OCZ GameXstream 700 W Power Supply
By Gabriel Torres on November 8, 2006
GameXstream 700 W (also known as OCZGXS700) is a high-end power supply belonging to OCZ’s latest series, GameXstream. This model features a big 120 mm fan and is EPS12V-compatible, being targeted to high-end SLI and CrossFire systems. Let’s take an in-depth look at this power supply.
Being a high-end power supply, GameXstream 700 W features high-efficiency and active PFC. According to OCZ this power supply has an efficiency up to 80% (or 83% under 230 V; compare to 50% to 60% on regular power supplies), 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.
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 OCZ 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.
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 the cables used by this power supply. As you can see, the cables use a plastic sleeving that improves the PC internal airflow and helps cables to be more organized. Another detail that shows the high finishing quality of this power supply is that the plastic sleeving come from inside the power supply housing, so no wire is exposed in their way out of the PSU housing.
This power supply comes with six peripheral power cables: two PCI Express auxiliary power cables; two peripheral power cables containing three standard peripheral power connectors and one floppy disk drive power connector each and two Serial ATA power cables containing three SATA power connectors each.
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 for you to have 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 3.
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.
The gauge of all main wires is 18 AWG but the +12 V (yellow) wires on the motherboard cables are 16 AWG, which is great.
We decided to fully disassemble this power supply to take a look inside.
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.
One thing caught our eye immediately as soon as we opened this power supply: the secondary heatsink is L-shaped using the power supply housing as a secondary heatsink. This is really interesting. Pay attention in Figure 5 to see this.
On Figures 6 and 7 you can have an overall look from inside this power supply.
Another feature that you can clearly see on the above pictures is a voltage regulator integrated circuit inside a rubber protection near the output wires. This device is used to create a minimum load for the +5 V output, allowing the power supply to turn on.
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 OCZ 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.
In the next page we will have a more detailed discussion about the components used in the GameXstream 700 W.
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 OCZ.
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 GBU605 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. This section 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 bridges would allow this unit to deliver up to 1,104 W without burning this component. Of course, we are only talking about these components, and the real limit will depend on all the other components in this 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 took a look, like Antec Neo 550 HE, Cooler Master iGreen Power 430 W, Corsair HX620W and Thermaltake Toughpower 750 W) and this is the first time we see such design. All other high-end 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.
In 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 at 25° C in pulsating mode, which is the mode used, as the PWM circuit feeds these transistors with a square waveform, or 12.1 A at 100° C in continuous mode. Interesting to note that these are the same transistors used by Corsair HX620W power supply.
The two rectifying bridges are installed on the same heatsink used by the switching transistors.
The primary 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 12.
This power supply uses eight Schottky rectifiers on its secondary 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.
Each MBRP3045N rectifier can handle up to 30 A (15 A per internal diode, 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%.
This would give us a maximum theoretical current of 86 A [(15 A x 4)/(1 - 0.30)] or 1,029 W for the +12 V output, 43 A [(15 A x 2)/(1 - 0.30)] or 214 W for the +5 V output and 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.
In Figure 14, you can see the thermal sensor located under the secondary heatsink, which controls the fan speed acording to the power supply internal temperature.
This power supply uses Taiwanese electrolytic capacitors from Teapo, CapXon and OST. The big electrolytic capacitor from the active PFC circuit is rated 85° C while all other smaller capacitors are rated 105° C.
In Figure 15, you can see GameXstream 700 W label stating all its power specs.
This unit has four +12 V virtual rails, distributed like this:
From the previous page we came with some maximum theoretical numbers for the +12V output (1,029 W), +5 V (214 W) and +3.3 V (141 W).
As we mentioned earlier the maximum current/power each line can really deliver will depend on other components, especially the transformer, the coil, the wire gauge and even the width of the printed circuit board traces used.
We found some funny things on this power supply label.
For the +12 V output OCZ stated 18 A for each one of the power supply four virtual rails. This would give a 216 W per rail or 864 W total – OCZ labeled +12 V total power as 680 W. Oh, there is a small phrase there “Maximum combined current for the +12 V outputs shall be 50 A.” Well, if we do the math, the maximum power for the +12 V outputs combined would be 600 W – and not 680 W as printed on the label. Why printing conflicting numbers?
For the + 5 V output OCZ stated a 30 A maximum current, which translates to 150 W, while for the +3.3 V output the manufacturer stated a 36 A maximum current, or 118.80 W. On the label, however, OCZ says that the combined power of +3.3 V and +5 V outputs is of 155 W (since they are connected to the same transformer output). Here it is funny to notice that Corsair HX620W, a 620 W power supply, has a combined power of 170 W, more than this 700 W power supply.
Anyway, all positive outputs are labeled with a current well below the maximum current each rectifier can deliver.
Unfortunately we don’t have the necessary equipment to make a true power supply review; we would need to create a real 700 W load to check if this power supply could deliver its labeled power or not.
Also, as a final note, OCZ doesn’t specify the temperature under which the power supply is rated. Usually when no temperature is stated, the manufacturers assume 25° C, which is a temperature far below the power supply real working temperature. Keep in mind that the maximum power a power supply can deliver drops as its internal temperature increases.
OCZ GameXstream 700 W power supply specs include:
* Researched at Shopping.com on the day we published this First Look article.
This seems to be a good power supply for its price range. If you are looking for a high-end 700 W power supply with active PFC, 80% efficiency and 120 mm low noise fan, consider OCZ GameXstream 700 W. It also carries a three-year warranty, which is great.
Internally we found out that this power supply uses three transistors on its active PFC circuit, which is great – power supplies with active PFC usually have only two transistors. We also liked the idea of using a bigger L-shaped heatsink on the secondary connected to the power supply housing.
However we found out that this power supply doesn’t have a MOV (surge suppressor), which is a sin on a high-end power supply.
This power supply also misses two protections compared to competing products: over power (OPP) and under voltage (UVP). However, it has short-circuit (SCP), over current (OCP) and over voltage (OVP) protections, which is enough for the average user. We should also note that power supplies carrying all these five protections are more expensive than OCZ GameXstream 700 W.
Compared to competing products, GameXstream 700 W also does not provide a modular cabling system. If you are looking for this feature, you should consider other product. However, we must note again that this power supply from OCZ is cheaper than competing products with this feature (just to put things into perspective, HX620W from Corsair is between USD 30 and USD 60 more expensive than this power supply and is a 620 W unit).
As for the temperature, OCZ does not state under which temperature they labeled their power supply. Why this is important? The higher the internal power supply temperature, the lower power it can deliver. Usually when no temperature is mentioned, the manufacturer assumes 25° C. You will never get 25° C inside a power supply; typical real-world values are found between 35° C and 40° C. So a power supply labeled at 25° C may not deliver its labeled power when running in the real world.
Unfortunately we do not have a load tester to pull 700 W from this power supply, so we cannot say if this power supply can really deliver its labeled 700 W or not (an equipment like this costs around USD 10,000 in the US and we hope to buy one someday).
It seems that OCZ also saved some bucks on the electrolytic capacitors: they are all Taiwanese and not Japanese like some competing products.
We are not saying this is a bad product, on the contrary. For its price range it is a really good option if you are looking for a good 700 W power supply and want to save some bucks.