Due to the demand for GPU mining rigs for cryptocurrency generation that are capable of powering more than 2 video cards (what is normally enough for gaming needs) some motherboard manufacturers have come up with specialized products especially for GPU mining needs. One such brand is AsRock that already has two specialized motherboards designed for GPU mining rigs and though the company uses Bitcoin mining all over these products, they are essentially for Litecoin and other scrypt-based alternative cryptos. Nowadays there is no more point in mining for Bitcoin with GPUs, you need to use specialized Bitcoin mining ASIC devices (for other SHA-256 cryptos as well), however scrypt mining and Litecoin in particular is still mineable with GPU. And a lot of people are still building new GPU mining righs with multiple video cards for mining Litecoin, so AsRock’s products can be ideal for these needs.
AsRock offers 2 models of specialized GPU mining rig motherboards, one is the cheaper AsRock H61 Pro BTC, designed for Intel Socket 1155 processors and the other one is AsRock H81 Pro BTC, designed for use with Intel Socket 1150 CPUs. Other than the use of different processors these two motherboards are pretty similar in what they offer – support for up to 6 video cards, though you will need to also use PCI-E x1 extenders to attach all of the video cards to the motherboard and you will also need a special rig designed to contain the 6 video cards. These motherboard also have additional 4-pin molex connectors that you need to connect in order for the motherboard to supply enough power to the video cards over the PCI-E slots.
Also if you plan on using all 6 PCI-E slots with GPUs you may need to be careful what OS you are going to be using in order for the operating system to be able to see and use all of the cards at the same time. Linux is a good option for 6 cards at the same time, and there are specialized Linux distributions available for mining rigs. The problem with Linux however is that the control of voltage of the GPUs may not work with all video cards, in fact with most you my have trouble changing the voltage of the GPU, though the clock frequencies are accessible and you can change them for better performance and higher hashrate. So also do have that in mind when building a 