Nexus RX-8500 850 W and RX-1k 1000 W power supplies

Posted by: Suvirintojas Date: 2010-02-05 22:01:41
Category: Cases/PSUs

We know that a decent 500 W power supply will be more than enough for a home computer, even a reasonably powerful machine with a single graphics card will cause no problems to a decent power supply of this power. But there are enthusiasts out there, who might want to build a SLI or Crossfire setup with up to 4 GPUs. And they need power.

Today we will be looking at two power supplies from Nexus, the RX-8500 (850 W) and the RX-1k (1000 W), both of which should provide enough power for a high end PC with multiple graphics cards.

Contents

About the manufacturer
Packaging and contents
Specifications
Power supplies
Testing
Conclusions


About the manufacturer

Nexus Technology was established in 2000 in the Netherlands and have since then concentrated on computer hardware products that help to reduce the noise of your computer and improve heat conductivity as well as airlflow. Nexus' goal is building a strong and reliable trademark for silent computing.

Nexus has a wide range of products. It specializes mostly in coolers (heatsinks and fans), computer cases and various accessories. Although the company does not make them in house, Nexus has also a range of computer power supplies of various power.

Packaging and contents

Both power supplies come in identical black boxes with orange sides (these are the traditional Nexus colours) with not too many text on it. The logo of Nexus, the model number and a picture of the PSU is on the front side. On the back side we see some basic information about power supply efficiency, noise level measurements and other features. The most useful information here is the the data about the connectors of the power supply and the power distribution along the rails. On the side Nexus includes graphs with noise levels and efficiency numbers at different loads. And that is pretty much all the information you would like to find on a package of a power supply.

Inside the boxes we again see the same view: the PSU is sitting between two pieces of foam and all the cables are packed in a separate box. Everything is very tidy, but Nexus does not include an AC power cable with its RX-8500 and RX-1k power supplies, so you will have to get one yourself. Everything the company includes is the PSU and the modular cables.

Specifications

Both of the power supplies are full range (110-250 V) and compatible with the ATX 2.2 standard have active power factor correction circuits and efficiencies over 80%, though we cannot see the 80 Plus logo anywhere. This is because Nexus didn't send their power supplies to get tested to save cost, but it guarantees, that these power supplies are 80Plus compliant.




Efficiency of RX-8500 and RX-1k

While I like the idea of noise level and efficiency level diagrams on the product web page and on the box, I would like to see the information about what distance from the PSU are Nexus testing the supplies, the ambient temperature and what AC voltage is being supplied to the PSU during efficiency measurements.





The power distribution is somewhat different on the 850 and 1000 W models. While both supplies have the same output capabilities for the +3.3 and +5 volt lines, which is 24 and 30 amps respectively with the maximum combined power of 170 W, the +12 V rails are not similar at all. The RX-8500 has its +12V rails split into four virtual rails with the theoretical maximum current of 20 A on each of them. The combined +12V power of 760 W is very decent for a PSU rated at 850 W. Though we will see later what the real maximum currents for the +12V rails are.

The RX-1k has a more favourable approach to the +12V delivery with a single rail, rated at 75 amps. A single rail is more convenient as you don't have to worry if you are pulling too much amps from a one rail. This lets you connect everything basically however you like. This supply, according to its specifications, can deliver up to 900 W using only the 12 V rail, which is also good.

The main cables in both PSUs have wire gauges of 16 AWG. All their cables are sleeved and most of them are modular. The hardwired cables for both supplies are the 24 pin ATX motherboard cable (45 cm), 8 pin EPS +12V cable (45 cm), a 4 pin P4 +12V cable of the same length (which really is not a necessity) and two 45 cm PCI-E 8 pin power plugs.

Now for the modular cables. The RX-8500 has two additional PCI-E 6 pin cables (50 cm each), two cables with three SATA connectors (50 + 20 + 20 cm) and two cables with three molex and one floppy connector (50 + 15 + 15 + 15 cm). The RX-1k has one additional SATA and one additional molex cables. To better illustrate the quantity of the cables, here are the diagrams from Nexus' website.




Nexus RX-8500 cables



Nexus RX-1k cables

What I miss here are a couple more PCI-E power cables, especially for the 1000 W model. A triple SLI or Crossfire setup would run just fine on these PSUs, but for that you might need two additional PCI-E power cable adapters. The less powerful RX-8500 at least has two connectors for modular PCI-E power cables, while the RX-1k, which actually needs them more, doesn't.

With the RX-1k the power distribution is very simple. It has a single +12 V rail, so every cord connects to it. The RX-8500, however, has four +12 V rails, which are limited by the implemented OCP. One rail is dedicated for all the molex and SATA power cables, as well as the motherboard power delivery. A separate rail is dedicated to the CPU. Both the 4 and 8 pin processor power cables connect to this rail. The other two rails are dedicated to the graphic cards. One hardwired cable to one rail's output, ant the second one - to another. Up to two more cables can be connected to each rail (two are included with the supply).


Power supplies

Both supplies are almost identical from the outside and share the same dark glossy paint job. The RX-8500 and RX-1k have identical dimensions of 150x86x165 mm which are bigger than a standard ATX supply, but quite small for high power supplies.

