Breaking News

OCZ ZT Series 650W Power Supply (OCZ-ZS650W)

Available in 550W, 650W and 750W, the latest ZT model PSU from OCZ is targeted toward enthusiasts and main-users. We put the 650W unit to the test to see how well it performs.



OCZ is renowned as one of the most successful players in the SSD industry. However, OCZ also makes power supplies. The memory giant acquired PC Power & Cooling back in 2007. Often considered one of the best PSU brands by enthusiasts, the PC Power & Cooling branded PSU is the IT poster boy when choosing a power supply.

OCZ’s latest ZT Series power supply is designed to satisfy mainstream users who want high-performance, solid and reliable PSU. The unit is fully modular cable design with 80-Plus Bronze certification, available in 550W, 650W, and 750W. Regardless of which model you choose, the PSU features a single +12V rail with 140mm ball-bearing fan designed to deliver highest power with minimal noise. We have here the 650W (OCZ-ZT650W) that we will put through our test.

650W ZT Series

The retail box for the ZT is attractive with a black and yellow color scheme. The power supply is a high-performance power supply with 100% modular cables. On the back, we see that OCZ advertises the unit as “Extreme Cool” with a 140mm fan and 80-Plus Bronze certification. This signifies that the PSU delivers up to 85% efficiency under typical load. The unit also comes with 5-year warranty. The best part is that it comes with a “PowerSwap” program where OCZ will ship a replacement unit before users send in the defective unit.

On the back is where users will see the PSU’s specification and ratings for the rails. What we can notice here is that the PSU is rated continuously at 45°C and is build with low ESR 105°C electrolytic capacitors. The fact that the PSU is rated at 45°C will ensure that it provides rated power under typical operating environment. 

The unit is built with a single +12V rail with rated 54A. This works out to be a maximum 648 watts of dedicated power for all important +12V rail. The +3.3V rail has a rating of 30A and the +5V is rated with 24A. The combined +5V and +3.3V has a maximum 170 watts of power.

Inside of the box, we see the ZT is packaged very well where the accessories and the cables are placed in a separate compartment and the PSU is placed inside a bag to prevent scratches. The bag can be used to keep unused cables after you take out the PSU.

The following cables are included:

  • 1x 24+4 power cable
  • 1x 4+4 CPU +12V auxiliary power cable
  • 2x 6+2 PCI Express power cable
  • 3x SATA power cable (3 connectors/cable, total of 9 SATA connectors)
  • 2x molex cable (3 connectors/cable, total of 6 molex connectors)
  • 1x FDD (with the included adapter)

Rather than having a dedicated FDD connector attached to the molex cable, OCZ provides an adapter that converts one of the molex to FDD. This is a good idea as many people are not using the FDD power connector anymore. All of the cables are fully sleeved and OCZ includes flat SATA cables for better cable management and air flow.

The included SATA and molex cables are a little short. From the main power supply to the first connector is about 38 cm and there is about 15 cm between each connector. The PCI-E power cable and the 8-pin auxiliary ATX power cables are about 57cm long and the main ATX power cable is about 54 cm long. With a growing trend of bottom mounting PSU, the short auxiliary ATX power connector will most likely going to be too short for full-tower or mid-ATX cases that accommodates EATX form factor motherboards with the auxiliary power connector placed on the upper edge of the board.

The connectors on the power supply are clearly labeled and color coded for easy installation. Except for the peripheral/IDE/SATA connectors, there are plenty of space to easily access the connectors. The peripheral/IDE/SATA connectors are lined up in such a way that the secure tabs holding the connector to the port are facing inward, which makes it harder to reach the tab. It would much easier if these connectors were facing upward or downward like the PCI-E ports for easy access.

The back of the PSU has the usual power switch and a very large opening for ventilation. We can see the honeycomb grill covers almost the area on the back.

Printed on the PSU is the specification of the PS as well as its certifications.

A single large 140mm fan is located on the bottom of the PSU to keep the internal components cool.

Understanding PSU RAILS

We have all no doubt been told when purchasing a power supply, that the number to look for is the amps on the 12V rail. What are each of the different rails for though, and why is the 12V rail typically the most important? Why the heck are they called rails? Let’s take at look at each and see.

-12V – This rail is pretty much obsolete now and is only kept on to provide backward compatibility with older hardware. Some older types of serial port circuits required both -12V and +12V voltages, but since almost no one except industrial users use serial ports anymore you as a typical home user can pretty much disregard this rail.

-5V – Again this is another obsolete rail, the -5V was used for old school floppy controllers and some ISA bus cards. Again, no need for the typical home user to worry about this rail.

0V – Though not listed on any manufacturer spec sheet, every power supply has a 0V ground line. The ground signal is used to complete circuits with other voltages and provide a plane of reference against which other voltages are measured.

+3.3V – Finally we are starting to get into something useful! The +3.3V rail was introduced with the ATX form factor in order to power second generation Pentium chips. Previously the CPU was powered by the +5V rail (along with the system memory and everything else on the motherboard), but a reduced voltage was needed in order to reduce power consumption as the chips got faster.

+5V – As mentioned above, the +5V used to run the motherboard, CPU and the majority of other system components on older pre ATX based systems. On newer systems, many of the components have migrated to either the +3.3V or +12V rails, but the motherboard and many of its onboard components still use the +5V rail so it is of importance to the typical home user.

