Build a GPU Mining Rig

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Hardware

Computer hardware consists of physical components that create a computer system or a

Personal Computer (PC). The major computer components are:

CPU

The CPU (central processing unit) is the brain of a computer—the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions.

The CPU is connected to the motherboard through the designated CPU socket. Each generation of CPU has a different placement socket as the CPU requires different physical circuits that interact with it.

In a GPU mining rig or Ethereum mining rig, the CPU doesn’t play an important role as the mining is done by the GPUs and the CPU stays idle most of the time. So, a low-powered and relatively cheap CPU would be adequate.

Tips on buying a CPU for an Ethereum mining rig:

  • The CPU should be low powered and have the minimum TDP1 possible, as the CPU itself consumes power and dissipates heat even when it’s idle. Having a lower TDP  saves some energy and reduces heat generation.
  • CPUs with more than two physical cores are not necessary for mining purposes. Spending money on something that is more powerful than a dual core Intel CPU or a quad core AMD CPU is wasting money.
  • The CPU must be compatible with the chosen motherboard. Usually, selection of the CPU is of least importance on a GPU mining rig.
  • So, the CPU must be purchased after deciding about the motherboard. Always remember in a GPU mining rig, first we decide about the number and model of the GPU; after that we choose the right motherboard, then CPU and then the required PSU.

Motherboard or Mainboard

The motherboard is the main printed circuit board (PCB) of a computer on which all of the internal computer components are installed. Its purpose is to create a communicative platform for all of the computer hardware. A typical computer motherboard has a place for the CPU, RAM and GPU through different designated slots. Storage devices such as SSD, HDD and other drives usually connect through SATA (on most PCs) ports and cables or on new motherboards through a M.2 slot.

We are not concerned in detail with the features and capabilities of a motherboard in a mining rig. There are only two features that are important:

  • The number of available PCIE slots to accommodate the GPUs.
  • The chipset and variation of the motherboard—what type of CPU and RAM can be supported.

Motherboards come in different sizes, but in a GPU mining rig, we usually use a full-size motherboard that has 4 to 6 available PCIE slots2.

Tips on buying a Motherboard for an Ethereum mining rig

  • The more PCIE slots, the better. As the GPUs are connected to the motherboard through PCIE slots, the motherboard must have at least the same number of available PCIE slots as the desired number of GPUs in your system. In a mining rig, even a PCIE X1 works fine and offers enough bandwidth for GPU mining. So, the total number of available PCIE slots is a combination of all the PCIE slots types. Some motherboards have a combination of X16, X8, X4 and X1. It’s always better to get a motherboard that has one or more available PCIE slots more than you require at the moment as this allows you to add more GPUs in the future if you need to.
  • Buy the newest equipment that you can motherboard with DDR4 RAM types

Physical memory or RAM

Random access memory (RAM) is the best-known form of computer memory. The RAM is connected through motherboard memory slots, and it is the computer’s temporary fast working storage place. When a computer loads, and reads a program, all the data are transferred and stored in the memory. The data are then sent to be processed by the CPU and GPU, and after processing, the data are again stored back in the RAM. So, this memory is a temporary buffer that lets data queue there and prepare for the next stage.

In a GPU mining rig, the RAM component is comparatively the least important of the internal components. Usually, 8 GB of memory is enough for a five to six GPU mining rig (although 4 GB may work fine!). The RAM selection should be compatible with the motherboard; mostly use DDR4 RAMs. The speed of the RAM isn’t important at all for mining purposes, so buying a cheaper option is better regardless of speed—1333 MHz and above does the job.

Storage devices, SSD, HDD, DVD drives, …

A data storage device is a device for recording (storing) information (data). In a personal computer, the storage device is where the operating system, program’s data and personal information are stored. The HDD (hard disk drive) has many solid rotating disks that record the data magnetically, and the SSD (solid state drive) contains memory chips and have no moving parts.

