On Geth Version: 1.6.2-unstable miner.start() returns null, it used to return number of processes assigned. Is it normal? miner.start(num) num identifies the thread number?

> miner.stop()
> miner.start(4)

I have a small private net and there is only one miner. The miner used to work for almost couple of months with 503.7 KH/s (since it has been launched with geth v5.9) but now it works with 103.7 KH/s when I updated geth with 6.2 there is this sudden drop down. This drop down affected all the miner's hash rate and I observe that all's hash-rate is drop down around 5 times.

This change occur for my other nodes where hash-rate is get dramatically slower. When I check top geth consumes all the CPU power, I assume miner works with full CPU power.

[Q] What might be the reason for miner's hash rate drop down (almost 5 times slower)? Could it be related to geth's update on version 6.2? Did anyone faced with similar issue?

[Q] This is very inefficient. If the node use much smaller hash-rate why on the background does the CPU consumes all the power? or just hash-rate calculation updated.

Thank you for your valuable time and help.

  • 1
    Returns null basically means that it does not return anything. The javascript console always displays the return value, even if there is none.
    – q9f
    Commented May 19, 2017 at 10:09
  • miner.start(n) used to return number of processes assigned on the background. @5chdn
    – alper
    Commented May 19, 2017 at 11:45
  • Both issues might be worth creating a ticket on github.
    – q9f
    Commented May 19, 2017 at 12:56
  • Roger that: github.com/ethereum/go-ethereum/issues/14487 @5chdn
    – alper
    Commented May 19, 2017 at 13:53

1 Answer 1


This issue has been solved.


Missing hashrate was a regression. It was fixed in the latest stable release. Please update. As for the potential slowdown, we did switch out the C++ ethash code to a Go version a couple years back. CPU mining in general is not feasible, so there's not much point in striving to absolute max out performance. A well-enough performing CPU miner is enough for private/testnets.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.