Antminer A3 – Underclocking & Overall Setup

I have had an A3 for Sia and now SiaPrime since around the time they were released.

I always lower my fan speeds to ~%50 for acoustics, this likely could void your warranty but I would argue there are other far more damaging thing you can do, like shoving live pci-e wires in upside-down or covering up the intake/exhaust. At a certain heat level ~100 degrees Celsius, the fans will flip to 100% speed until cooled, but you likely will have crashed one of your 3 x A3 hashboards, at this point you will need to raise your fan speed or start underclocking.

The observations about underclocking not being linear are true from experience, I think of it as resonance frequencies rather than straight intensity. As you step your clock speed down by 6 MHz increments you notice the power usage may go down but so has your hashrate, but the temp is running a bit hotter and you scratch your head, step down again and you may have complete instability at that frequency, with another step down the temp/power/hashrate might be lowered and this could be considered a “stable” increment. I have underclocked as low as 350 at 20% fan speed with a cold air intake and it was stable.

Hot air rises so I bring the miners lower to the ground, I used to have them on the bare ground but now use a heat dissipating mat which keeps the ground from being heat insulation, there are 3D files for 5 to 6″ fan shrouds you can print and attach to your exhaust and pull with an inline fan to another area or outside. I have always thought miners could/should colocate with businesses to help heat their spaces (seasons and shutting off miners due to profitability make it complicated), humidity can be adjusted, seems waste that clean heat especially if you are on a green electrical grid, if you have a space heater that makes money why not use it?

Voltage is very important, even your ~110V power can be as low as 100V or over 120V in some areas and at certain times of the day. Higher voltages do provide more efficiency and using 220V certainly opens you up to a new category of power supply, though 220v is unforgiving if you are electrocuted. You will still have voltage drop over your 12V DC cables, which there are calculators for, they cause and are effected by magnetic interference, run your cables too long or with thin wire and that 12.3V pin is actually at 11.8V, I would suggest well made 12-14 AWG custom length PCI-E 6-pin cables with all 6 wires not 2 x [3 bridged to 1 long wire] for -ve +ve. Every power supply has a different efficiency rating and a different “sweet spot” when it comes to load  this link explains how you may use over 10% extra power using a “Bronze” rated power supply over a “Platinum” rated one. An important note is that most quality power supply units have a lifetime warranty, so combine that with the power savings and it is worth the money. The heat from the power supply will have to dissipate, quite a bit of heat is produced at a higher load, since much of the wasted power is the heat released, a lower efficiency PSU could also produce more heat.

If you rarely handle networking you will need to be able to figure out the assigned IP address for the miner to login and input some urls with specific port numbers for mining, at the end of your mining address you can often append something like .miner1 to your user address (often a payment address) this will show the miner as a specific worker which helps if you have multiple miners, you could also use iptables to set your TOS Bit to 3: for “No Delay”, an important part of forming block shares is submitting them before the block solution is found so you do not want your data being sent down a high latency but reliable route or a high latency but high throughput route, we want minimal delay. You don’t need to port forward from the WAN, the miner will open up it’s own connections, but you do need to make sure that the miner traffic is not delayed through your network, for example I would be connecting as close to your gateway as possible, especially not through a router that handles all the wifi in your place, most modern routers will use WMM and as an example smoothly route a video from reddit to your cellphone causing delay to other packets, I would not disable WMM, just don’t add your miner to or behind a collision domain.

I will try and add some more ideas if I can.

Stefan Crawford

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