by Tim Tscheblockov
09/23/2004 | 09:16 AM
“Pure” and stable powering of all the system components is a fundamental requirement to keeping your computer up and running at its nominal frequencies and, moreover, during overclocking. That’s why, for example, a good power-supply unit means no less for an overclocker than an efficient air cooler or a water-cooling system. I guess you can name the hungriest components of a modern computer yourself. They are the central processor and the graphics card, of course. Obtaining a premium PSU, you can stop bothering about the stability of the power these two devices feed on, but an insufficient “purity” can cause problems, theoretically speaking.
The topic of this review comes from OCZ Technology. I will be talking about special wires that efficiently (so says the manufacturer) suppress electromagnetic interference in power circuitry of modern graphics cards, hard disk drives and other PSU-powered components of your computer. The description of the innovation, taken from the manufacturer’s website, read as follows:
The OCZ Enhanced VGA and HDD Power Lead allows users to eliminate “Snowing” and “Water Wave” effects when plugging into high-end VGA cards and Hard Disk Drives. The OCZ PowerShield EMI Control technology with copper-shielded power leads provides extreme current stabilization and is ideal solution for high-resolution applications such as PC games, video editing, and 3-D graphics design. In addition, OCZ’s PowerShield EMI Control technology substantially reduces inbound and feedback RF interference.
Well, it was years ago with a RADEON 7200 from some obscure manufacturer that I last saw such “snowing and waving” on the screen on my monitor, so I just can’t judge if the “wondrous wires” are of any use in this respect. Anyway, I am going to check out OCZ’s claims at least partially, and assess the efficiency of the Power Lead with an oscilloscope.
The OCZ Enhanced VGA & HDD Power Lead kit consists of two cables:
The cables, as you must have understood, are connected in-line into the power circuits. With one end, they are attached into the standard power connector…
…and their other end plugs into the HDD or the graphics card:
The cables are perfectly identical – a complex contraption, all shielded and isolated:
A few details bulge out from under the isolation near the output connector. I moved the isolation away to see the following:
There are two 10µF/25v electrolytic and two 0.1µF ceramic capacitors soldered between the +5v/+12v contacts and the middle “zero” contacts of the cable. These capacitors and a long ferrite bead, which is located a bit farther from the connector, form an LC filter that suppresses high-frequency interference.
Farther still, behind the ferrite bead, there’s a braided shield visible under the transparent casing. Interestingly, the cable has two shield layers rather than one. The first layer is the braid proper and the second, located beneath the first, is made of metal foil.
The shield would be more efficient if it was connected to a common wire, but it is not as you can see on the snapshot:
On the other hand, I can’t consider this as a serious defect. I even doubt the very necessity of shielding this cable since there are several centimeters of unshielded cable going from the PSU to the OCZ lead. Of course, the shielded cable looks impressive – OCZ takes care of nice looks of its products.
Now, let’s see what good these wondrous wires can do to your computer.
I tested the cables from OCZ Technologies on a testbed with the following configuration:
I attached one OCZ cable to the graphics card’s additional power connector and took the oscillograms with the help of an M621 digital oscilloscope from ETC. I performed the tests in two modes: “Idle” (the Windows Desktop on the screen, 1280x1024@75Hz display mode) and “Burn” (a botmatch running in Unreal Tournament 2004, in 1024x768 resolution, with forced 4x full-screen antialiasing and 8x anisotropic filtering, and at the maximum graphics quality settings).
So, let’s first see how well the cables suppress the noise the graphics card receives from the +5/+12v lines through the additional power connector. In the oscillogram below, the signal in the +12v line on the cable’s input is shown in green and on the output (i.e. on the graphics card’s power connector) in yellow. The unit of the X axis is 1 microsecond, and the unit of the Y axis equals 50 millivolts. This and other oscillograms were taken in the alternating current mode.
As shown, there are current surges in the input signal (green) that repeat each 3 microseconds, i.e. at a frequency of about 300 kHz. This interference is evidently produced by some system component like a CPU voltage regulator. By the way, this interference of the same value is observed both in the +12v line and in the +5v line.
But what about the OCZ cable? The oscillogram shows that the cable does reduce the interference considerably – its swing was about 75mv on the input, but only 20mv on the output. That’s an excellent result. The next oscillogram is taken under the same conditions, but on a different scale: one unit of the X axis now corresponds to 200 microseconds.
It is clear that the interference level is much lower on the output. The same goes for the +5v line, too. The interference is successfully damped by the cable’s LC filter, and there’s no sense in taking more oscillograms.
