XFX is releasing their PRO series of power supplies, with single +12 V rail, DC-DC secondary design, and 80 Plus Bronze certification. So far three models were released: 650 W, 750 W, and 850 W. We have already tested the 650 W and the 750 W models, and both proved to have terrific cost/benefit ratios. Let’s see if the 850 W model follows the same path.
Like other power supplies from XFX, members of the PRO series are manufactured by Seasonic.
Figure 1: XFX PRO 850 W power supply
Figure 2: XFX PRO 850 W power supply
The PRO 850 W is 7.1” (180 mm) deep, with a 135 mm dual ball bearing fan (ADDA ADN512UB-A90) on its bottom part.
The new XFX PRO 850 W doesn’t have a modular cabling system. All cables are protected with nylon sleeves. The power supply comes with the following cables:
- Main motherboard cable with a 20/24-pin connector, 22.8” (58 cm) long
- One cable with two ATX12V connectors that together form an EPS12V connector, 23.6” (60 cm) long
- Two cables with one six-pin connector for video cards each, 22.8” (58 cm) long
- Two cables with one six/eight-pin connector for video cards each, 22.8” (58 cm) long
- Two cables with four SATA power connectors each, 15” (38 cm) to the first connector, 5.9” (15 cm) between connectors
- One cable with three SATA power connectors, 15” (38 cm) to the first connector, 5.9” (15 cm) between connectors
- One cable with four standard peripheral power connectors, 15” (38 cm) to the first connector, 5.9” (15 cm) between connectors
- One cable with three standard peripheral power connectors and one floppy disk drive power connector, 15” (38 cm) to the first connector, 5.9” (15 cm) between connectors
All wires are 18 AWG, which is the minimum recommended gauge.
The only difference in cable configuration compared to the configuration used on the 650 W and 750 W models was the addition on one cable with three SATA connectors, making this unit to have a total of 11 SATA power connectors, which is great. We think the manufacturer could have added two more video card power connectors in order to allow the installation of three high-end video cards without the need for adapters.
Let’s now take an in-depth look inside this power supply.
[nextpage title=”A Look InsideThe XFX PRO 850 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.
On this page we will have an overall look, and then in the following pages we will discuss in detail the quality and ratings of the components used. The printed circuit board used by the PRO 850 W is identical to the one used by the PRO 650 W and PRO 750 W.
Figure 7: Printed circuit board
[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.
The transient filtering stage of the XFX PRO 850 W is impeccable, coming with all required components plus one extra X capacitor and four extra Y capacitors.
Figure 8: Transient filtering stage (part 1)
Figure 9: Transient filtering stage (part 2)
In the next page we will have a more detailed discussion about the components used in the XFX PRO 850 W.
[nextpage title=”Primary Analysis”]
On this page we will take an in-depth look at the primary stage of the XFX PRO 850 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses two GBU806 rectifying bridges connected in parallel, attached to an individual heatsink. Each bridge supports up to 8 A at 100° C so, in theory, you would be able to pull up to 1,840 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,472 W without burning themselves out. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply. These are the same bridges used by the 750 W model. The 650 W model uses two 6 A bridges here.
The active PFC circuit uses two SPP24N60C3 MOSFETs, which are capable of delivering up to 24.3 A at 25° C or up to 15.4 A at 100° C (note the difference temperature makes) in continuous mode, or up to 72.9 A in pulse mode at 25° C, each. These transistors present a 160 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will achieve a higher efficiency. It is interesting to note how, in order to improve thermal dissipation, the manufacturer added a metallic plate between these transistors and the aluminum heatsink (see Figure 11). These transistors are identical to the ones used in the 750 W model, and more powerful than the ones used in the 650 W model.
Figure 11: Active PFC diode and transistors
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. The XFX PRO 850 W uses two 330 µF x 400 V capacitors connected in parallel; this is the equivalent of one 660 µF x 400 V capacitor. These capacitors are Japanese, from Rubycon, and labeled at 105° C. The 750 W model uses one 330 µF x 400 V and one 220 µF x 400 V capacitor, and the 650 W model uses two 220 µF x 400 V capacitors in this stage.
