Having recently explored the much more expensive OCZ ZX series, which starts at $170 for the 850w model, we felt it made sense to check out the more mainstream ZT series. Shortly after launching their flagship ZX series OCZ announced the ZT series which would be made up of three unique models.

The base unit, being the 550w model, was pegged at just $100 while the larger 650w and 750w models were given an MSRP of $110 and $120 respectively. However today’s pricing sees the ZT series selling for even less, as the 550w model can be had for just $90 while the 650w version is at $100 and the 750w model just $110.

This means that the OCZ ZT 750w is 35% cheaper than the ZX 850w and just 20% more than the ZT 550w model. Despite being a cut down version of the ZX series, the ZT power supplies still keep many of the features that users find highly desirable, such as the 100% modular system, single +12v rail design, quiet 140mm fan, 5-year warranty and the 80-Plus Certification (though it has been downgraded).

As a side note for those not fussed about the modular design and extensive warranty, there is the even more affordable OCZ ZS series, featuring 750w, 650w and 550w units which are priced at just $100, $80 and $70 in that order.

Getting back to the OCZ ZT series, how does the 750w model at $110 compare to the competition? From Thermaltake we have the Toughpower XT TPX-775M which costs more at $120 and features fewer connectors, the design is also not 100% modular. Representing Corsair is the Enthusiast Series TX750M which costs more again at $130 and again it features fewer connectors while the design is not 100% modular.

Meanwhile it’s a similar case when comparing the OCZ ZT series to power supplies from Seasonic, Silverstone, Cooler Master, Enermax and so on. Therefore in terms of value it appears the ZT series is hard to beat, and with that in mind let’s move on to check out the features in more detail...

The OCZ ZT series utilizes a single +12VDC rail which we much prefer to power supplies that use quad rail designs for example. The 650w model for example has a 62A 12v rail but if it featured a quad design that would mean four 15.5A rails. This becomes a problem when you have a graphics card that is capable of sucking down more than 15.5A as it will cause the system to crash (BSOD) or something to that effect.

The 45A (550w), 54A (650w) and 62A (750w) single rail designs of the OCZ ZT series makes them much harder for SLI/Crossfire graphics cards to max out, and with this arrangement it cannot be done without significantly more hardware added to the system. This kind of arrangement could also produce more stable and better overclocking results.

The OCZ ZT power supplies all utilize a 14cm dual-ball bearing fan made by Yate Loon. The seven blade fan operates at 2800 RPM and is said to move 140 CFM of air while making 48.5dBA of noise. This is a DC fan with a 12v/0.70A rating with the model name D14BH-12.

Finally, the last key feature is the 80-Plus Bronze certification, which means under 20% load the power supply will have an efficiency level of 82%, while this will increase to 85% under 50% load, and finally 82% at 100% load. This means that the ZT power supplies waste 18% or less electricity due to heat when operating at room temperature.

However OCZ also claims that the ZT series will deliver full power continuously 24 hours a day, 7 days a week when operating at temperatures as high as 45 degrees Celsius. Of course we are not sure what this temperature, which is just over two times greater than room temperature, does to the unit’s operating efficiency.

The efficiency of a computer power supply is the amount of energy it supplies, divided by how much energy is input. The remaining energy is converted into heat. For example if a 750w power supply only had an efficiency rating of 60% under full load, it would draw 1250w from the wall, 500w of which would be lost as heat.

However, if we had a 750w unit with an 80% rating, 930w would be drawn from the wall and just 180w would be lost as heat. Finally, the 80-Plus Bronze certification, which calls for a maximum load efficiency of 85%, means that a 750w unit will draw roughly 860w from the wall, which means it will lose just 110w as heat. So the greater the efficiency the more you save on your power bill and the “greener” you will become.

At the business end of the OCZ ZT 550w and 650w power supplies there are nine connectors in total, while the 750w version has twelve due to its additional PCIe support and extra 8-pin CPU connector. In the image below you can see five peripheral/SATA ports and two 8-pin PCIe power connectors (four for the 750w model), along with an 8-pin CPU connector (two for the 750w model) and the 24-pin ATX connector. The PCIe ports are color coded to avoid confusion, though that said, it is not possible to plug a cable in the wrong port anyway.

Each unit features a 24-pin ATX power connector, two EPS/ATX 12V 4+4-pin connectors, nine SATA 5-pin connectors, six 4-pin peripheral connectors and one FDD 4-pin connector. This is a huge amount of connectivity, especially for the 550 watt version and you would be hard pressed to find a similar rated unit with this much support.

Whereas many high-end power supplies now include 8-pin to 6-pin adapters for graphics cards that do not require all eight pins, OCZ has removed the need for such adapters. Rather they have built the adapters right into the cables, meaning that all PCI Express cables can work in both 6-pin and 8-pin connectors.

At the rear of the OCZ ZT series power supplies we have the power input connector along with the power on/off button. Because these are switch power supplies, there is no need to include the option to switch between 110v/230v, which can destroy the power supply if set to the wrong setting.

