Zalman ZM600-HP 600 W Power Supply Review
By Gabriel Torres on September 19, 2008
Zalman ZM600-HP is a 600 W power supply featuring a big 120 mm fan, an internal heatsink with a heat-pipe and modular cabling system. This unit is internally identical to OCZ GameXstream 700 W (the only difference between the two is the use of a heatsink with a heat-pipe and a modular cabling system on Zalman's model. Let’s take an in-depth look at this power supply and see if it can really deliver 600 W or even 700 W.
ZM600-HP features high-efficiency and active PFC. According to Zalman this power supply has an efficiency up to 84% under 230 V, meaning less power loss – an 80% efficiency means that 80% of the power pulled from the power grid will be converted in power on the power supply outputs and only 20% will be wasted. This translates into less consumption from the power grid (as less power needs to be pulled in order to generate the same amount of power on its outputs), meaning lower electricity bills. Of course we will test to see the actual efficiency from this power supply under several different loads.
Active PFC (Power Factor Correction), on the other hand, provides a better usage of the power grid and allows this power supply to be comply with the European law, making Zalman able to sell it in that continent (you can read more about PFC on our Power Supply Tutorial). In Figure 1, you can see that this power supply doesn’t have an 110V/220V switch, feature available on power supplies with active PFC.
Zalman is making a terrific job by explaining on the product box what makes this power supply different from other high-end models internally, like the use of two rectifying bridges, the use of three transistors on its active PFC circuit and four rectifiers on the +12 V output and a heatsink with heat-pipe to cool down the secondary rectifiers. All that is true, as we will show later.
This power supply uses a very good cooling solution. Instead of having a fan on its back, its fan is located at the bottom of the unit, as you can see in Figure 1 (the power supply is upside down). A mesh replaced the back fan, as you can see. Since the fan used is bigger than fans usually used on power supply units, this unit is not only quieter than traditional power supplies, but also provides a better airflow.
In Figure 2, you can see this power supply modular cabling system, used by its peripheral cables. Modular cabling system is great to help the PC internal airflow and organization, as you only need to connect the cables you will really use, so no unused cables will be hanging inside the PC. On this figure you can see that the plastic sleeving used by the main motherboard cables comes from inside the power supply, which is something we always point out that manufacturers should do. On Figures 3 and 4 you can see the peripheral cables that come with this unit.
As you can see, the cables use a plastic sleeving that improves the PC internal airflow and helps cables to be more organized. All peripheral cables come with a Velcro strap, helping you to organize the cables inside your PC.
This power supply comes with six peripheral power cables: one 6/8-pin PCI Express auxiliary power cable, two peripheral power cables containing two standard peripheral power connectors and one floppy disk drive power connector each, one peripheral power cable containing three standard peripheral power connectors, two Serial ATA power cables containing three SATA power connectors each and one “Y” adapter for connecting fans to any standard peripheral power cable.
This fan power adapter is really interesting, as it provides two connectors, one connected to +12 V (full speed) and the other connected to +5 V (low speed). So you can easily change your fan speed.
Three cables come from inside the power supply, not using the modular cabling system: the main 20/24-pin motherboard power cable, one ATX12V/EPS12V power cable and one 6-pin auxiliary PCI Express power cable for your video card.
The main motherboard cable comes with a 20/24-pin connector, however this connector isn’t a single 24-pin connector with the option for removing the extra four pins in order to get a 20-pin connector; instead this power supply has a 20-pin power connector with a loose 4-pin power connector on the same cable, as you can see in Figure 5.
This power supply doesn’t have a separated EPS12V connector; instead it provides two ATX12V connectors that can be put together for form one EPS12V connector (see Figure 6).
The gauge of all main wires is 18 AWG, which is adequate for a power supply on the 600 W power range.
Even though Zalman paid to have its own UL number, this power supply is really manufactured by FSP. On the power supply label is written “Manufactured by SPI Electronics Co., Ltd.,” which is the legal name of FSP.