In the switching section, another two SPP24N60C3 transistors are used, installed in the now traditional two-transistor forward configuration. The 750 W and 650 W models use SPP20N60C3 transistors, which have a lower current limit.
Figure 12: One of the switching transistors
The primary is controlled by a CM6802 active PFC/PWM combo controller.
Figure 13: Active PFC/PWM combo controller
Now let’s take a look at the secondary of this power supply.
[nextpage title=”Secondary Analysis”]
This power supply uses a DC-DC project in its secondary, meaning that this unit is basically a +12 V power supply. The +5 V and +3.3 V outputs are produced by two smaller switching power supplies connected to the +12 V rail. This design is used to increase efficiency.
The +12 V output makes use of six SBR30A50CT Schottky rectifiers, each one capable of handling up to 30 A (15 A per internal diode at 110° C, 0.55 V maximum voltage drop). The 750 W model has five of these rectifiers, while the 650 W model has four of them. This gives us a maximum theoretical current of 129 A or 1,543 W for the +12 V rail.
As explained, the +5 V and +3.3 V outputs are generated using two DC-DC converters (i.e., two switching power supplies). Usually power supplies using this design have these two converters installed on separate daughterboards, but in the XFX PRO 850 W they are available on the same board, shown in Figures 15 and 16. The two converters are managed by the same PWM chip (APW7159), and use seven APM2556N MOSFET transistors, each one being able to handle up to 160 A at 25° C or 90 A at 100° C with an RDS(on) of only 4.5 mΩ. The DC-DC converter board is identical to the one used in the PRO 750 W and in the PRO 650 W.
Figure 15: The +5 V and +3.3 V DC-DC converter
Figure 16: The +5 V and +3.3 V DC-DC converter
The secondary is monitored by a PS223 integrated circuit, which supports over voltage protection (OVP), under voltage protection (UVP), over current protection (OCP), and over temperature protection (OTP). This integrated circuit has four OCP channels (+3.3 V, +5V and two +12 V), but the manufacturer decided to use only one of the +12 V channels, making this a single-rail power supply.
All electrolytic capacitors used in the secondary are also Japanese, from Chemi-Con, and labeled at 105° C.
[nextpage title=”Power Distribution”]
In Figure 18, you can see the power supply label containing all the power specs.
Since this unit has a single +12 V rail, there is not much to talk about here.
Let’s now see if this power supply can really deliver 850 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 the behavior of the reviewed unit 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 powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (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. In 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 our tests, the +12VA and +12VB input were connected to the power supply single +12 V rail (the EPS12V connector was installed on the +12VB input of our load tester).
|Input||Test 1||Test 2||Test 3||Test 4||Test 5|
|+12VA||6 A (72 W)||13 A (156 W)||18.5 A (222 W)||25 A (300 W)||31 A (372 W)|
|+12VB||6 A (72 W)||12 A (144 W)||18.5 A (222 W)||25 A (300 W)||31 A (372 W)|
|+5V||2 A (10 W)||4 A (20 W)||6 A (30 W)||8 A (40 W)||10 A (50 W)|
|+3.3 V||2 A (6.6 W)||4 A (13.2 W)||6 A (19.8 W)||8 A (26.4 W)||10 A (33 W)|
|+5VSB||1 A (5 W)||1.5 A (7.5 W)||2 A (10 W)||2.5 A (12.5 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||173.1 W||349.1 W||511.8 W||686.4 W||847.1 W|
|% Max Load||20.4%||41.1%||60.2%||80.8%||99.7%|
|Room Temp.||46.4° C||46.8° C||47.6° C||47.4° C||49.4° C|
|PSU Temp.||40.5° C||44.2° C||49.8° C||49.5° C||50.2° C|
|Ripple and Noise||Pass||Pass||Pass||Pass||Pass|
|AC Power||203.5 W||404.4 W||598.2 W||819.0 W||1037.0 W|
|AC Voltage||118.7 V||116.8 V||115.8 V||112.4 V||110.0 V|
The XFX PRO 850 W can really to deliver its labeled wattage at high temperatures.