On one side of the PSUs there are the stickers with the specifications and on the other - a serial number. The PSUs have a traditional design with the fan on the bottom (or the top, depending on the orientation). The fan intakes air and, after it goes through all the components, pushes it through the honeycomb grill at the back.

At the opposite site we find the hardwired cables and modular plugs. It is nice to see, that Nexus has marked, which connector belongs to which rail on the 850 W model. As I mentioned before, the RX-1k has two connectors for PCI-E power cables less, that the RX-8500.

I couldn't take a look at the RX-1k insides, as I had to give it away, but judging from the single +12V rail, it might use a different design than its less powerful brother.

Opening the RX-8500 reveals very tightly packed components. Two decently sized aluminum heatsinks are cooling the transistors and rectifiers with a temperature sensor (the fan speed changes according to its data) connected to the second heatsink. The PSU has not one, but two main transformers sharing the load. There also two rectifying diode bridges cooled by the same heatsink in the corner, near the second half of the transient filtering (additional components are installed near the AC power plug). On the opposite side we see switches for manually adjusting the output voltages of the rails. Most of the capacitors in this PSU is made by TEAPO and rated at 105 degrees Celsius with the huge main capacitor (450V, 560uF) rated at 85 degrees. The 13.5 cm 11 blade fan, used in this supply is made by Muhua Industrial Co., and is rated at 0.25 A at 12 V. We didn't find no further details on this fan on the web.


Testing

The testing of power supplies requires some additional devices. First of all, a computer is not a very good load, as you can't control its power draw very precisely and you will not be able to push the power supplies to their maximum rated power. That's why we use a simple hand made device which we called Anatolijus. It is a device with bunch of resistors put together in an old PC case. It allows us to fully load power supplies of up to ~1500 W. As it is an analog device, it allows us to control the currents drawn from the PSU only roughly (for the +3.3 and +5 V rails a minimum step is ~4 A and for the +12 V - ~2 A). That's why we measure the currents during every test.

We perform 4 tests for every PSU: with 20, 50, 75 and 100% (or at least, the closest we can get to these values) of its rated maximum power. Each time we measure the voltages of the rails with a digital multimeter to determine, if they are within the allowed range of 5%, defined by the ATX standard. We also measure the temperature (with an IR thermometer) and acoustics (5 cm from the PSU). Such small distance is chosen because of the noise of Anatolijus and a simple domestic heater we use to keep the ambient temperature for the PSU as close to 40 degrees Celsius as possible, imitating the working conditions in a hot computer case with additional components, that tend to generate heat.

We also calculate the power supplies efficiency using a simple power meter (PM-300), which measures the power draw from the socket. All tests are performed with the supply connected to a 230 V, 50 Hz socket. Efficiency with 115 V, 60 Hz sockets at all loads would typically be a couple percent lower.

The RX-8500 alone draws 20 W from the socket with the power switch on and 6 W with the power switch off. The RX-1k has even higher numbers of 37 and 22 W which could have a small impact on your electricity bills. Protection from shorts worked on both PSUs. I didn't push the 1000 W PSU's 12V rail to the limit as I felt quite sorry for Anatolijus, which in future might get a cooling upgrade. Either way, a single rail will not cause problems with even the most powerful hardware. When I tried to pull more current from a single rail, even ~40 amps would not trigger the OCP protection. That means that you are not likely to encounter problems because of limits the PSU might have for a single +12 V rail.

Loading tests

Results for the Nexus RX-8500:





Results for the Nexus RX-1k:





Both power supplies performed fairly well in our tests, although there are some points that need mentioning. The efficiency levels of both PSUs were not great, but stayed over the 80% mark, though at low load the RX-1k's efficiency dropped bellow 80%. Overall the efficiency of the 850 W unit is better.

Both supplies showed similar noise level results with the RX-8500 being a little louder in some cases, though running a bit hotter. This might be because of not ideally equal ambient temperatrure. Because of the additional noise sources the readings of our dBA meter seem very high, but at loads of 20 or 50% the supplies are barely audible even from a close distance. Bare in mind, that the ambient temperature during our tests are higher than typical temperatures in a computer case. The temperatures of either supply are not dangerous.

Overall the RX-1k provided very stable voltages on all rails, especially on the +12V. The RX-8500's voltages also stayed within the 5% deviation for every measurement, except for one. At the last load test the +3.3V voltage went out of the ATX spec. I must admit, that the load on the +3.3V line was very high looking at today's standards, but the +3.3/5 V combined power was lower than the maximum allowed.


Conclusions

Both PSUs from Nexus proves to be solid performers. They don't have the highest efficiency numbers, but they are at 80% or higher. Even at high loads they provide stable voltages, with the exception of the 3.3 V rail at high loads on the RX-8500 model. The +12 V voltage deviation stayed well within 5%, required by the ATX standard. At medium loads these supplies perform very quiet.

The biggest problem that I see with these PSUs are the number of connectors for the graphics cards. Unless you have (triple) SLI/ Crossfire, you simply don't need so much power and pay more for a power supply. But with more than two video cards you might become short of PCI-E power cables, which Nexus could have included with the supply (at least for the 1000 W model).

I can say, that it is "safe" to buy any of these PSUs. They might not be great, but they are fairly good. Their current price is quite competitive. The Nexus RX-8500 can be bought for about 150 USD, and the RX-1k - for 200, so they are decently priced power supplies for your overclocked multiGPU rig.