XFX Pro Series 850W Power Supply Review

1. Introduction2. The XFX Pro Series 850W Power Supply (Bundle)3. The XFX Pro Series 850W Power Supply (External)4. The XFX Pro Series 850W Power Supply (Internal)5. Testing Methodology and Results6. Closing Thoughts7. View All Pages

Additional technical assistance: Peter McFarland and Jeremy Price.

Correctly testing power supplies is a complex procedure and KitGuru have configured a test bench which can deliver up to a 2,000 watt DC load. Due to public requests we have changed our temperature settings recently – previously we rated with ambient temperatures at 25C, we have increased ambient temperatures by 10c (to 35c) in our environment to greater reflect warmer internal chassis conditions.

We use combinations of the following hardware:
• SunMoon SM-268
• CSI3710A Programmable DC load (+3.3V and +5V outputs)
• CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• Extech Power Analyzer
• Extech MultiMaster MM570 digital multimeter
• SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa)
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA

DC Output Load Regulation
Combined DC Load	+3.3V		+5V		+12V		+5VSB		-12V
	A	V	A	V	A	V	A	V	A	V
100W	1.58	3.34	1.78	5.03	6.65	12.08	0.50	5.05	0.20	-12.08
225W	3.70	3.34	3.85	5.02	15.54	12.07	1.00	5.03	0.20	-12.07
450W	7.51	3.33	8.40	5.02	30.67	12.06	1.50	5.02	0.30	-12.05
675W	11.32	3.32	12.41	5.01	47.48	12.03	2.00	5.01	0.50	-12.03
850W	1.29	3.30	1.11	5.00	71.00	12.00	0.50	4.99	0.20	-12.01

The Pro 850W delivered excellent load regulation on all output channels across a wide range of loads. These are fantastic results and the +3.3V and 5V rails remained firmly within +/-2% of the nominal voltage instead of the recommended +/-5% and the +12V rail held within +/- 1%, even when it was forced to deliver over 70 Amps.

XFX Pro Series 850W	Maximum Load
	923.8W

We managed to coax 923.8W from the supply before it shut down gracefully. It was able to maintain a 900W output for a long period of time.  The overcircuit protection system is working perfectly. It shut down until we acted more sensibly with our equipment.

Next we want to try Cross Loading. This basically means loads which are not balanced. If a PC for instance needs 500W on the +12V outputs but something like 30W via the combined 3.3V and +5V outputs then the voltage regulation can fluctuate badly.

Cross Load Testing	+3.3V		+5V		+12V		-12V		+5VSB
	A	V	A	V	A	V	A	V	A	V
760W	1.0	3.34	1.0	5.03	65.0	12.07	0.2	-12.08	0.50	5.02
165W	15.0	3.28	18.0	4.98	2.0	12.02	0.2	-12.02	0.50	5.01

The XFX Pro Series 850W handled the cross loading tests very well with only very minor levels of fluctuation under load.

We then used an oscilloscope to measure AC ripple and noise present on the DC outputs. We set the oscilloscope time base to check for AC ripple at both high and low ends of the spectrum.

ATX12V V2.2 specification for DC output ripple and noise is defined in the ATX 12V power supply design guide.

ATX12V Ver 2.2 Noise/Ripple Tolerance
Output	Ripple (mV p-p)
+3.3V	50
+5V	50
+12V1	120
+12V2	120
-12V	120
+5VSB	50

Obviously when measuring AC noise and ripple on the DC outputs the cleaner (less recorded) means we have a better end result. We measured this AC signal amplitude to see how closely the XFX unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load	+3.3V	+5V	+12V	5VSB
100W	5	5	5	5
225W	5	5	10	5
450W	5	5	15	10
675W	10	10	15	15
850W	10	10	20	15

Ripple results are well within the parameters set down in the ATX12V Ver 2.2 standard. +3.3V and +5V are extremely impressive and the +12V rail is also very stable, peaking at 20mv. This is the best result from the three XFX Pro series PSU's we have tested to date.

Efficiency (%)
100W	85.41
225W	86.89
450W	87.84
675W	85.21
850W	83.91

These efficiency results are great for a 80 Plus Bronze certified supply, hitting 87.84% at around 50% load. At full load the efficiency drops to just under 84%, which is very impressive.

We take the issue of noise very seriously at KitGuru and this is why we have built a special home brew system as a reference point when we test noise levels of various components. Why do this? Well this means we can eliminate secondary noise pollution in the test room and concentrate on components we are testing. It also brings us slightly closer to industry standards, such as DIN 45635.

Today to test the Power Supply we have taken it into our acoustics room environment and have set our SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa) one meter away from the unit. We have no other fans running so we can effectively measure just the noise from the unit itself.

As this can be a little confusing for people, here are various dBa ratings in with real world situations to help describe the various levels.

KitGuru noise guide
10dBA – Normal Breathing/Rustling Leaves
20-25dBA – Whisper
30dBA – High Quality Computer fan
40dBA – A Bubbling Brook, or a Refridgerator
50dBA – Normal Conversation
60dBA – Laughter
70dBA – Vacuum Cleaner or Hairdryer
80dBA – City Traffic or a Garbage Disposal
90dBA – Motorcycle or Lawnmower
100dBA – MP3 Player at maximum output
110dBA – Orchestra
120dBA – Front row rock concert/Jet Engine
130dBA – Threshold of Pain
140dBA – Military Jet takeoff/Gunshot (close range)
160dBA – Instant Perforation of eardrum

Noise (dBA)
100W	27.1
225W	29.1
450W	29.9
675W	32.8
850W	34.8

Our noise results are (not surprisingly) very close to the XFX Pro Series 750W PSU we reviewed last week. At around 70% load, the PSU become audible, rising to a maximum of 34.8 dBa at 100% load. It isn’t the world’s quietest PSU by a long shot, but at realistic load levels it should not annoy the user base.

Temperature (c)
	Intake	Exhaust
100W	35	37
225W	35	38
450W	38	42
675W	42	52
850W	45	54

The large fan pushes a lot of airflow under load which helps to keep the components in check. At around 70-80% load, the fan speeds start increasing considerably. At full load we reach a 9c above ambient intake threshold.

Maximum load	Efficiency
923.8W	81.2

Pushing the PSU above its rated limits generates an efficiency level of around 81.2%. This is not a viable ‘real world’ situation, but its interesting nonetheless.

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