Should you buy a used mining GPU or do you want wait till miners move away completely from GPU mining and there are enough new cards at MSRP, ready for purchase? You can always find used Mining GPUs in the market and we may see a flood of new ones soon. With China’s cryptocurrency crackdown, we’ve been hearing about GPUs previously used in mining setups being sold second-hand. Whether you want to buy these second hand GPUs for gaming or even mining, there are things to consider, before and after the purchase. This video is inspired by LTT’s new video about Mining GPUs and we try to dig dipper in this topic. You need to know how miners use these GPUs and what the common problems are, in order to be better prepared. You can watch that video first, if you haven’t already.
Knowing how miners use these GPUs and the common problems can help you make better decisions and be prepared.
Typical Mining Environment
If you think all miners have tidy, datacenter like environment with HVACs, totally dust free and temperature controlled, you are wrong, big time! You can just do a quick search in Reddit or YouTube to see the mining rigs most people use and the farms in abandoned factories usually in countries with cheap electricity.
In these environments, the main tool to clean the GPUs are either blowers or an air compressor! And they do it once the cards reach temperatures higher than the norm, usually above 80 degrees. They have some staffs to monitor the rigs and the mining console and when they see high temperatures while the fans are spinning at 100%, they know that something is wrong with the fans, or the air cooling or the card is totally dusty. They usually blow compressed air to the card while it is ON to avoid any downtime.
Dust, Temp and Humidity
Miners don’t do a total cleanup by detaching the fans and the heat sinks and using brushes, because it’s a time consuming job when you have a thousands of them around, and the warranty stickers on the bolts shouldn’t be scratched, because they know that at some point they want to resell the cards and buy new ones with better hash rates. Dust and humidity results in layers of dirt forming on top the heatsink blades and other power components like the VRMs.
When you buy a used card, you have to detach the fans and the heatsink, brush them and use cotton swabs to remove the dusts and the dirt. A silicon re-paste is also very helpful. You need to have the tools ready and buy a high quality silicon paste for this maintenance job. You cannot simply judge a GPU by its cover. It’s better to dig dipper and take it apart.
Be careful when you detach the heatsink because there are silicon pads on top of the VRMs and you may damage them accidentally. You can also buy some spare pads, they may come in handy. Mining and even gaming for a while can dry out thermal pads and the paste over time and we know thermal throttling can affect the performance.
As I said, miners usually don’t control the humidity and some even use coolers that make the air more humid. At best, they control the ambient temperature.
GPU fans aren’t designed to spin at high RPMs for a long period of time and this is the typical situation in mining rigs. GPU fans can wear out, and most significantly, the fan’s bearings will eventually wear out after prolonged usage. You have to see if the fan blades move smoothly with a sharp push or if they feel stiff, if it’s stiff then the bearings are probably gone. If the blades are very loose and they can be tilted, the problem is either a worn out bearing or a shaft with reduced diameter because of shrinking. A faulty fan is also noisier when it’s ON and can’t cool down the GPU effectively, even when the heatsink is totally clean and the silicon paste is new.
It’s better to check the availability and the cost of new fans before buying a second hand mining GPU, because sometimes you have to replace them, rather than fixing them with some lubricants temporarily, especially the ones that are on top of the main compute unit. These fans are sourced from china and some are quite costly because of the high demand. Ordering them directly from Chinese websites like AliExpress can be a time consuming task with the current supply chain and shipping problems.
Some fans are easy to replace and you can swap them individually, but there are a lot of GPUs with fans attached to one connector. Changing them individually requires cutting the wires and soldering a new one.
PCB, Back plate
Because of the temperature difference between mining during the day and night, especially in the summer, and the fact that mining GPUs work 24/7 at full load, there is a high stress on the graphic card’s PCB and the ones without an adequate back plate are usually bent. A visual inspection before buying a used GPU and checking the pictures of the model is important. A bent PCB can cause serious problems to the memory sticks or the GPU itself, even if it is working correctly right now. Try to avoid a bent PCB even if the card has a back plate.
Some second hand GPUs are safer to buy because of the back plate and the fact that they use silicon pads to cool the PCB using the backplate.
