OCZ ModXstream Pro 500w Page: 1

PSU's are a real case of you get what you pay for. The cheaper, non branded PSU's are often incredibly unstable, in-efficient and can fail within a few months of purchase. Installing such PSU's in a high-end PC is akin to having a death wish, but only for your hardware. Not only can  low or poorly filtered voltages cause damage to devices that don't employ their own filtering circuits, but surges that often occur when a PSU fails have the ability to decimate every single component inside your precious PC system.

A few months ago we reviewed OCZ's 780w ModXstream model, whilst it certainly scored well in our testing and managed to bag our Recommended award, there was still room for improvement. This undoubtedly spurred the release of the ModXstream Pro series announced back in August. Equipped with a larger fan, new internals and a refreshing new look,  the 'Pro' is aimed at bringing down noise and improving on the performance of it's predecessor. It should certainly come as no surprise then, that when OCZ asked us if we would like to take a look, we couldn't resist.

Here are the full specifications:

150 x 160 x 86mm (W x L x H)
ATX12V v2.2 and EPS12V
Typical load 86% Efficiency
80+ Certified
Overvoltage/OverPower/Short-Circuit protection
(.99)Active PFC
MTBF: 100,000 hours @ 25C

1 x 20/24-pin ATX
1 x 8-pin CPU
1 x 4-pin CPU

Modular Connectors:
1 x 6-pin PCI-E
1 x 6+2-pin PCI-E
4 x Peripheral
2 x Floppy
6 x SATA

As we can see, the ModXstream has a fairly average spec for a modern PSU, with 86% efficiency and 100,000hr MTBF at 25c.  The PCI-e connectors are also noteworthy, with OCZ opting for 1x 6-pin and 1x 8-pin plugs allowing for the unit to be used with a wide range of modern graphics cards such as the GTX280, 4870x2 and GTX295. Of course, whether the 500w unit has enough gusto to power such cards in addition to a full PC system is yet to be determined.

Unlike the OCZ EliteXstream we reviewed a while back the ModXStream Pro features two +12v rails rated limited to 18A each. Interestingly OCZ rate the maximum output of both rails as 423w which when converted into amps produces a result of 36A (or 18A x2). This in essence indicates that providing the draw on the +5v and +3.3v rails comes to less than 68w, the +12v1 and +12v2 rails can deliver their full 18A ratings.

OCZ ModXstream Pro 500w Page: 2
Packaging and First Impressions

Some PSU's come in incredibly elaborate packaging, such as the Tagan Turbojet 1100w, which came in a suitcase. OCZ however, have chosen to keep things simple and go with an ordinary box. This not only keeps manufacturing costs down, but shipping as well.

OCZ ModXStream 500w Packaging OCZ ModXstream 500w

As you can see the packaging uses a uniform layout front and back; a swooping black area around the edges with the headline features, whilst a red section has all the smaller details. There is a picture of the front and back of the PSU on either side, and a small carry handle on the top of the box.

OCZ ModXstream 500w

Inside the box we have: the PSU, bag of modular cables and the user manual. In with the modular cables is a set of screws for installation and a UK mains power lead. The PSU is close to gun metal grey in colour, and the paint looks nicely done. The big fan grill dominates the top of the PSU, and big fans mean less noise in most cases. So far so good..
OCZ ModXstream 500w Fan OCZ ModXstream Side

The fan grill features the OCZ logo at its centre, and looks fairly unrestrictive airflow-wise, whilst also stopping fingers and other objects from entering the insides of the PSU. The side of the PSU has the ModXstream label, along with various other labels for certifications.
OCZ ModXstream Modular ports OCZ ModXstream Modular Ports

Round the back we have the modular connectors. These are similar to those used on other products and use the tried and tested PCI-e style layout. The modular leads clip in, with a little latch on top securing them in place. Modular leads not only reduce cable clutter making your case look nicer, but can also improve airflow, lowering overall system temperatures.

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Up Close

As with a lot of things, it's what's inside that counts. This is where the PSU performs its magic, transforming the unfriendly AC into computer friendly DC current: breaking down the 240VAC into the various low voltage rails. After removing four screws from the top of our unit, we were in...

OCZ ModXstream Fan

The fan is manufactured by Globe Fan, and is rated at 0.33A @ 12v. Unfortunately we couldn't find any specs for the fan on Globe Fans website at the time of writing. Interestingly, OCZ have covered off part of the fan with a bit of perspex. This may have been done so that air can escape at the back of the unit, rather than constantly being pushed down.

OCZ ModXstream Inside OCZ ModXstream Transformers

The internals of the ModXstream Pro are split into three sections, with MOSFET heatsinks dividing each section up. In the top section, we have a single large capacitor. It is preferred to have multiple smaller capacitors as this reduces power ripple, but it shouldn't be too big a problem. The capacitor appears to be made by EPCOS, a German manufacturer and features the following markings: 330uF / 400v / 85c. In the middle section we have two transformers, one for the 12v and the other most likely for 3.3v/5v.


Being a modular cables not all the cables are attached to the PSU. Instead only a few of them are left attached to the PSU and the rest are detachable. This way only the cables you need are attached, minimising excess cable mess within your case.

