Graphics cards with AMD's RX 500 and Vega series and Nvidia's GeForce GTX 10 GPUs have been sold out for months (almost) and are also very expensive. The reason? They are bought on a massive scale to mine cryptocoins such as Ethereum and Zcash. Not a nice development for gamers, but unfortunately a fact we can't ignore. It's time for us to find out which GPUs perform best in mining.
Home mining: current PC or new mining rig?
If you want to start mining, you can do so in two ways. The simplest method is to use a video card that you already have at times when you are not actively using it. A gaming PC that is really only used a few hours a day, you can of course use the rest of the time to mine. If that's the case, and you don't have to recoup the investment of the video card, it's especially important to look at the energy consumption of your PC. In the Netherlands, energy is paid for at a price of around 20 eurocents per kilowatt hour. As a result, older CPUs quickly consume more energy than they generate in terms of mining. However, with modern video cards from AMD's RX 400 and 500 series and Nvidia's GeForce 10 models, you can still mine profitably.
Another, financially more risky way is to build a dedicated mining rig with multiple video cards. From an efficiency point of view, the most interesting thing is to mine with multiple CPUs in one system. Besides the graphics card that does the actual mining, you always have other components such as processor, motherboard, memory and SSD or hard disk that also consume energy but do not contribute to the yield. The more graphics cards you can place in one system, the lower this energy overhead of the other components will be.
However, it is not easy to have large quantities of video cards working together in one system. On most motherboards you can often only physically store two or three video cards, and in most cases the cards will be placed very close to each other. This is not ideal: a mining system will usually work 24 hours per maximum workload (approximately). Problems with heat dissipation are therefore on the horizon.
This problem can be solved quite easily with so-called PCI-Express risers. For mining, usually models are used with a PCI-Express x16 slot placed on a circuit board that is powered by a SATA or Molex plug, and is connected by a USB cable to a small circuit board with a PCI-Express X1 connector that can be plugged into any motherboard. Although these risers use USB cables, it is a pure PCI Express X1 signal that is 'extended' in this way. Now you might think that a PCI Express X1 slot doesn't provide enough bandwidth for a modern video card, and to play games that's certainly the case. However, when cryptocoins are mined, no high demands are placed on the bus. In fact, each time a short command is sent to the GPU, which is then calculated locally on the card and the result is returned to the computer. So by using risers it is possible - in theory - to use any PCI Express slot on the motherboard to connect a video card. In theory, because in practice not every motherboard is actually able to control more than five video cards.
Risers allow you to connect more video cards to a motherboard than would normally be possible. Another advantage is that you can place the cards further apart from each other. By making a frame out of wood or aluminium with at least ten centimetres between the cards, the heat dissipation will be much better.
Mining rigs, systems with several video cards that are connected via risers, are mostly self-developed projects, for which frames are made out of wood or aluminium by which the video cards are placed relatively far apart.
It is clear that building a mining rig with several graphics cards requires considerable financial investment. Certainly with the current prices of video cards you can easily spend thousands of euros for a rig with six or more cards, and with the strongly fluctuating crypto prices the question is how quickly you will earn back that investment. In addition, with the arrival of new generations of video cards, existing rigs will quickly become unprofitable, and on top of that the possible sales value of the cards would collapse then.