In a GPU mining rig, the storage device has two purposes: 1. Providing a running operating system, usually Microsoft Windows, Linux family or Mac OS., and 2. Allowing the mining program to be installed and run. In a network-mining or pool-mining system, a small amount of storage is required. But a solo-mining rig requires a pretty big storage capacity. The Current Blockchain Size of Ethereum is expected to grow by more than 5 GB per month.

Tips on buying a Storage Drive for an Ethereum mining rig

  • Use a small SSD in pool mining. An SSD is more reliable and harder to break as it does not have any moving parts that eventually will wear out. Some of the SSDs can handle up to 700 Terabytes of writing before they die. A good 64 GB or 128 GB SSD, is adequate for an operating system and mining program in a pool-mining application.
  • Use a 1 TB HDD in a solo-mining rig. A reliable 1 TB HDD is more than enough for a mining rig. Furthermore, a 1 TB HDD is usually the minimum capacity that can be bought these days
  • Don’t buy used storage when the rig is important for you! If the storage fails, the mining operation will stop and it will take time to recover the system. This failure is unlike the breakdown of the other components, such as GPUs, PSU, CPU, RAM. Even the motherboard can be replaced rather quickly without a significant loss in operating time. The operating system and mining software are installed on the storage device, and usually there is only one physical drive being used on a mining rig (unlike a server computer which utilizes multiple drives as the backup). So, if the mining rig is running 24/7, or operated remotely without regular supervision, it is vital that you use a reliable and therefore new storage—second-hand HDDs or SDDs should be totally avoided.

GPU or VGA

The GPU (Graphics Processing Unit) is a computer component specialized for display functions. The GPU renders images, animations and videos for the computer’s screen. GPUs are located on plug-in cards and are placed in PCI Express. There are two major producers of video cards or GPUs—Nvidia with about 65% of the discrete GPU-market share, and AMD with 35% of the market. A graphics card is the most important part in a GPU mining rig while all of the hard work and mining tasks are done by the GPU rendering power (unlike a regular desktop or workstation computer in which the CPU is also very active and important).

A mining software or client utilizes 100% of the GPU power and therefore the maximum designed TDP3 of the GPU would be reached. This matter makes the GPU consume its maximum designed electrical energy and consequently dissipates this consumed energy in the form of heat. If the TDP were lower, the electrical power consumption and generated heat would also be lower. However, in a particular generation of GPU (when the manufacturing technology and design are the same), a lower TDP would mean a lower graphical computational power. Two different generations of GPUs may therefore have different TDP design but similar computational power. As the production technology advances and microcontrollers become smaller and more optimized, they require less energy to do the same operation.

Flops and performance per watt

According to Wikipedia “In computing, FLOPS or flops (an acronym for Floating-points Operations Per Second) is a measure of computer performance, useful in fields of scientific calculations that make heavy use of floating-point calculations.” For such cases, it is a more accurate measure than the generic instructions per second so stronger GPUs have higher flops. The best GPUs are those that have high flops ratings with low TDPs. The performance per watt is calculated by dividing the number of flops by the TDP; the higher the resulting number, the higher the efficiency. Indeed, the number of flops does not necessarily represent the real performance of the GPU in a GPU mining client or in a real-world scenario but it

determines the potential of the GPU’s computational power based on the number of chipset transistors and the manufacturer’s design.

As the chips and circuit boards become smaller, they require a lower voltage and power to operate. The process technology is the particular manufacturing method used to make silicon chips, which is measured by how small the transistor is. The size of a manufactured transistor is measured in nanometers.

Cooling design of GPU

GPUs differ in many ways. In a GPU mining rig, the second most important aspect of the GPU after its computational power or FLOPS, is the “cooling design or cooling solution”. A GPU generates a lot of heat, which needs to be dissipated to keep the core chip and components below the design values. In chapter 3, I explain in detail about heat generation and its dissipation and the life of the components. I also discuss in detail cooling designs. Here, I cover them briefly.

