Mining involves the use of several devices that perform calculations independently of each other and are arranged on one motherboard. In this case, the power supply for mining must have the appropriate power, which will allow powering all devices. A good option would be to use power supplies with high power, but not all of them can be used when assembling a mining farm. This is due to the fact that under normal conditions several video cards are not used, so power supply manufacturers did not provide a large number of similar outputs, and the power provided by the motherboard is also limited.
Even using motherboards designed specifically for mining does not guarantee sufficient power for each mining device. When mining on 6 video cards, the power supply must have a sufficient number of 6 pin or 6 pin+2 outputs, have a reserve of at least 10% above the maximum power consumed by all devices, and be reliable enough to operate around the clock. It is possible to use splitters that provide connection of several devices to one output, but in this case the load on it increases significantly and can lead to failure of the entire power supply.
Power supplies synchronize when video cards do not have enough power
In general, for a farm it is optimal to use a server power supply, but there is always room for an ATX-PSU. We talked about [how to choose the right ATX and server power supplies in a separate article]. Here we'll dive a little deeper into the topic of why power supplies sync and why.
The power supply, no matter how cool it may be, is limited in power and the number of PCI-E connectors. Let's try to figure out why the blocks lack power, but in simple terms.
One power supply can support no more than four video cards.
Roughly speaking, the power supply has a maximum load level on each of the power lines. Based on the intended use of the power line, it has limitations in current strength and conductivity.
Power supplies have separate limits on their power lines.
In the photo, the power supply has a limit of 850 watts per 12V power line.
In fact, these 850 watts are divided between Molex connections, the processor and video cards. The limit for a 3.3V line is 150 W, but this is a common limit together with a 5V line. Lines 3V and 5V are not power
connections; they are not designed to power video cards.
The power supply is not designed for more than 4 video cards.
For example, there are 8 1080 Ti video cards spinning in the rack. One card consumes 250 W. With a simple calculation, we find that 8 cards will consume 2000 W per hour from the 12V line alone. This is a lot for one power supply unit; ATX-power supply units are not produced with such power in mind.
The more video cards, the higher the load on the power supply hardware.
There are many models on the market that can output 2000W, that's true. The problem is different - home ATX power supplies are not suitable for running 8 video cards at once. The maximum that a modern ATX power supply is designed for is 3-4 video cards. This can be seen from the number of PCI-E connections and the limitation on the 12V line.
The risk of the power supply burning out increases with each connected video card.
They have one or two 12V lines that are shared between all PCI-E connectors. To provide the farm with power, paired Power Supplies are used. Then, the load is distributed between two power supplies, which reduces the risk of fire and gives video cards room for action.
Regular synchronized
CHIEFTEC A-135 (APS-750CB)
Rice. 3. CHIEFTEC A-135 (APS-750CB)
In first place is one of the most cost-effective, if not the most cost-effective model to date.
Its efficiency is 85%, which is very high today. Power – 750 W, there are connectors for 4 video cards.
This equipment is cooled by a 140 mm fan.
It works almost silently, which is also very important.
The model has built-in temperature and load sensors.
Therefore, the equipment is protected from overheating and overload. According to the manufacturer, 10,000 hours of operation are guaranteed.
Pros:
- high technical characteristics;
- light weight;
- excellent efficiency.
Minuses:
- noisy at very high loads;
- If you constantly use it to the limit, it will quickly fail.
CHIEFTEC A-135 (APS-1000CB)
Rice. 4. CHIEFTEC A-135 (APS-1000CB)
This is a more powerful sample - 1000 watts. But its efficiency is the same - 85%.
This model has almost the same advantages as the previous one - an excellent cooling system and minimal noise even at the highest load.
There is also protection against unforeseen situations, for example, voltage surges.
This sample will be able to support 4 video cards, but their total power may already be higher than that of the APS-750CB.
As you can see, the advantages and disadvantages of both CHIEFTEC representatives are the same.
They have excellent efficiency, but low overall power. For a novice miner, any of these options is perfect.
Pros:
- can work for wear;
- low price;
- quality cables.
Minuses:
- you come across a bad assembly;
- burns out over time.
Seasonic Prime Gold (SSR-1200GD)
Rice. 5. Seasonic Prime Gold (SSR-1200GD)
This is one of the most powerful models that are suitable for mining.
It will be able to provide 1200 watts. Seasonic Prime Gold has 8 slots for video cards.
But experts recommend connecting less. You will be able to freely use 6 cards.
Today this is very good. There is very little noise during operation.
Seasonic Prime Gold also has a significant disadvantage. It has 8 connectors, and 4 PCI-E cables. Therefore, you will have to look for the right wire yourself.
Pros:
- durable (12 year warranty);
- quiet operation;
- high quality components;
- excellent package.
Minuses:
- The cables are a little short (subjective), there are no others.
go
Basic PSU safety: do not connect two video cards to the same cable
Before you start connecting two power supplies in one farm, you should check that everything is connected as needed.
The lack of power has very tangible reasons - a lack of power cables.
For example, this is what PCI-E connectors look like. Modern power supplies come in two types of design - modular and monolithic, with pre-wired connectors. PCI-e connectors are used to connect video cards. There can be up to six of them on one power supply.