OCZ ModXstream Cabling

The cables already attached to the PSU are as follows: 4-Pin P4 Connector, 8-Pin EPS connector, 20+4-Pin ATX power cable. These are pretty much the bare minimum for any PC. It would have been nice to have the 4-Pin and 8-Pin connectors being modular, as one of these is guaranteed not to be in use.
OCZ ModXstream Cables

There is a nice selection of cables included in the box. In the top left we have the PCI-e 6-pin and 8-pin leads. In the middle we have the UK mains power lead. Then, around the edges we have the molex and SATA power leads. In total you can connect 6 SATA devices, 4 Molex devices and 2 Floppy devices. The SATA's come in a group of three, which is handy as most case caddies take 3 drives - Well thought out OCZ.
OCZ ModXstream PCI-E OCZ ModXstream Molex Cabling

Here we have the dual PCI-e Connectors and molex leads. The 8-pin PCI-e can be converted to a 6-pin lead by removing the two extra pins. The Molex connectors have two standard molex connectors, then a floppy connector on the end. It would have been far more useful to have three molex connectors, with a floppy adaptor in the box for those that still need them.

OCZ ModXstream Pro 500w Page: 4
Load Configuration

To provide our readers with the most accurate results, Overclock3D uses a professional grade SunMoon SM-268+ ATE load tester capable of placing a sustained load of 1690w across a total of six rails (including +5vsb and -12v) on the PSU. Unlike our previous resistor based load tester the SM-268+ gives us the ability to adjust amperage loads in increments as small as 0.01A while also measuring voltages and wattage readings on-screen.

During todays tests we will be placing the ModXstream under 25%, 50%, 75% and 100% load levels and taking voltage readings at every stage. The chart below details the exact amperage load placed on each rail of the PSU at the aforementioned load levels:

Input Load
  25% 50% 75% 100%
 +3.3v 3.75A 7.5A 11.25A 15.00A
 +5.0v 3.75A 7.5A 11.25A 15.00A
 +12v1  3.75A 7.5A 11.25A 15.00A
 +12v23.75A 7.5A 11.25A 15.00A
 +5vsb 0.625A 1.2A 1.875A 2.50A
 -12v 0.075A 0.150A 0.225A 0.300A
 Total *
 126W 252W 376W 498W

**Total wattage is taken directly from the SM-268+ readout rather than a calculation of the amperage loads.


With testing done at the above settings, we were able to achieve the following results from the ModXstream 500w.

Output Voltages
  25% 50% 75% 100%
 +3.3v 3.37v 3.34v 3.30v 3.26v
 +5.0v 5.01v 4.95v 4.89v 4.83v
 +12v1 / +12v2 * 12.14v 12.05v 11.95v 11.85v
 +5vsb 5.11v 5.04v 4.99v 4.93v
 -12v -12.02v -12.11v -12.21v -12.31v

As you can see, the ModXstream 500w has fairly good voltage regulation, with all the voltages well within the ATX specification. The voltages did shift quite a lot as we applied more and more load, with most of them going from small overvolts to a slight undervolt. However, since this is well within the 5% ATX tollerance level, it's nothing to worry about.


Efficiency tests are performed by measuring the wattage consumed by the power supply at the mains (Mains Draw) against the wattage readout displayed on the SM-268+ load tester (PSU Load). These results should offer around 99% accuracy placing them extremely close to results obtained from professional equipment.

  25% 50% 75% 100%
 Mains Draw 150w 296w 444w 602w
 PSU Load
 126w 252w 376w 498w
 Efficiency  84% 85.1% 84.6% 82.7%

Efficiency on the whole was rather good. The 85% achieved between 50-75% is good, but other PSU manufacturers have released models with up to 90% efficiency, so it's nothing ground-breaking. The only minor niggle is the efficiency at 100% load, where it drops to below 83%. However, it is highly unlikely that you will run a PSU that close to its limits, so it shouldn't be a concern the average user.


As with all components in the modern computer system, the performance of a PSU can be directly affected by heat. Excess levels of heat recorded at the PSU's exhaust can indicate that the cooling system is inadequate in keeping the PSU's internal temperature under control which can subsequently lead to a reduction in the maximum power output of the unit. For this reason Overclock3D takes temperature readings from the PSU's intake and exhaust areas after 10 minutes of running at each specified load level. These results can be seen below.

  25% 50% 75% 100%
Intake 22.6°C 23.3°C 23.6°C 23.1°C
Exhaust 31.45°C 34.5°C 36.4°C 37.8°C
 8.85°C 11.2°C 12.8°C 14.7°C

The temperature tests didn't give us any readings to be conerned about, with the PSU staying well within comfortable operating temperatures. The 14cm fan obviously does a great job of cooling, and the cool temperature at which the components operate should ensure a long life span.

OCZ ModXstream Pro 500w Page: 5

The results speak for themselves really, whilst not outstanding, they are very solid indeed. This PSU feels like one of those quiet children at school, that does the work, but doesn't really get noticed. It easily completed all the tests, and passed with flying colours right up to its 500w limit. The modular cables and large fan mean that not only the PSU runs cool, but it also improves airflow within the case. The design of the unit is also worthy of note, with its nice paint job and electroplated grill featuring the OCZ logo.

The only worry we had about the ModXstream 500w was the use of a fairly low spec capacitor. However, having thoroughly tested the unit,  we can safely say it doesn't seem to affect the units performance in any way.

Availability isn't great at the moment, with Specialtech being the cheapest UK supplier. Priced at £49.42, the PSU suddenly stands out from the crowd. It fits into the cheaper end of the 500w scale, yet is extremely quiet, modular and stable. Therefore, we can whole heartedly recommend this PSU, which is simply perfect for all but the most advanced gaming rigs.

+ Modular
+ Quiet
+ Fully sleeved cables
+ Looks nice

The Mediocre
* Single large capacitor rather than many small capacitors
* Efficiency is mediocre at 100% load.

The Bad
- Nothing to report.

Overclock3D would like to thank OCZ for supplying todays review sample. Discuss this review in our forums.