GPUs are equipped with two types of coolers or fans: 1. the blower-style or turbine and 2. the open-air style. In the first type, there is a single centrifugal fan usually placed at the end of the card where usually the power connectors are placed. This fan sucks the air inside a shroud and blows it throw a heat sink which is usually connected with the main chipset of GPU, VRMs and memory chips of GPU. The warm air is emitted from the GPU head. In the second type, there are multiple axial fans which blow air downwards to the designated heat sink which is connected to the GPU components, and the warmed air is exhausted to the surroundings, usually inside the computer case.

Tips on buying a GPU for a mining rig

  • GPUs with 3 GB RAM or more. At the moment, Ethereum mining clients require more than 2 GB of available memory in the GPU. GPUs with 2 GB can’t mine directly and would need to be modified on the client, but eventually the amount of memory will not be enough. Thus, the DAG started at 1 GB at the time of the Frontier launch, and increased by approximately 0.73 times per year. The size is therefore roughly 1.35
  • Always buy a GPU with an open-air design.
  • Buy a GPU with a backplate. As of today, the price of a card with or without the backplate are very similar. A backplate offers extra protection, rigidity and heat dissipation options.
  • Always buy the same model and same brand of a GPU for a mining rig. Donot mix different brands. In my experience, controlling the frequency and fan speed using software like “MSI after Burner”, results in crashes or freezing of the system4.
  • Be on the lookout for local sales and special offers. From time to time,graphics cards are sold at a discounted price online, but unfortunately most of the offers are in the USA.

Input devices, including keyboard, mouse, scanner, etc.

A mining rig requires a mouse and keyboard for the initial setup and, later on, in order to undertake updates and maintenance. However, on a remotely controlled system, a mouse and keyboard aren’t necessary, but as they cost virtually nothing and consume less than a watt of power, it does not matter if they are connected to a remotely controlled system.

Display monitor

As with the keyboard and mouse, a monitor is required to set up the mining rig and to do on-site maintenance and upgrades. However, a 20” LED or LCD monitor can consume up to 30 watthours, so when it is not necessary, monitors should be switched off manually. They should not however be put into sleep mode as this may interfere with mining operations. Often the mining system is set to remain awake and use 100% of the system’s resources, so setting a sleep time for hard drives or monitors is not recommended.

Output devices including printer, speaker, etc.

An Ethereum mining system does not require an extra output device such as a printer or speaker, unless it is being used as a daily computer too.

Computer Case

This is the enclosure that contains the computer components. It excludes the input and output devices such as the monitor, speaker, mouse and keyboard. The computer case is made of metal, plastics or any other material that is rigid enough to hold the components and offer enough protection. You will need to remember in a professional GPU mining rig that usually the computer chassis has an open-air design unlike the typical closed-air system of a normal computer case. I explain in detail in Chapter 5 how to build a GPU mining rig.

The computer case has several functions:

  1. Holding the components and keeping them secure. Computer components are placed in a computer case, which holds them together and provides a rigid base to keep them secure. The motherboard and internal computer components usually have bare electronic parts that should not be touched.
  2. Cooling of the hardware. The electrical energy used by the computer eventually finishes up as heat. So, when a computer uses 1000 watthours of electricity, it would generate 1000 watthours of heat. The generated heat is dissipated by cooling fans which usually are placed inside the computer case. In addition, the case directs the path of the airstream.
  • Appearance of the computer system. For many computer enthusiasts, the appearance of the computer plays a significant role, as is the case with cars.
  • Filtering the dust. Most modern computer cases are equipped with cleanable dust filters right in front of the intake fan. Keeping the components of the computer clean, helps to prolong the life of the moving parts like the GPU

fan and case-cooling fans. Accumulated dirt and dust between the heat sink fins of the CPU, GPU and PSU can affect their cooling.

Tips on buying a computer case for a mining rig

  • Most of the well-built GPU mining rigs with five or six GPUs use open-air design as the case or chassis, see Chapter 5 to learn more about this.
  • Use a quiet intake fan. As your system runs 24/7, if the mining rig in notplaced in an isolated area. Some of the original case fans are noisy when they run at high speed. Pay extra attention to the fans that are already installed in the case, if you have decided not to replace the original case fans.
  • A dust filter is a must. As said earlier, most computer cases are equippedwith dust filters. For a system that runs all the time, dust is an enemy of a GPU mining rig. The dusts filter should be placed on the intake path, and be easily removed and cleaned.
  • The bigger, the better. Usually a mining rig with up to four GPUs, can bebuilt into a computer case, but this is not ideal for more than two GPUs. Why? Because 1. an ordinary computer case is not designed to accommodate so many GPUs, 2. heat dissipation would be troublesome as the GPUs will be placed tightly together, and 3. maintenance and changes are more difficult to undertake in a confined space.

