In order to set up the ethminer I need the MHash value. I'm testing CPU, so I ran:

ethminer -M

and I got a weird output:

Trial 1... 0
Trial 2... 0
Trial 3... 0
Trial 4... DAG  17:33:59.896|miner0  Generating DAG file. Progress: 0 %
Trial 5... 0
 ⚡   17:34:04.302|ethminer  Terminate worker 500 ms
min/mean/max: 0/0/0 H/s
inner mean: 0 H/s
Phoning home to find world ranking...

I have the DAG file generated and everything should be set up (I tried to mine setting a number and it did report hashes per second and stuff). So I'm not sure if the -M switch is not working properly or I'm doing something wrong, and I need the mhash value so I don't mess it up and end up losing money.

Thank you.

  • Can reproduce this, probably a bug. I also get 0 H/s using -M.
    – q9f
    Commented Aug 6, 2016 at 21:16
  • I read on another forum (irrelevant to mining) that some GPUs take time to warm up. Try running your benchmark with --benchmark-warmup 10. Good luck!
    – user9149
    Commented May 29, 2017 at 5:30

3 Answers 3


You can use chfast's Fakeminer to do cpu benchmarks, see https://github.com/chfast/ethash/tree/master/test/fakeminer


-M,--benchmark Benchmark for mining and exit; use with --cpu and --opencl.

Try with ethminer -M --cpu or ethminer -M --opencl depending on CPU / GPU benchmarking.

Edit : For some reason -M -G gives 0 hashrate while -G -M works. The ordering should ideally not matter, but maybe it does.


You could try mining on a private Ethereum blockchain and look at how long it takes you to mine blocks as the difficulty rises. The hashing speed can then be calculated as hash_rate = difficulty / block_time_in_seconds. Alternately, you can mine on a pool or the test net (but I believe etiquette dictates you shouldn't mine on the test net for too long if you have an sizeable mining capacity -- which should be fine given you're testing a CPU). Pool mining is potentially less accurate.

See also How do I decrease the difficulty on a private testnet? if you want to try a private blockchain.

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