As mentioned, internally this power supply is identical to OCZ GameXstream 700 W, with this model from OCZ not having the heatsink with heat-pipe or the modular cabling system. OCZ StealthXstream 600 W also uses the same project as these two power supplies, but using rectifiers with lower current limits (i.e., “less powerful”) on its secondary. Thus the comparison between ZM600-HP and these two units from OCZ is inevitable.
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 inside and to compare this power supply to others.
In this page, we will have an overall look, while in the next page we will discuss in details the quality and rating of the components used.
We can point out several differences between this power supply and a low-end (a.k.a. “generic”) one: the construction quality of the printed circuit board (PCB); the use of more components on the transient filtering stage; the active PFC circuitry; the power rating of all components; the design; etcetera.
On Figures 8 and 9 you can compare Zalman ZM600-HP to OCZ GameXstream 700 W. You can see only four differences between the two: the color of the PCB, the use of a different heatsink design, the use of a voltage regulator integrated circuit on OCZ GameXstream 700 W for creating a minimum load on the +5 V rail and the modular cabling system (available only on Zalman ZM600-HP). On the next pages we will be checking whether the components used on both power supplies are the same or not.
The design of the heatsink used on the secondary is really interesting, using a copper heat-pipe. In Figure 10, you can see it better.
As we mentioned on other articles, 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 than that, usually removing the MOV, which is essential for cutting spikes coming from the power grid, and the first coil.
Even though this power supply from Zalman has more components than the necessary – one extra X capacitor, two extra Y capacitors, one extra coil and a ferrite bead on the main power cable –, it doesn’t have a MOV, which is a sin for a power supply from this category.
A very interesting feature from this power supply is that its fuse is inside a fireproof rubber protection. So this protection will prevent the spark produced on the minute the fuse is blown from setting the power supply on fire.
This section is identical to the one found on OCZ StealthXstream 600 W and GameXstream 700 W.
In the next page we will have a more detailed discussion about the components used in the ZM600-HP.
We were very curious to check what components were chosen for the power section of this power supply and also how they were set together, i.e., the design used. We were willing to see if the components could really deliver the power announced by Zalman.
From all the specs provided on the databook of each component, we are more interested on the maximum continuous current parameter, given in ampères or amps for short. To find the maximum theoretical power capacity of the component in watts we need just to use the formula P = V x I, where P is power in watts, V is the voltage in volts and I is the current in ampères.
We also need to know under which temperature the component manufacturer measured the component maximum current (this piece of information is also found on the component databook). The higher the temperature, the lower current semiconductors can deliver. Currents given at temperatures lower than 50° C are no good, as temperatures below that don’t reflect the power supply real working conditions.
Keep in mind that this doesn’t mean that the power supply will deliver the maximum current rated for each component as the maximum power the power supply can deliver depends on other components used – like the transformer, coils, the PCB layout, the wire gauge and even the width of the printed circuit board traces – not only on the specs of the main components we are going to analyze.
For a better understanding of what we are talking here, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses two GBU606 rectifying bridges in its primary stage, which can deliver up to 6 A each (rated at 100° C), so the total current the rectifying section of this power supply can handle is of 12 A. These are the same components used by OCZ StealthXstream 600 W. OCZ GameXstream 700 W uses two GBU605 bridges, which have these same specs. This stage is clearly overspec'ed: 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 active PFC circuit from this power supply uses three power MOSFET transistors (20N60C3 – the same one used by several other power supplies we have reviewed), just like OCZ StealthXstream 600 W and OCZ GameXstream 700 W. These three power supplies are the only units we’ve seen so far using such design. All other power supplies we’ve seen to date use only two transistors (except Enermax Galaxy 1000 W, which uses four transistors). Each 20N60C3 can handle up 300 A @ 25° C each in pulse mode (which is the case).
The active PFC transistors and the PFC diode are installed on the same heatsink.