Power Supply Unit (PSU)

A power supply unit (or PSU) converts the mains AC electricity (alternative current) to a low-voltage regulated DC power supply for the internal components of a computer. The most modern desktop personal computer power supplies conform to the ATX6 specification, which covers both the form factor (shape and size of the PSU) and voltage tolerances. While an ATX power supply is connected to the mains supply, it always provides a 5-volt standby (5VSB) voltage so that the standby functions on the computer and certain peripherals are powered. ATX power supplies are turned on and off by a signal from the motherboard. They also provide a signal to the motherboard to indicate when the DC voltages are within specification, so that the computer is able to safely power up and boot.

Many ATX PSUs which are available to buy, do comply with the ATX standard,

What are the main factors of a PSU that a Ethereum mining rig builder should pay attention to?

The output power.

This is the most important factor of a PSU for a miningrig. It should be able to supply enough power to the GPUs. How much power do you need? This is mainly dependent on the number of GPUs that do the mining. Almost every PSU manufactures has a “Power Supply Calculator” page that helps you to choose a suitable PSU for your job, See the following websites: Cooler Master, Be Quiet!, Outer Vision  or Corsair PSU Finder. However, the easiest way is to calculate the required power of your PSU for a modern new Ethereum rig as follow:

  • Minimum PSU requirement: 150 watts multiplied by the number of GPUs
  • Recommended PSU requirement: 200 watts multiplied by the number of GPUs

Number of PCIE power connectors. As a PCIE power connector is required to supply power to the GPU, a mining rig needs special attention. Based on the GPU selection, each GPU may require different power requirement, and a different number of PCIE connectors with 6 or 8 pins of power lines.

Efficiency and ATX standards. Most PSUs are certified to 80 PLUS and IntelATX standards. The 80 PLUS® performance specification requires power supplies for computers and servers to have 80% or greater energy efficiency at 10, 20, 50 and 100% of the rated load with a true power factor of 0.9 or higher. When a 1000 W power supply complies with 80 Plus, it would take 1250 W of electricity to provide the required 1000 W (i.e. 80% of 1250 W), but a 1000 W PSU which complies with 80 Plus Gold requires 1150 W. In a mining rig, usually the PSU operates between 85–95% of the load all the time, so the efficiency at 100 % load is the most important factor to consider.

Table 1 – This table shows the comparison between different 80 standards of the PSU. The most important column to be watched on a GPU mining rig is the efficiency above 80% utilization of the PSU. This would always work in a mining rig.

Efficiency level certifications

80 Plus 10% 20% 50% 100% 10% 20% 50% 100% 10% 20% 50% 100%  
  80% 80% 80%           82% 85% 82%  
80 Plus Bronze   82% 85% 82%   81% 85% 81%   85% 88% 85%  
80 Plus Silver   85% 88% 85%   85% 89% 85%   87% 90% 87%  
80 Plus Gold   87% 90% 87%   88% 92% 88%   90% 92% 89%  
80 Plus Platinum   90% 92% 89%   90% 94% 91%   92% 94% 90%  
80 Plus Titanium 90% 92% 94% 90% 90% 94% 96% 91% 90% 94% 96% 94%  
                       

As mentioned earlier, the current Intel ATX standard is 2.4.

Noise from the PSU. During operation, the PSU also generates heat. Forinstance, the energy lost by a 1000 W, 80 Plus Gold PSU is 150 W and the resulting heat needs to be dissipated. In a mining rig, as the PSU runs at its maximum utilization most of the time, the cooling fans of the PSU also run at their maximum speed. Some PSU fans are very noisy when they run at maximum speed, and this needs to be taken into account if the generated noise of the mining rig is an important consideration. Most manufacturers offer some information about the maximum noise levels of their PSUs with their product information details.