So, the OCZ cable can handle well the high-frequency noise that comes in with the electric current from the outside. But what if we launch a 3D game? There will appear low-frequency noise generated by the graphics card, rather than coming from the outside. The power consumption of the graphics card is irregular, with peaks following at the frame-rate frequency, i.e. a few dozen hertz.
The oscillogram below is taken in the +12v line in the Burn mode; it shows you the signal in the additional power connector of the graphics card (yellow) and in-between the OCZ cable and the PSU’s power cable (green). The X axis has a unit of 10 milliseconds; the Y axis – of 50mv:
The +12v power rail bottoms out under the graphics card with surges of 100-130mv that come at a period of 22 milliseconds, which corresponds to a frame rate of 45 fps. The cable from OCZ evidently cannot cope with the interference that comes to the power circuitry from the graphics card. The same goes for the +5v power rail. The oscillogram below shows you the signal on the additional power connector of the graphics card (yellow), i.e. between the graphics card and the OCZ cable. Green marks the signal between the OCZ cable and the power cable from the PSU. One unit of the X axis equals 10 milliseconds, and of the Y axis – 50 millivolts:
The filter influences the result here: the interference of the graphics card becomes smaller after it has passed through the OCZ cable. After the game scene changes, the power consumption of the graphics card changes slightly, too, and this can be seen in an oscillogram taken a few seconds after the previous one. The effect of the special cable from OCZ remains the same, though. The level of noise is lower on the output of the cable than on the input, i.e. on the graphics card’s additional power connector.
If we stretch the time scale in 10 thousand times, one unit of the X axis will correspond to 1 microsecond. The low-frequency constituents of the interference won’t be seen in the oscillogram then – the jaggies in the previous oscillograms will stretch out into almost horizontal lines. But high-frequency constituents will be perfectly visible:
The graphics card does not generate high-frequency noise working under a load. You can only see the same surges at a frequency of about 300kHz that come in from the outside and are more or less successfully suppressed by the cable’s filter: green denotes the signal in the place where the OCZ cable and the PSU cable connect, yellow denotes the signal between the OCZ cable and the additional power connector of the graphics card.
So, the filtering cable from OCZ Technology successfully eliminates the high-frequency constituents of the interference that comes to the graphics card along the power lines from the outside. If the graphics card were to produce such noise, the cable would handle it, too, not allowing it to pass from the graphics card to the PSU. As for the low-frequency constituents of the noise that appear when the graphics card is under a load, the OCZ cable cannot eliminate them.
How do you reduce the effect of this interference on other system components like hard disk drives? Very simple – just don’t attach them to the connectors of the same power cable that the graphics card is attached to. Most PSUs have several cables for powering peripherals like HDDs, optical drives and others, so you shouldn’t feel any lack of them.
The oscillogram below shows the signal in the +5v line on the graphics card’s additional power connector in green, and the signal on the connector of other power cable in yellow. The units of the X and Y axes are 10 milliseconds and 50 millivolts, respectively. The graphics card works in the Burn mode:
The noise from the graphics card passes through the PSU and comes to the connectors of the other power cable much weakened. This is no surprise as any normal PSU has high-capacity output capacitors. Now, I take another oscillogram under the same conditions, but having attached the graphics card’s power not directly, but through the OCZ cable.
Attaching the OCZ cable into the graphics card’s power circuitry doesn’t change anything.
The “wondrous cables” from OCZ Technology do work. They do reduce the high-frequency interference that comes to the graphics card from the outside. Clearly, the cables will be as efficient working “the other way”: the interference from the graphics card will be diminished. That’s about all good that I can say on the topic of this small review. If you’ve got “stripes”, “snowflakes” or “waves” on the screen of your monitor due to electromagnetic interference in the graphics card’s power circuitry, these special cables from OCZ may help. Or they may not help. Graphics cards don’t get their power only through the additional power connector, but also through the AGP slot. The AGP slot receives its 3.3v, 5v and 12v voltages directly from the power connector of the mainboard. Of course, you can’t attach filters like the one implemented in the OCZ cable to these circuits.
The low-frequency noise generated by the graphics card in 3D modes is not practically diminished by the OCZ Power Leads. But it is considerably lowered by the PSU and this is one of the reasons why graphic card manufacturers don’t recommend using the same power cable for the graphics card and other system components.
So, the OCZ Enhanced VGA and HDD Power Lead kit looks nice, installs easily, can cause you no harm, and can do some good. Make your choice.