+5V SB – The +5V Standby or “Soft Power” signal carries the same output level as the +5V rail but is independent and is always on, even when the computer is turned off. This rail allows for two things. First, it allows the motherboard to control the power supply when it is off by enabling features such as wake up from sleep mode, or wake on LAN technology to function. It also is what allows Windows to turn your computer off automatically on shutdown as opposed to previous AT supplies where you had to bend over and push the button. Every standard ATX power supply on the market will include this rail.

+ 12V – The +12V, also known as the mother of all rails, is now used to power the most demanding components in your system including the CPU, hard drives, cooling fans, and graphics cards. Historically the +12V rail was used only to power drives and cooling fans. With the introduction of the 4-pin CPU plug on P4 motherboards and then eventually AMD based motherboards, in order to supply newer power hungry CPUs, the +12V rail suddenly started to grow in importance. Today, multi core based motherboards require an 8-pin +12V connector to supply their power needs. High end GPU cards have also jumped on the +12V rail, which has required PSU makers to adapt. Where previously there was only a single +12V rail, there are now two or more, each designated to power specific devices in order to ensure that nothing is underpowered.


We strive best to load each power supply with the components and power demands that a potential buyer will use.  For this particular power supply, we will be installing these following components at the given condition:

  • Intel Core i5 2500K
  • ASUS P8Z68-V Pro
  • 2x2GB Kingston HyperX 1600MHz
  • Two HD 6950 in CrossFire
  • ThermalRight XI-128 with Scythe S-FLEX SFF21F
  • DVDRW: NEC 3520AW
  • CoolIT Freezone and CoolIT Eliminator
  • Various peripherals that includes PS/2 keyboard, USB mouse, and other USB devices and storage.

We tested the OCZ ZT 650W PSU at five different consumption ranges from 196W to the maximum load of 650W. The wattage reading of each rail will be carried out with the Kill-A-Watt P4400. We monitored the stability of each rail with a multimeter. The test system is connected to a UPS to reduce any power spikes.


Power Output Results(V)

Power Consumption (W) 196W 261 W 326 W 400W 650W
3.3v 3.44 3.43 3.43 3.43 3.26
5v 5.03 5.03 5.02 5.02 4.87
12v 12.27 12.27 12.25 12.24 11.93

For power supplies, industry standards are 5% variance on any rail maximum, which is a little more lax than our standard of 3% max variance. The +3.3V, +5.0V, and the +12V are within the industry standard, though not always within our 3% standard. Even under full load, the PSU is still within the tolerance level and just slightly under the specified voltage.

Let’s take a look voltage stability.

The +3.3V rail fluctuates between 3.35V and 3.39V when the system switches from idle to load. When the system is under a prolonged period of idle or load, it is rock solid and not much fluctuation is detected.

The +5V fluctuates between 4.96V and 5.04V. There is about 0.04V of fluctuation when the system is under a prolonged period of load or idle. In fact, we can see the +5V fluctuates the most when the system is under load.

The +12V fluctuates between 11.9V and 12.2V when the system switches from load to idle. Under load, there is a slight fluctuation of 0.1V initially but it stabilized afterwards.

Noise level

In terms of noise level, the ZT is very quiet up to 400W of power consumption. When it is stressed to 650W, the noise from the fan is definitely audible but not too loud to the point that it becomes an annoyance. Unless users are seeking an absolutely quiet system even under full-load, we doubt people would be bothered by the noise level of the PSU.


The first power supply from the OCZ ZT series designed for mainstream users is a solid unit. The unit has a solid built with attractive exterior and good mix of cables. Users should enjoy the fully modular cable design for better air flow and cable management.
The PSU performs decently. Under full load, we see 0.34V drop on the +12V rail and 0.16V drop on the +3.3V and +5V rails. However, the +5V rail shows constant fluctuation under load and +12V rail also shows slight fluctuation. While we would prefer to have a PSU with slightly less fluctuation, the ZT nonetheless still offers a good strong voltage under under full load.
Certainly, the 650W unit is not designed for enthusiasts with its lack of second additional auxiliary ATX power connector, and additional PCI-E power cable. For mainstream user who need a PSU for single GPU configuration, the OCZ ZT is definitely worth checking out. The unit comes with 5 year warranty and OCZ’s PowerSwap replacement program, ensuring minimal system downtime.
Performance 8
Value 8
Quality 9
Features 9
Innovation 7
We are using a new addition to our scoring system to provide additional feedback beyond a flat score. Please note that the final score isn’t an aggregate average of the new rating system.
Total 8.5
Pros Cons
Fully modular80+ Bronze

Good price to performance ratio

5 year warranty with “PowerSwap” program


Slightly more expensiveCable is a bit short

Slight fluctuation with +5V and +12V under load.

Higher efficiency would be appreciated



Summary: At $99.99, the OCZ 650W ZT PSU is slightly more expensive than the competitor. However, it offers the mainstream users a good mixture of cables with a single +12V rail of 54A, enough to power up any system with a single high-end GPU. It earns the Bjorn3D Seal of Approval.


Check Also

Fifine Ampligame A6T

Introduction Much like the webcam, the USB microphone has become a rather indispensable tool in …

Cooler Master Hyper 622 Halo

Introduction The liquid cooling is the go to cooler for the PC enthusiasts who want …

Leave a Reply

instagram default popup image round
Follow Me
502k 100k 3 month ago