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Home > News > The Math Behind GPU Power Consumption And PSUs

The Math Behind GPU Power Consumption And PSUs

AWG: Cables Everywhere!

You should be able to access decent cables that provide good connections between graphics CARDS and PSU.But what is the optimal cabling?
Problems like this can only be fun for those who use graphics CARDS to consume more than 200W.It also reminds us of the normal dual-8 pin connector for Radeon r9295x2.But is it really so strict that it's dangerous?

What About AWG?

AWG became a more common term in the PC world with the introduction of AMD`s Radeon R9 295X2. But what does it actually mean? In 1857, James Buchanan succeeded Franklin Pierce as president of the United States, Elisha Otis' first elevator was installed and the AWG standard was created.

AWG stands for American Wire Gauge. It's a coding scheme for wire diameter, only used in North America, very inflexible and hasn`t been updated in ages. But AWG remains a quasi-standard, and there`s really no way around it when it comes to this kind of cable. If you enjoy calculating everything for yourself, the following table includes the AWG norms applicable to our PSU discussion.
Diameter (Ø) in mm
Cross Section in mm2
Equivalent mm²
16 1.29 1.305 1.5
18 1.02 0.79 0.75
20 0.81 0.51 0.5

Does AWG 20 Even Make Sense?

Let`s start with the thinnest wires. At a room temperature of 25 degrees Celsius, at an average cable length of 55cm and assuming that the cable won't exceed a temperature of 50 degrees Celsius, even the thinnest AWG 20 cables still carry up to approximately 10A per wire. Three supply lines add up to a respectable 360W, which would be sufficient for an eight-pin connector.

As usual, the devil`s in the details. In this case, the cable temperature is way too high. That`s why an AWG 20 cable should only be considered for PCIe power connectors of up to approximately 150W. A single six-pin or eight-pin graphics card Power Cable would be perfectly fine.

AWG 18: One Size Fits All

Theoretically, AWG 18 should be sufficient for anything between the PSU and graphics card, which is why this size is the most common. A single AWG 18 cable with two eight-pin connectors from a respected PSU vendor driving AMD's Radeon R9 295X2 yielded good results in our trial.

It`s important to pay close attention to the construction of your PSU though, since there can be massive differences between manufacturers and their models. Unfortunately, we've found unserviceable solutions, as you'll soon see. Some makers of cheap PSUs even try to trick their customers with exceptionally thick insulation, resulting in the cable only looking like it has thick wires.

AWG 16: One Cable To Rule Them All

Very few PSUs offer AWG 16, since it's so much more expensive. Using AWG 16 cables is not really necessary, even if they do help to reduce cable temperatures in high-end systems, improving efficiency. AWG 16 is only worth the extra investment if high currents are going to flow through the cables. Of course, those who place big value on aesthetics and would rather forgo the second cable are on the safe side with AWG 16.

What Could Go Wrong?

Let`s take a look at a cable with two eight-pin leads, which should be able to carry 300W (2 x 150W), according to the ATX specification.

pcie 6 pin to dual 6+2 pin connector adapter cable

The additional ground wires come right out of the connector, and the second connector is more of an Extension Cord than anything else, which means that it doesn`t have its own wires. Consequently, this cable consists of just three 12V wires and the ground. At least in theory, the wires do have enough diameter to serve their purpose. But, practically speaking, the pairs of wires twisted together in their connectors are a huge source of potential problems.

pcie 6+2 pin connector

Looking at the interface to the PSU itself is even more interesting. Everything terminates at a single six-pin connector. Even though the power supply's specifications state that this connector is rated at 20A (240W), and the PSU does shut off, just as it should, beyond that number, a pair of eight-pin connectors on the other end suggest 300W. Simply, this isn't possible due to the multi-rail PSU`s OCP, making the cable configuration all bark and no bite. Unfortunately, the kind of problems shown here reappear in many variations with other PSUs and their cables.

pcie 6 pin connector

Good Solutions And Better Solutions

Normally, such a combined cable should at least have a solid eight-pin connector on the PSU.Here's a good example.The manufacturer decided to use the all-black cable for aesthetic research.It doesn't matter to you or me, but manufacturers have a higher failure rate because the cables are difficult to distinguish and identify.

pcie 8 pin connector

Ideally, each PCIe power connector has a single cable.This eliminates all the problems caused by high current and fast load fluctuations.The AWG 16 cable has a pair of 8 pin connectors, at least the eight-pole PSU connector is the highest available in the same category.

pcie 8 pin to 8 pin connector cable

So What If The Cable Gets Warm After All?

This means that manufacturers have some problems with the purity of copper (and your safety).Most of these cables come from recycled materials, and that alone is not a bad thing.However, the PSU manufacturer's internal tests indicate that the use of alloys containing aluminium, magnesium or zinc is a common method of driving down prices.
This line will be vulnerable in this way, which makes the cable less flexible.In this case, the usual security stockpile of AWG 20 is not enough, and the whole thing becomes a gamble.

Just Don`t Use Them Ever Again: Adapter Problems

Graphics card manufacturers keep adapters for convenience, but they should not be used again.They are outdated in terms of GPU promotion and PowerTune technology.Moreover, good psu is available without destroying Banks.

molex to pcie 6 pin connector cableAt the same time, if their products cannot handle the load, PSU manufacturers do not include a second or third type of PCIe Power Cord.The missing connector is usually a weak warning signal, even if the label shows an excellent wattage level.

dual molex to 6 pin connector cable

The dual adapter is just garbage because all the roads will eventually return to the same 12V source.A PSU should not be pushed to provide what it doesn't have.The only exception is the psu from the OEM system, some of which may have sufficient capacity, but no matter which large store assembly system, the corners are cut off.However, these need to be thoroughly studied before use.

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