Efficiency was very good, between 81.7% and 86.3%. The 80 Plus Bronze certification requires a minimum 82% efficiency at light (20%) and full loads, and this unit presented 81.7% efficiency at full load. This happens because the 80 Plus tests are conducted at 23° C, while ours were done between 46° C and 49° C, and efficiency drops with temperature. But this value was close enough of the advertised efficiency. Also, the efficiency at light load (20% load, 170 W) was very high at 85%.
Voltage regulation was superb, with all voltages within 3% of their nominal values, including the -12 V output. The ATX12V specification allows voltages to be up to 5% from their nominal values (10% for the -12 V output). Therefore this power supply presents voltages closer to their nominal values than necessary all the time.
Noise and ripple levels were always extremely low. Below you can see the results for the power supply outputs during test number five. The maximum allowed is 120 mV for the +12 V and -12 V outputs, and 50 mV for the +5 V, +3.3 V, and +5VSB outputs. All values are peak-to-peak figures.
Figure 19: +12VA input from load tester during test five at 847.1 W (17.8 mV)
Figure 20: +12VB input from load tester during test five at 847.1 W (29 mV)
Figure 21: +5V rail during test five at 847.1 W (8.6 mV)
Figure 22: +3.3 V rail during test five at 847.1 W (11.4 mV)
Let’s see if we can pull even more from the XFX PRO 850 W.
[nextpage title=”Overload Tests”]
Below you can see the maximum we could pull from this power supply. We couldn’t pull more than that because the power supply shut down, showing that its protections are working just fine.
|+12VA||33 A (396 W)|
|+12VB||33 A (396 W)|
|+5V||22 A (110 W)|
|+3.3 V||22 A (72.6 W)|
|+5VSB||3 A (15 W)|
|-12 V||0.5 A (6 W)|
|% Max Load||116.2%|
|Room Temp.||49.1° C|
|PSU Temp.||51.1° C|
|AC Power||1,274 W|
|AC Voltage||107.1 V|
[nextpage title=”Main Specifications”]
The specs of the XFX PRO 850 W include:
- Standards: ATX12V and EPS12V (exact versions not informed)
- Nominal labeled power: 850 W
- Measured maximum power: 987.8 W at 49.1° C ambient
- Labeled efficiency: Up to 85%, 80 Plus Bronze certification
- Measured efficiency: Between 81.7% and 86.3% at 115 V (nominal, see complete results for actual voltage)
- Active PFC: Yes
- Modular Cabling System: No
- Motherboard Power Connectors: One 20/24-pin connector and two ATX12V connectors that together form an EPS12V connector
- Video Card Power Connectors: Two six-pin connectors and two six/eight-pint connectors on separate cables
- SATA Power Connectors: 11 on three cables
- Peripheral Power Connectors: Seven on two cables
- Floppy Disk Drive Power Connectors: One
- Protections (as listed by the manufacturer): Over power (OPP), over voltage (OVP), over current (OCP), over temperature (OTP), and short-circuit (SCP)
- Are the above protections really available? Yes, under voltage protection (UVP) pres
ent but not listed by the manufacturer
- Warranty: Five years
- Real Manufacturer: Seasonic
- More Information: https://xfxforce.com
- Average Price in the US*: USD 130.00
* Researched at Newegg.com on the day we published this review.
The XFX PRO 850 W provides a terrific value for users looking for a good and affordable 850 W unit. It passed our tests with flying colors, with good efficiency, outstanding voltage regulation, ultra-low noise and ripple levels, and good cable configuration (even though we prefer to see six cables for video cards instead of “only” four on 850 W units).
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