXtreme Power Plus 500 W is the perfect example to explain why maximum power isn’t everything. This power supply can really deliver 500 W, but with efficiency above 80% only when you pull between 40% and 60% load (between 200 W and 300 W) and electrical noise level above the maximum allowed if you pull 80% load or more (i.e., starting at 400 W).

On the other hand, we have pricing. At USD 40 (or USD 30 if you buy at Newegg.com and don’t forget to fill-out the USD 10 mail-in rebate form), it is probably one of the cheapest “real” 500 W power supplies around.

On the good side, we have a good number of SATA and peripheral power connectors for a low-end product.

We can’t recommend this power supply, however if you are really on a budget this may be an option until you have money to buy a decent power supply for your PC.

Compared to the 460 W model we have already reviewed, the main components are the same, with the switching transistors replaced with more powerful models. The printed circuit board, however, is different.