Appearance of PCI-e and MOLEX connectors on the power supply.
Power supplies have 7 types of connectors, or connecting elements. In mining, we are interested in the Molex connector and PCIE with 6 (4+2 or 6+0) and 8 (4+4 or 8+0) pins. Let's highlight them in a schematic diagram.
Each power supply has up to 6 MOLEX connections and up to 6 PCI-E connectors. Molexes are high-load connections that combine 12V and 5V lines. They can be used to connect video cards, for example via a Molex-PCIE adapter.
For example, this is what a MOLEX-PCIe adapter looks like, they take up two Molexes at a time. They are used when they want to power a video card, but there are not enough free connectors. But this is not always reasonable.
Using Molex connectors to connect a video card is risky.
Molex is not designed for a video card; it is unlikely to be able to output more than 35 W. So, two Molexes will provide a “safe” 70 W via the PCI-E connector, and if the video card needs 250 W, then there will be problems.
Let's imagine the situation: we have a 1080 Ti at 250 W. Monstrous card. We connected it through an 8-pin connector using real PCI-E at 12V and through an 8-pin connector via Molex, which sits at a conventional 12V. Molex conductivity limit is 11 Amps per pin, or 44 Amps per connection. The average video card needs from 100 Amps.
We get: the card takes power from one PCI-E connector and additionally loads the lines of the Molex connectors. As a result, double load on the 12V line. Through a single PCI-E, the card receives exactly as much as it needs.
Do not connect more than two cards to one 12V line.
The power supply has cables for each type of connector.
One power supply, under ideal conditions, can connect as many as 12 video cards. True, only physically - although there are enough connections for a whole dozen video cards, technically the power supply will not be able to pull them out. Previously, we wrote [how to determine how many power lines a power supply has].
On the power supply board, for one cable there is one set of transistors, not two. They have their own estimated power, after which they will go into defense. Let's turn to common sense - they hung two 250 W video cards on one cable and ordered them to work “to the limit”. The unit has a limit on the 12V power line at 500 W. Next comes the smell of melted wiring, a burnt-out unit, and the equipment being sent to Valhalla.
To avoid overloading the power supply, you should follow a simple rule: one cable - one video card. There is only one video card per cable with two PCI-e connectors. If there are two connectors on the cable, then you should not connect two video cards to them - the power supply is not designed for such a scenario. The same rule is true for Molex connections.
Video cards via the Molex port should be connected carefully.
The limit of such ports is 35 W per connection. It should be connected via a “safe” adapter, with two Molex connectors to one PCI-e. But the connection via an adapter should not be the main one, so that the power supply does not get fried with a crust.
How to calculate the power of a power supply for a farm?
The recommended number of video cards for one power supply is 5. This is the limit. So, for 5 video cards of the 1080 Ti level you will need a power supply of one and a half thousand watts - you need to take it with a margin of 20% of the calculated power.
To select the power for the power supply, you must specify the exact power requirements of each component.
- Cooling. 5 watts per cooler-turntable and 30 for the air cooler.
- Video card. Consumption is equal to the stated TDP.
- CPU. Consumption is equal to the stated TDP.
- Motherboard. Standard, within 15 W.
You can calculate the power of the power supply [on the Coolermaster website] or manually using an Excel spreadsheet. For example, here is [a calculator that will give advice on how many PSUs you will need for your build]. Copy it and use it to your advantage.
Synchronization of power supplies as a type of risk management during mining
Using two power supplies is simply cheaper than using one, but powerful one.
In 2022, farms with 6 video cards are more often built using two power supplies synchronized via an adapter. Using two power supplies allows you to get 2 or 3 kW of power at a cost significantly lower than what is required for a single unit of several kW.
For example, two ChiefTec 750W units will allow you to power 8 video cards with a total power of 1500 Watts. In total, this is 1500 watts for 170 dollars with a power supply from a famous company. Whereas one Seasonic SSR at 1300 Watts will cost as much as $500 per unit.
When synchronizing the power supply, risks associated with power supply are reduced by 50%.
One power supply has burned out - the second will continue to work. The farm will not be at peak production, but will be alive and will continue to produce.
Server
DELL DPS-1200MB A
Rice. 6. DELL DPS-1200MB A
The power of this model is 1400 W.
It will be able to work with 5 or 6 video cards.
As you understand, the power of video cards can be greater than that of the models we reviewed above.
The efficiency in this case is a record 94%.
Pros:
- protection against overheating and voltage surges;
- 24/7 work.
Minuses:
- high price;
- difficulty finding a product.
IBM DPS-2500BB
Rice. 7. IBM DPS-2500BB
The creation of the famous computer company IBM surprised many geeks and just people interested in the world of technical innovations.
The model can provide very powerful video cards.
This is possible due to the fact that the power is 2320 W.
At the same time, its price is not much higher than that of conventional (non-server) models.
It also has an excellent cooling system that doesn't make too much noise.
There is no downside to the high price. But there is a disadvantage associated with a shorter service life than other models. Such power supplies fail more often.
Pros:
- can draw 12 cards;
- low price;
- low noise level.
Minuses:
- not very long service life;
- difficulty finding a product.