On the switching section two FQPF18N50V2 power MOSFET transistors in two-transistor forward configuration are used, and each one has a maximum rated current of 72 A in pulsating mode, which is the mode used, as the PWM circuit feeds these transistors with a square waveform. Interesting to note that these are the same transistors used by OCZ StealthXstream 600 W, OCZ GameXstream 700 W and Corsair HX620W power supplies.
The two rectifying bridges are installed on the same heatsink used by the switching transistors.
The primary section from power supply is controlled by a CM6800 integrated circuit, which is an active PFC and PWM controller combo. It is located on a small printed circuit board shown in Figure 16.
The electrolytic capacitor from the active PFC circuit is rated at 85° C and manufactured by CapXon, a Taiwanese company.
Like OCZ StealthXstream 600 W and OCZ GameXstream 700 W this power supply uses eight Schottky rectifiers on its secondary. On Zalman ZM600-HP and OCZ GameXstream 700 W and they are all the same model: MBRP3045N. This is really unique, as usually power supplies use a different rectifier for each output. Four of them are used for the +12 V output, two of them are used for the +5 V output and two of them are used for the +3.3 V output – even though the +3.3 V output uses a separated rectifier, it is connected at the same transformer outputs as the +5 V line.
OCZ GameXstream 600 W uses four MBRP3045N and four MBR2045CT and this is the main difference between this power supply and the other two. The four MBR2045CT rectifiers are used to produce the +12 V output and they have a lower maximum current/power (20 A vs. 30 A). So the main difference between OCZ StealthXstream 600 W and the other two power supplies based on the same design is the +12 V output.
Each MBRP3045N rectifier can handle up to 15 A per diode or 30 A per device (rated at 100° C). 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 uses four 15 A diodes in parallel. This would give us a maximum theoretical current of 86 A or 1,029 W for the +12 V output.
The +5 V output uses two 15 A diodes in parallel. This would give us a maximum theoretical current of 43 A or 214 W for the +5 V output.
The +3.3 V output uses two 15 A diodes in parallel. This would give us a maximum theoretical current of 43 A or 141 W for the +3.3 V output.
The maximum current each line can really deliver will depend on other components, in particular the coil used.
As you can see, the rectifiers are clearly overspec'ed.
In Figure 19 you have a better picture of the heatsink used on the secondary.
There is a thermal sensor located under the secondary heatsink. You can see this thermal sensor in Figure 19 (we removed the secondary heatsink to take this picture).
This power supply uses Taiwanese electrolytic capacitors from Teapo and OST rated at 105° C on its secondary. This power supply uses exactly the same capacitors as OCZ GameXstream 700 W and OCZ StealthXstream 600 W.
In Figure 20, you can see ZM600-HP label stating all its power specs.
As you can see, this power supply has four +12 V virtual rails, distributed like this:
This power distribution is perfect.
Now let’s see if this power supply can really deliver 600 W.
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
We tested this power supply under five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under 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 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.
+12V2 is the second +12V input from our load tester and during our tests it was connected to the power supply EPS12V connector, which is the only thing connected to the unit’s +12V1 rail. +12V1 is the first +12V input from our load tester and we connected the video card auxiliary power cable, the peripheral power cables and the main motherboard cable to it, so it was connected to +12V3 and +12V4 rails from the power supply.
We tried to use the same load pattern we used to test other 600 W units for a better comparison of the achieved results. We, however, had to use a different configuration for the test number 5 (100% load) because the power supply wouldn’t turn on if we configured the +12V2 input from our load tester (which was in fact connected to the power supply +12V1 rail) to pull 21.5 A like we did with other units. Since on the label was saying that each rail had a 16 A limit, this means that over current protection (OCP) was kicking in – which is great, by the way. So we had to reduce the current on +12V2 input and increase it on +12V1, which lead to a different configuration compared to tests we’ve done with other units on the 600 W range.
