Hi, does anybody have experience with overclocking Bitmain L3 or L3+ miner? What is the safe frequency to go? Thanks.
I’ve overclocked a number of different types of miners, there are a few areas you really need to watch when doing so:
Chip temps. The obvious one, as you overclock you will see temps go up geometrically as opposed to linearly as you reach the saturation point on the heat sinks. Likewise efficiency will drop like a rock. Don’t trust the on board temp sensors, use an IR gun to watch for the hotspots forming on the backs of the boards as well.
DC-DC temps: These are just as critical as chip temps. As the high-side FETs overheat they will cause an avalanche effect where the +12 supply will start to cut through to the chips, increasing the current draw. When this happens the FETs will either dead short or the supply will shut down (if it’s a good one. Most are not). Dead short will set fire to the FETs, damage the board, and possibly wreck the hashing chips. Happens very quickly
PCIe plug: Monitor the temps using an IR gun on the PCIe plugs. As you pull over 250 watts per plug the connectors start to heat up, which increases their resistance which causes more voltage drop which increases the current draw which leads to more heat which… You get the picture. Also if you use cheap power supplies with 18 gauge wire the wire will heat up and the voltage at the miner will drop from 12v down to 10v or less. This will not stop the miner, what it will do is cause the miner to draw more current which causes resistance effects to become more pronounced which causes more heat which… well, that.
I don’t have an L3 or L3+ here in the shop, but if someone would like to send me one for review for a week or two I can give you a lot more information and whatever litecoin it mines during that time. Could be helpful, drop me a line.
Thank You for such a detailed answer! I appreciate your profesional view! On the other hand, I think you bit overcomplicate things, from my experience OC is not that dramatic if you do it just a little. Thats my aim. Thats why Im looking for someone with L3 experience. But again, thanks for interesting technical post.
Not a problem. I’ve just been overclocking a number of types of miners for awhile, and have seen some complicated results (ie: fires) from people who don’t quite think about everything. Making sure the resulting miner is on a metal surface (not a rug in case the capacitors shot and flames shoot out of it and using a power supply that is not too big is a good way to go normally.
As for clocking the chips themselves, look around on the board for the oscillator and the timmer resistors. Changing those out can yield some interesting changes if they won’t let you fiddle with the firmware.
I need to get an L3 in for testing one of these days.
Have you got any L3+ for testing ? I was thinking about overclocking mine but I want to do this as informed as possible. I’d really use an advice.
No, haven’t gotten one at this point. Can you try bumping up the frequency a bit at a time and watch the temps?
I have found that overclocking the L3+ is definitely worth it. Stock frequency 384M @ 504 mh/s 850w with the apw3++. Overclocked 462M achieves 610+ mh/s. I have overclocked all 3 of my L3+ since the day I purchased them (several months ago). The overclocking leads to more power drawn from the wall. I would recommend only overclocking the units while on 220/240v and making sure you have a strong enough power supply to do it. Even with overclocking the units, I still have never had any issues with the miners.
I made a steemit post and youtube video on this subject comparing the stock frequency to the overclocked frequency and the results were very promising. Please see the links below.
Hi, have you tried to overclock it to 650/Mh ?
I can get a stable 620mh with setting 475m on l3+ however they seem to pump out a few HW errors. You can try that setting but i suggest trying 462m first for 600mh. Make sure the power supply will do 1000w easy.
I know it’s off topic but does anyone here have an experience over clocking the A4 Dominators?