Basics GPUs Pro PSU Reviews

Basics GPUs: Power Consumption, Power Supply Conflicts & Other Myths | 2014 and 2020

Some consideration instead of panic always helps

Between the graphics card and the power supply, more or less functionally designed and connected cables ensure a hopefully good connection. But what are the limits and what does optimal cabling look like? Of course, this question only becomes really interesting after power recordings above 200 watts per graphics card. And here again we remember the discussions about the two 8-pin connections of the R9 295X2, which are far from any standards. But are these standards really so narrow that crossing immediately becomes a danger?

AWG what?

At least since AMD's Radeon R9 295X2 the term AWG is on everyone's mouth. But what is behind it? Sepp Moser invented the Weißwurst in Munich on Rose Monday in 1857, in the same year the powder tower explodes in the fortress Mainz – and the AWG is founded in North America. AWG stands for American Wire Gauge and is a coding for wire diameter. Even though this standard is mainly used in North America, is inflexible and has not been adapted forever – it is a kind of quasi-standard that you can hardly get past with such cables. For the very curious and self-calculator, the table with the respective AWG standards, which are relevant for us for power supplies:

AWG number Diameter (A) in mm Cross-section in mm2 Equivalent mm2
(metric)
16 1,29 1,305 1.5
18 1.02 0,79 0.75
20 0.81 0,51 0,5

Does AWG 20 make any sense at all?

Let's start with the thinnest lines. For example, if the room temperature is 25 °C and one wanted to live with an average cable length of 55 cm with a maximum of 50 °C cable temperature, then even with the thinner AWG-20 cables, there would still be about approx. 10 amps per line doable. This would result in 360 watts with three discharged lines, which could even be enough for an 8-pin connection. But the devil is always in the detail and already this temperature is clearly too high. Therefore, AWG-20 cables should only be considered for power up to approximately 150 watts when connecting to PCI Express. A single 6-pin or 8-pin cable for powering a graphics card would be perfectly fine.

AWG 18: One for everything

Theoretically, AWG 18 could already cover everything that is necessary for cabling between the power supply and the graphics card. That's why this size is also the most widely used. A single AWG-18 cable of a branded power supply with two 8-pin connectors connected to the R9 295X2 passed this test with flying colours. In the end, one only has to pay attention to the exact execution, because there are major differences between the power supply manufacturers and their models and, unfortunately, also inappropriate solutions, as we shall see in a short time. In addition, some cheapest suppliers also trick with particularly thick insulation, which then only imagines the thick lines – so you can also fall in.

AWG 16: The Royal Class

Only a few power supplies offer AWG 16, because the financial commitment of the supplier is also highest. The use of AWG-16 cables is not mandatory, but it significantly lowers cable temperatures in high-end systems and also helps to increase efficiency. However, AWG 16 is only worthwhile if really high currents are to flow. If you value optics and want to save the second cable on graphics cards with two power connections, a wg16 is of course still on the sunny side.

What can go wrong

Let's take a look at the 2x 8-pin cable of a power supply that is no longer available, which according to the ATX specification should be loaded with 300 watts (2x 150 watts):

 

However, the two additional ground lines are retrieved from the plug itself and the second plug is only a kind of extension, so it does not use its own cables. Thus, this connection cable consists of only three cables for 12 volts and ground. Theoretically, one manages it with the cable cross-section, which should be sufficient for this, but the only twisted double cables in the plugs are already a nasty fault devil.

 

The connection to the power supply itself becomes even more interesting with this cable, because here everything ends in a single 6-pin plug. Although the power supply shows this connection in the data battwith 20 amps (240 watts) (and also switches off nicely), the two 8-pin connections suggest 300 watts. This cannot work at all due to the OCP of the multi-rail power supply. Full of blenders.

It is better to refrain from such power supplies and cables and the failure shown here can be seen again and again in many variations.

Good and better solutions

Normally, these combined cables should have at least one solid 8-pin connector on the power supply. A good example shows the following figure, in which, for optical reasons, one has bet on completely black lines (which is not relevant for the end customer, but already leads to higher scrap rates with the manufacturer due to lack of clarity):

The ideal state would actually be separate cables, i.e. a separate cable for each PCI Express connection. This is a pretty elegant way to avoid any annoyances that can occur at such high currents and fast load changes. Combined AWG-16 cables with 2x 8 pins and at least 8-pin power plugs, which are very easy to use, fall into the same category.

And when the cable gets warm?

 

Then the manufacturer has cheated a little and plays with contaminated copper as well as the safety of customers. Most of the copper for such cables comes from recycled raw materials, which in itself is not a bad thing – on the contrary. Internal tests at power supply suppliers have shown, however, that some price pushers sometimes like to use alloys that have a certain aluminium, magnesium or zinc content. The strands are then sometimes very brittle and the cables not particularly flexible. In such cases, the actual safety reserve of AWG 20 is no longer sufficient and it becomes pure gambling.

Please no longer use: Adapter Murks

Even if the graphics card manufacturers repeatedly enclose such unspeakable adapters – their use is simply no longer up-to-date in the age of modern graphics cards with Boost or Power Tune, especially since good and sufficient power supplies are also cheap to purchase.

 

On the contrary, the power supply providers usually omit the second or third PCI Express cable whenever the power supply does not come to terms with the performance of the power supply. Missing connections are therefore always a direct warning of a lack of performance, even if the label has a great performance specification!

 

Such double adapters are nonsense, because in the end everything only amounts to a single 12-volt source. What the power supply cannot do should not be forced behind. The only exception is system builder power supplies from OEM computers, where the performance would theoretically be there, but the assembler saved on the original device. However, a thorough review of the circumstances must be carried out before such a thing is used.

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About the author

Igor Wallossek

Editor-in-chief and name-giver of igor'sLAB as the content successor of Tom's Hardware Germany, whose license was returned in June 2019 in order to better meet the qualitative demands of web content and challenges of new media such as YouTube with its own channel.

Computer nerd since 1983, audio freak since 1979 and pretty much open to anything with a plug or battery for over 50 years.

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