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[nextpage title=”Introduction”]

Silent Pro M is a power supply series from Cooler Master featuring a modular cabling system and a single +12 V rail, at this moment featuring 500 W, 600 W, 700 W, 850 W and 1,000 W models. The  first three models have only the standard 80 Plus certification, while the 850 W and 1,000 W model have the 80 Plus Bronze certification, showing that they are based on a different design. Let’s see if the 600 W model (a.k.a. RS-600-AMBA-D3) is a good buy.

By the way, we have already reviewed the 850 W version from this series.

Cooler Master Silent Pro M 600 W power supplyFigure 1: Cooler Master Silent Pro M 600 W power supply.

Cooler Master Silent Pro M 600 W power supplyFigure 2: Cooler Master Silent Pro M 600 W power supply.

Cooler Master Silent Pro M 600 W is 5 7/8” (15 cm) deep, using a 135 mm fan on its bottom and featuring active PFC circuit, of course.

The modular cabling system present on the 600 W model has six connectors, two gray for the video card cables and four black for the SATA and peripheral power cables. The main motherboard cable and the ATX12V/EPS12V cable are permanently attached to the power supply. Both have a nylon protection that comes from inside the unit. The cables included are:

  • Main motherboard cable with a 20/24-pin connector, 18 ½” (47 cm) long (permanently attached to the power supply).
  • One cable with two ATX12V connectors that together form one EPS12V connector, 22” (56 cm) long (permanently attached to the power supply).
  • Two cables with one six/eight-pin connector for video cards each, 18 1/8” (46 cm) long.
  • Three cables with three SATA power connectors each, 17 ¾” (45 cm) to the first connector, 5 7/8” (15 cm) between connectors.
  • One cable with three standard peripheral power connectors, 18 1/8” (46 cm) to the first connector, 5 7/8” (15 cm) between connectors.
  • One cable with two standard power connectors and one floppy disk drive power connector, 18 1/8” (46 cm) to the first connector, 5 7/8” (15 cm) between connectors.

This configuration is perfect for a 600 W product. If you pay attention, this unit comes with a total of three SATA and two peripheral power cables, and the modular cabling system only allows the installation of four of these cables at the same time. This gives the user the flexibility to choose between having more SATA power cables or more peripheral power cables, depending on his or her particular configuration.

All cables use 18 AWG wires, which is the minimum recommended, and the cables from the modular cabling system are flat.

Cooler Master Silent Pro M 600 W power supplyFigure 3: Cables.

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

[nextpage title=”A Look Inside The Cooler Master Silent Pro M 600 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.

Cooler Master Silent Pro M 600 W power supplyFigure 4: Overall look.

Cooler Master Silent Pro M 600 W power supplyFigure 5: Overall look.

Cooler Master Silent Pro M 600 W power supplyFigure 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), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil. 

This power supply is flawless on this stage, with two Y capacitors and two X capacitors more than the minimum required, plus an X capacitor after the rectifying bridge.

Cooler Master Silent Pro M 600 W power supplyFigure 7: Transient filtering stage (part 1).

Cooler Master Silent Pro M 600 W power supplyFigure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion about the components used in the Cooler Master Silent Pro M 600 W.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of Cooler Master Silent Pro M 600 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one BU1506 rectifying bridge, which supports up to 15 A at 85° C if a heatsink is used (which is the case) or only up to 3.4 A at 25° C if it is not installed to a heatsink. At 115 V this unit would be able to pull up to 1,725 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 W without burning itself out. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

Cooler Master Silent Pro M 600 W power supplyFigure 9: Rectifying bridge.

Two STW20NM50 power MOSFET transistors are used on the active PFC circuit, each one capable of delivering up to 20 A at 25° C or up to 12.6 A at 100° C in continuous mode (note the difference temperature makes), or up to 80 A at 25° C in pulse mode, presenting an RDS(on) of 250 mΩ (resistance when the transistor is turned on; the lower this number the better, meaning higher efficiency).

This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor, manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board, as two or more capacitors with small capacitance are physically smaller than one capacitor with the same total capacitance. Cooler Master Silent Pro M 600 W uses two 270 µF x 420 V capacitors in parallel; this is equivalent of one 540 µF x 420 V capacitor. These capacitors are Japanese, from Matsushita and labeled at 85° C.

The reviewed power supply uses two STP20NM50FD power MOSFET transistors on its switching section, installed on the traditional two-transistor forward configuration. Each transistor can handle up to 20 A at 25° C or up to 14 A at 100° C in continuous mode, or up to 80 A at 25° C in pulse mode, with a maximum RDS(on) of 250 mΩ.

Cooler Master Silent Pro M 600 W power supplyFigure 10: Switching transistors, active PFC diode and active PFC transistors.