However, in a big mining farm with so many open-air systems, the noise from the PSUs is generally swamped by the noise of the GPUs (see chapter 5).

Cooling Fans

Fans or computer fans are used for active cooling. Active cooling of a computer usually involves transferring heat to air, water or other liquids, and moving the heated medium to outside of the case. If a particular component doesn’t generate too much heat, passive cooling can be used. For instance, most motherboard VRMs, chipsets and RAMs use passive cooling systems.

Types and main design

Most computers fans are Axial fans. An axial fan increases the pressure of the air flowing through it. The blades of the axial flow fans force air to move parallel to the shaft of the blades.

The other type of computer fan is the centrifugal type, often called blowers. The pressure of an incoming air stream is increased by a fan wheel, a series of blades mounted on a circular hub. Centrifugal fans move air radially, the direction of the outward flowing air is changed; it is usually at 90° to the direction of the incoming air. These types are commonly used in GPUs, laptops and compact desktop machines, all-in-one computers, printers, projectors, etc. where there is not enough space for air movement within the casing of the components.

Features of a computer fan (only axial)

  • Size. The standard computer fan sizes are 80, 90, 120, 140 and 200 millimeters.The most common size is 120 mm. However, in a GPU mining rig with five or six GPUs, computer fans alone don’t provide enough airflow, and the mining rig requires additional fans.
  • PWM or non-PWM. Pulse-width modulation (PWM) is a common method of controlling computer fans. A PWM-capable fan is usually connected to a 4-pin connector (pinout: ground, +12 V, sense output from fan and control input). Non-PWM fans have 3-pin connectors and usually they are called “computer case fan” while they run only at a constant speed. Although even non-PWM fans can be controlled by altering the 12 V DC input using a fan controller or motherboard, not all motherboards are capable of altering the fan voltage. For

instance, a motherboard cannot deliver 10 V to a fan header as it can only deliver a total of 12 V.

  • Noise. Noise is inevitably created by the contact of the fan blades with air.Usually, the maximum noise level of a fan is mentioned in the product data sheet in terms of decibels or sones.
  • Bearing type. A computer fan consists of fan blades, a hub, an electromotor andbearings. There are many different designs of bearing—ball bearings, sliding bearings, hydro-pressure bearings, magnetic levitated bearings and so on. Bearing design has a direct effect on the life of the fan and noise which is generated by the fan.
  • Airflow and static pressure. Airflow fans are those that have high airflows (highCFM) when there is little or no restriction. In a computer case, intake and exhaust fans are usually airflow fans. Static pressure fans offer good airflow when there is an obstacle such as radiator or dust filter restricting the flow.

Airflow fans tend to have a larger number and thinner blades than pressure fans. These are the right type of fans for a GPU mining, when there is no radiator or restricted closed-case chassis as is the case in most GPU mining rigs.

RPM (Revolutions per minute) and relative power. One of the most understandable features of any fan is its RPM; how fast a fan rotates indicates other characteristics. For a particular fan, when the RPM is increased, the air pressure or flow and the noise increase. However, this is not necessarily the case with different fans—a higher RPM fan does not necessarily result in a higher airflow or noise. Some fans rotate at relatively low RPMs and produce a high airflow because of having a larger number of larger blades. Increasing the airflow of a particular fan requires more power.

Tips on buying a computer fan for a mining rig

In a GPU mining rig, we should use airflow rather than static pressure fans.

If noise isn’t a problem, the recommended fans are those which have higher CFMs and operate up to 4000 RPM.

Never connect a high-RPM & high-wattage fan to a motherboard fan header, as it may damage the motherboard because of the high-power drain. Always use a fan controller that can provide up to 3 amps to a fan header.

You will require an extra 100–150 CFM for each GPU of your open-air mining rig.

A cooling solution with 120 mm high-RPM computer fans and a fan controller generally costs less than an industrial solution.