4 A (48 W)
9 A (108 W)
13 A (156 W)
17.5 A (210 W)
25.5 (306 W)
4 A (48 W)
9 A (108 W)
13 A (156 W)
17.5 A (210 W)
17.5 A (210 W)
1 A (5 W)
2 A (10 W)
4 A (20 W)
6 A (30 W)
8 A (40 W)
1 A (3.3 W)
2 A (6.6 W)
4 A (13.2 W)
6 A (19.8 W)
8 A (26.4 W)
1 A (5 W)
1 A (5 W)
1.5 A (7.5 W)
2 A (10 W)
2.5 A (12.5 W)
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)
% Max Load
Ripple and Noise
AC Power (1)
|AC Power (2)||143.9 W||293.3 W||434.1 W||597.1 W||753.0 W|
|AC Voltage||111.7 V||111.1 V||109.4 V||107.7 V||106.1 V|
Updated 06/24/2009: We re-tested this power supply using our new GWInstek GPM-8212 power meter, which is a precision instrument and provides accuracy of 0.2% and thus presenting the correct readings for AC power and efficiency (results marked as "2" on the table above; results marked as "1" were measured with our previous power meter from Brand Electronics, which isn't so precise as you can see). We also added the numbers for AC voltage during our tests, an important number as efficiency is directly proportional to AC voltage (the higher AC voltage is, the higher efficiency is). Also, manufacturers usually announce efficiency at 230 V, which usually inflates efficiency numbers. We added power factor (PF) numbers as well. These numbers measure the efficiency of the power supply active PFC circuit. This number should be as close to 1 as possible. Under light load (20% load, i.e., 120 W), the active PFC circuit from this unit isn't as good as when operating under higher loads, but 0.987 is an excellent number.
This power supply can really deliver 600 W of power at a room temperature of almost 49° C, which is great.
Zalman ZM600-HP achieves a very good efficiency if you pull between 40% and 60% from its labeled capacity (between 240 W and 360 W), around 84%. Under other loads efficiency is lower, but still above 80%.
Voltage stability was another highlight of this product, with all outputs between 3% of their nominal voltage in all tests, which is excellent (ATX standard allows voltages to be up to 5% from their nominal values and 10% in the case of the -12 V output). So voltages were always very close to their nominal values.
Noise level was also outstanding, far below the maximum allowed (120 mV peak-to-peak for 12 V outputs and 50 mV peak-to-peak for +5 V and +3.3 V outputs). Below you can see noise level for the test number five, when we were pulling 600 W from this unit.
Now let’s see if we could pull even more power from this unit and our tests of the power supply protections.
Before performing our overload tests we always like to test first if the over current protection (OCP) circuit is really active and at what level it is configured.
We configured +12V1 input from our load tester with a low current (1 A) and increased current on +12V2 input (which was connected to the power supply +12V1 rail) until the power supply shut down. This happened when we tried to pull more than 18 A, which is great, meaning that OCP is really active and only 2 A above what is printed on the label (16 A).
The maximum amount of power we could pull from Zalman ZM600-HP with it still working inside ATX specs can be found below. Even at this extreme configuration noise level was still halfway the maximum allowed, peaking 60 mV at +12V2 and 24.4 mV at +5 V.
33 A (396 W)
18 A (216 W)
13 A (65 W)
13 A (42.9 W)
2.5 A (12.5 W)
0.5 A (6 W)
% Max Load
Ripple and Noise
AC Power (1)
AC Power (2)
|AC Voltage||104.2 V|
Under this configuration efficiency dropped below 80% (consider the results marked as "2", as they are the correct ones, measured with our precision power meter).
Above this configuration the power supply would not turn on, showing its protections in action. So you don’t need to be afraid, this unit won’t die or explode if you pull more than it can handle.Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.
Zalman ZM600-HP power supply specs include:
* Researched at Shopping.com on the day we published this review.
Zalman ZM600-HP presents efficiency around 84% when you pull between 40% and 60% from its maximum capacity (between 240 W and 360 W). Under other load patterns efficiency was between 80% and 82%.
The noise level from power supply is impressively low and when we went to the extreme of pulling 740 W from it noise level was still only at half the maximum admissible.
It is a good product if you are looking for a power supply on the 600 W range with a modular cabling system.