The primary is controlled by a CM6806 PFC/PWM combo controller.

Cooler Master Silent Pro M 600 W power supplyFigure 11: PFC/PWM combo controller.

Now let’s take a look at the secondary of this power supply.

[nextpage title=”Secondary Analysis”]

This power supply has five Schottky rectifiers on its secondary.

The maximum theoretical current each 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. Just as an exercise, we can assume a typical duty cycle of 30%.

The +12 V output is produced by three 40CPQ060 Schottky rectifiers, each one supporting up to 40 A (20 A per internal diode at 120° C, 0.49 V maximum voltage drop). Two of them are used for the “freewheeling” part of the rectification, while one use used for the direct rectification part. This way we have a maximum theoretical current of 57 A or 686 W for the +12 V output.

The +5 V output is produced by one STPS60L45CW Schottky rectifier, which is capable of delivering up to 60 A (30 A per internal diode at 135° C, 0.50 V maximum voltage drop), giving us a maximum theoretical current of 43 A or 214 W for the +5 V output.

The +3.3 V output is produced by another STPS60L45CW Schottky rectifier, giving us a maximum theoretical current of 43 A or 141 W for the +3.3 V output.

All these numbers are theoretical. The real amount of current/power each output can deliver is limited by other components, especially by the coils used on each output.

Cooler Master Silent Pro M 600 W power supplyFigure 12: +3.3 V, +5 V and +12 V rectifiers.

The outputs are monitored by a PS223 integrated circuit, which supports over voltage (OVP), under voltage (UVP), over current (OCP) and over temperature (OTP) protections. Over temperature protection is really enabled, since we could clearly see two thermal sensors on the secondary heatsink (power supplies with this protection usually need two sensors, one for controlling the speed of the fan and another for controlling the over temperature protection).

Cooler Master Silent Pro M 600 W power supplyFigure 13: Monitoring integrated circuit.

But what is unique about this unit is the presence of an additional protection circuit on the modular cabling system (see Figure 14), controlled by an LM339 voltage comparator.

Cooler Master Silent Pro M 600 W power supplyFigure 14: Monitoring circuit on the modular cabling system.

All capacitors from the secondary are from Teapo.

[nextpage title=”Power Distribution”]

In Figure 15, you can see the power supply label containing all the power specs.

Cooler Master Silent Pro M 600 W power supplyFigure 15: Power supply label.

As you can see, this power supply uses a single-rail design on the +12 V output, so there is not much to talk about here.

Now let’s see if this power supply can really deliver 600 W.

[nextpage title=”Load Tests”]

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

First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.

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 ou
tput 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.

The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test both inputs were connected to the power supply single rail (+12VB input was connected to the power supply EPS12V connector from the cable that is permanently attached to the power supply and all other cables were connected to the load tester +12VA input).

Input Test 1 Test 2 Test 3 Test 4 Test 5
+12VA 4 A (48 W) 9 A (108 W) 13 A (156 W) 17.5 A (210 W) 21.5 A (258 W)
+12VB 4 A (48 W) 9 A (108 W) 13 A (156 W) 17.5 A (210 W) 21.5 A (258 W)
+5V 1 A (5 W) 2 A (10 W) 4 A (20 W) 6 A (30 W) 8 A (40 W)
+3.3 V 1 A (5 W) 2 A (6.6 W) 4 A (13.2 W) 6 A (19.8 W) 8 A (26.4 W)
+5VSB 1 A (5 W) 1 A (5 W) 1.5 A (7.5 W) 2 A (10 W) 3 A (15 W)
-12 V 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W)
Total 114.9 W 242.2 W 356.1 W 479.7 W 592.4 W
% Max Load 19.2% 40.4% 59.4% 80.0% 98.7%
Room Temp. 43.8° C 43.4° C 44.9° C 47.4° C 47.6° C
PSU Temp. 42.1° C 42.1° C 45.2° C 47.3° C 50.5° C
Voltage Regulation Pass Pass Pass Pass Pass
Ripple and Noise Pass Pass Pass Pass Pass
AC Power 134.4 W 279.7 W 417.2 W 575.0 W 731.0 W
Efficiency 85.5% 86.6% 85.4% 83.4% 81.0%
AC Voltage 116.2 V 114.9 V 113.5 V 111.6 V 109.2 V
Power Factor 0.964 0.988 0.993 0.995 0.995
Final Result Pass Pass Pass Pass Pass

Cooler Master Silent Pro M 600 W can really deliver its labeled power at high temperatures.

We were actually surprised with its performance. Since it has “only” the standard 80 Plus certification, we were expecting to see a unit with 80-82% efficiency across the board, but we are happy to be wrong: Cooler Master Silent Pro M 600 W could achieve a high efficiency between 85.5% and 86.6% when we pulled up to 360 W. Pulling 480 W from it efficiency was still high at 83.4%. And at full load (600 W) efficiency was at 81%.