You have to know a few details about how miners change the configuration of the cards. They usually try to under-volt and under-clock the GPU, while increasing the frequency of the memory. This is how they get a better hash rate. Most Hashing algorithms embrace a fast and overclocked memory.
Because of this, the memory chips get very hot. They are not usually connected to the heatsink and this makes the PCB hot. That’s why graphic cards with back plates and pads on the memories are always better, especially if you buy them second hand.
Besides increasing the frequency of the memory, miner try to change the timing of the memory too. They use bios editors to change the parameters of the card. Hopefully, nowadays most GPUs have dual bios. Most of the sellers also revert the original bios before selling the GPU, but you may receive one with a modified bios. Drivers usually detect a modified bios and don’t let you continue the installation because the checksums are different. You can download the original bios ROM file and flash it to the bios. There are other YouTube videos that teach you how to do that if this is needed. Beside the software flashing method, a faulty bios can be fixed with a hardware programmer. Using a CH341A module, you can flash the bios file to a bricked rom chip.
Power and Line Regulation
Another common problem with the mining GPUs is the voltage fluctuation and noise on the power line. In mining farms, hundreds or thousands of switching power supplies are connected to the mains. They create a shitload of switching noise, the mains voltage drops and the stability is low, because most farms employ a DIY and unprofessional cabling and power management.
The power supplies are not always the top tier models with active PFC and line regulation. Most of the power supplies are also not designed for mining and the ones that are designed for mining in China are not very well engineered or do not use quality components. All these result in more stress on GPU VRMs. Voltage drops on the 12V rail can lead to higher current draw and the fluctuations can lead to magnetic flux changes in the inductor core. The life span of these components will become shorter for sure.
Power supplies also get dirty and dusty, their fans get defective and their life spans drops significantly with mining. Their performance can be affected and as a result, the 12v voltage will not be fully regulated under transient loads.
During the miner software startup, GPUs and CPU take a lot of power for a few minutes to generate the required files and temp data. The fans ramp up suddenly. If you have a lot of miners starting up simultaneously, you can blow a fuse! A lot of miners incorporate random delays in their configs to start or restart the miners after a fault situation or connection problems. But the power spikes can still lead to voltage drops.
If you take a GPU board apart, there is not any visual indication of damaged component, but the problem can be there and it can be detected only using professional equipment.
One of the best tests to evaluate a second hand GPU is the mining itself! If you can mine a Crypto using the GPU for a few hours without a drastic hash rate drop, high temperature or the mining software freeze up, the GPU should be good enough for gaming and other tasks.
If you see error messages in the mining software, high temperatures and hear fan roars, you have a GPU in hand that wasn’t well maintained.
You can compare the hashrate of a GPU with stock bios and default settings with the numbers that you can find on the internet. These hash rates are easy to find. If it is off the stated hash rates by a tiny margin, it is not a problem. Different memory chips on the graphic cards result in different hash rates for an identical models. There are different memory manufacturers like Hynix, Elpida, Samsung and Micron and GPU manufacturers may use different ones in a same model.
You can also ask the seller to send you some pictures or a video of the hash rate info while mining a Crypto like Ethereum, after a few hours of mining.
Miners report GPUs freezeups more frequently and rapidly after a few years of mining. They use scripts to monitor the GPUs and restart the mining rigs when they freeze up. They can identify the GPUs that hang more often and after and inspection and cleanup, if the problem is still there, they try to sell and replace it.
So, the conclusion
High temperature, temperature swings, high or even very low humidity and voltage fluctuations can lower the life span of electronic components. GPUs are no expectation. You can have a card in hand that is functioning normally right now, but in a few months or years you might have a faulty one that is not acceptable for warranty replacement or repairs.
I don’t say buying a used mining card with a good deal is a bad thing, it all depends on the price, your use case, your preparedness for the inspections and repairs and your luck.
With the current GPU shortages, supply chain and shipping problems and greedy scalpers, a used GPU may be your best shot!
Try to hook a good model that looks OK, do the inspection and cleaning, and count on your luck!
Mining does not damage a card, as long as the conditions are closely monitored and controlled by the miners.
That’s it for now. Tell us your opinion about used GPUs and mining cards in the comment section. Will you buy a used one with the right price or do you rather wait and buy one out of the shelf?
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