The rear of the power supply is covered in honeycomb holes which are designed to act as exhaust ventilation. The cool air forced in by the 140mm fan exits through the rear of the power supply and out of the case.

As we understand it the ZT series has been designed and built by Great Wall, just as the ZX series was. That said, it is not a generic OEM design so it should differ to that of other units which are also made by Great Wall.

Having removed the lid from the OCZ ZT power supplies, we were not all that shocked to find that the design of the 650w and 750w units is much the same. Although the design of the 550w unit is essentially the same for the most part, you will notice that there is a heatsink missing.

The internal designs of these power supplies are quite busy, featuring a number of large black aluminum heatsinks. These three heatsinks are positioned directly below the 140mm intake fan. There is a single large Teapo capacitor featured in each power supply, which is rated for 105°C rather than 85°C.

There is a single 140mm fan that is located in the bottom of the power supply. The fan was produced by Yate Loon and is designed to operate at up to 2800-RPM, at which speed it creates quite a lot of noise (48.5dBA) and since the ZT series is whisper quiet we have to think it is spinning much slower.

Finally some technical specifications that are found on the label included on the OCZ ZT series power supplies. For all three units OCZ has gone with a single +12v rail which provides better compatibility for the latest components when compared to a quad rail setup. However, the ratings of these rails obviously vary from unit to unit.

Hardware - Intel Core i7-3960X Extreme Edition (3.30GHz) - x4 2GB G.Skill DDR3-1600(CAS 8-8-8-20) - Crucial m4 512GB (SATA 6Gb/s) - Gigabyte Radeon HD 6970 (2048MB) Crossfire - Gigabyte G1.Assassin2 (Intel X79) Software - Microsoft Windows 7 Ultimate SP1 (64-bit) - Nvidia Forceware 258.96 WHQL

The six-core Core i7 processor has also been overclocked causing it to not only run faster, but also consume considerably more power. The overclock saw the default 3.30GHz operating frequency pushed to a lightning fast 4.0GHz! In addition, a few other devices were plugged in for the ride. These included a total of two 1TB hard drives, four large case fans, a water-cooling system, 8GBs of memory, and a single DVD-RW.

The OCZ ZX 1250w and ZT 750w were tested using a pair of Radeon HD 6970 graphics cards and as you can see the system power consumption exceeded 600 watts. The 1250w unit did use 30 watts less, though overall we were pleased with what the 750w model could handle. The smaller 650w and 550w units only support a single graphics card and as you can see the 550w model was more than capable as we were only drawing 419 watts from the wall here.

Despite being very quiet even when under full load, the OCZ ZT Series remained very cool, as all three units operated at less than 50 degrees. The idle temperatures were also very good and were only a few degrees higher than the ambient room temperature.

The performance of the OCZ ZT series was excellent, as the voltages did not vary greatly when under load. The stress test results were recorded running Prime95 along with Furmark running. Both programs were able to maintain a constant CPU and GPU utilization level of 100% while using various other system devices. Furthermore, a number of the hard drives were being accessed at the same time via other networked computers. This had virtually no impact on the power supply's performance over several hours of hard usage.

At just $110 we found the 750w model to be a very capable power supply and it is easily powerful enough to handle a pair of Radeon HD 6970, or even the new 7970 graphics cards, while also powering the world’s most powerful desktop processor. For those with relatively high-end SLI or Crossfire setups the ZT 750w is certainly the way to go, especially from a value perspective.

The key feature of these power supplies is the 80-Plus Bronze Certification and when compared to the much more expensive ZX 1250w unit which features a Gold Certification, we found the ZT 750w to be surprisingly efficient.

Given that we took the world’s most powerful desktop processor, the Core i7-3960X, and overclocked it to 4GHz while also throwing in a pair of Radeon HD 6970 Crossfire graphics cards, we were impressed that the OCZ ZT 750w was able to tackle this configuration. Keeping in mind we also threw in considerably more hardware as well.

This configuration pushed the 750w unit close to its peak rating, and while it did pass our tests with flying colors, stressing a power supply like this over a much longer period, such as a year, could be fatal. That said, with almost 100 watts of headroom we are confident that the OCZ ZT 750w could power this system without any reliability issues.

The four PCI Express power connectors mean that the OCZ ZX 750w is both CrossfireX and SLI certified, as we had no problem running a pair of GeForce GTX 570 SLI or Radeon HD 6970 Crossfire graphics cards. The single +12v rail certainly helps to improve compatibility when using such extreme graphics card configurations.

As a side note, those wanting to invest in 3-way SLI or CrossfireX will want to check out the bigger and more expensive 1000w and 1250w units from the ZX range which support up to six PCIe 8-pin connectors.

Something we really appreciated about these affordable power supplies was the cable management system, or 100% modular design as it is commonly referred to. This design helps to not only simplify the installation process, but it also makes for a very tidy install, and this is always something that we like to see.

We have been very pleased with the OCZ ZT Series, and believe that they would make a fine addition to any mid-range gaming system. Finally, gamers will be able to invest their hard earned cash in a ZT Series power supply knowing it is backed by a full 5-year OCZ warranty.