Voltage regulation was excellent, with all voltages within 3% from their nominal values (except -12 V during all tests one and two) – i.e., values closer to their “face value” than required, as the ATX12V specification allows voltages to be within 5% from their nominal values (10% for -12 V).

And then we have noise and ripple, which were very low. Below you can see the results during test five. The maximum allowed is 120 mV on +12 V and 50 mV on +5 V and +3.3 V. All these numbers are peak-to-peak figures.

Cooler Master Silent Pro M 600 W power supplyFigure 16: +12VA input from load tester at 592.4 W (55.6 mV).

Cooler Master Silent Pro M 600 W power supplyFigure 17: +12VB input from load tester at 592.4 W (47.6 mV).

Cooler Master Silent Pro M 600 W power supplyFigure 18: +5 V rail with power supply delivering 592.4 W (15.6 mV).

Cooler Master Silent Pro M 600 W power supplyFigure 19: +3.3 V rail with power supply delivering 592.4 W (9.2 mV).

Let’s see if we can pull more power from this unit.

[nextpage title=”Overload Tests”]

Below you can see the maximum we could pull from this unit. If we increased one amp on any given output the unit would shut down, which is terrific. It seems that its over current protection (OCP) on +12 V rail is set at 50 A.

Input Overload Test
+12VA 25 A (300 W)
+12VB 24 A (288 W)
+5V 10 A (50 W)
+3.3 V 10 A (33 W)
+5VSB 3 A (15 W)
-12 V 0.5 A (6 W)
Total 678.9 W
% Max Load 113.2%
Room Temp. 36.1° C
PSU Temp. 42.4° C
AC Power 853.0 W
Efficiency 79.6%
AC Voltage 108.7 V
Power Factor 0.996

[nextpage title=”Main Specifications”]

Cooler Master Silent Pro M 600 W power supply specs include:

  • ATX12V 2.3
  • EPS12V 2.91
  • Nominal labeled power: 600 W.
  • Measured maximum power: 678.9 W at 36.1° C.
  • Labeled efficiency: 85% at typical load (i.e., at 300 W), 80 Plus Standard certification
  • Measured efficiency: Between 81.0% and 86.6% at 115 V (nominal, see complete results for actual voltage).
  • Active PFC: Yes.
  • Modular Cabling System: Yes, partial.
  • Motherboard Power Connectors: One 20/24-pin connector and two ATX12V connectors that together form an EPS12V connector (both permanently attached to the power supply).
  • Video Card Power Connectors: Two six/eight-pin connectors in separated cables (modular cabling system).
  • SATA Power Connectors: Nine in three cables (modular cabling system).
  • Peripheral Power Connectors: Five in two cables (modular cabling system).
  • Floppy Disk Drive Power Connectors: One.
  • Protections: Over Voltage (OVP), Under Voltage (UVP), Over Current (OCP, tested and working), Over Power (OPP), Over Temperature (OTP) and Short-Circuit (SCP, tested and working).
  • Warranty: Five years.
  • More Information: https://www.coolermaster-usa.com
  • Average price in the US*: USD 100.00.

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

[nex
tpage title=”Conclusions”]

We were really surprised with this power supply. Since it “only” has the standard 80 Plus certification, we were expecting it to achieve, in the best case scenario, efficiency between 80-82%. And since the latest power supply from Cooler Master with standard 80 Plus certification we tested, GX 750 W, proved to be a true “bomb” with efficiency below 80% and noise and ripple above the maximum allowed, to be honest we were not expecting much from Silent Pro M 600 W.

We are happy to be wrong! It delivered high efficiency between 83.4% and 86.6% most of the time (at full load efficiency was at 81.0%), the main voltages were always within 3% of their nominal values (ATX12V specification allows them to be up to 5% distant, so this mean that voltages were closer to their nominal values than required) and noise and ripple was always low. Sweet!

Then we have pricing. It is being sold for USD 100 in the United States, which puts it as a no-brainer against its main competitors, like Zalman ZM600-HP (USD 124 and lower efficiency) and Zalman ZM600-RS (comparable performance but costing USD 115). Of course it presents a far better performance (especially on efficiency) than more inexpensive products – in fact it is cheaper and a way better product than Cooler Master GX 750 W.

As one final note, the manufacturer website says that this unit has “Japanese capacitors.” Several manufacturers are with this problem on putting on plural when only the capacitors from the primary are Japanese. They should change this phrase to “Japanese capacitors on primary” or similar wording to avoid users thinking that all capacitors are made in Japan, which is not the case.