<p>The -gpu=X command line is telling it which of your CUDA devices it should use, not <em>how many</em> it should use. Like most things written by programmers, the index starts at zero.  If you have two video cards, run it once at the command line with -gpu=0 and then a second time again with -gpu=1.  Once you work out your ideal fine tuning on aggression, gpugrid and gputhreads (if you do at all), it's easiest if you make a batch file (unless you're using GUIMiner, in which case create a new CUDA miner for the second card, same extra flags on both other than gpu=0 or 1).</p>

<p>You can execute it twice without specifying the GPU and it will certainly run, but from the console output it appears it assigns both of them to the first device.</p>

CC BY-SA 3.0
2013-11-27T07:19:57.603Z
2013-11-27T07:19:57.603Z
user9433
<p>The simple solution is to copy and rename the command so you run 2 separate instances of the same command.  The other option is seeing if adding <code> -threads=2</code> ACTUALLY does let you use both cards.  I have had issues where the threads were CPU threads and not cards and times it ' just worked ' on the same system.  running the command twice had it run 2 instances one per card and seemingly random which card was first every once in a while.</p>

<p>I have a XP box for CUDA mining on dual ( not connected ) 8600 GT cards and used GUIMiner Script to find out what batch files were created for each ( as new CUDA miners for litecoin ).  With some tweaking, they can do BTC or LTC mining.  What little time I have used rpcminer ( and hair pulling ) it seemed to ' kinda work ' when I ran it twice to get both cards mining as separate cards.</p>

<p>As to the profitability of GPU mining... I still have a ' day job ' and am looking at investing in ASIC miners for BTC.</p>

CC BY-SA 3.0
2013-07-25T02:38:03.673Z
2013-09-26T12:54:22.813Z
2013-09-26T12:54:22.813Z
nybbler905
<p>I'm using rpcminer-cuda to have a play around mining some bitcoins.  I have 2 NVidia cards, and I understand this is not ideal for any profitable mining.  I would however like to have them both working at the same time.  Presently the output from rpcminer-cuda when it starts up is:</p>

<pre><code>rpcminer-cuda.exe -url=myurl -user=myuser -password=password

Client will start 1 miner threads
2 CUDA GPU devices found
Setting CUDA device to first device found
</code></pre>

<p>How do I make it use both cards at the same time?  Do I need to tell it to start two threads or is there some other commandline switch I need to use?  I've tried adding -gpu=2 but it seems to be ignored.</p>

<miner-configuration><gpu-mining>
How to use both CUDA GPUs?
Matt Parkins
# How to use both CUDA GPUs?

(Asked by: username_0 on 2013-07-10)

I'm using rpcminer-cuda to have a play around mining some bitcoins.  I have 2 NVidia cards, and I understand this is not ideal for any profitable mining.  I would however like to have them both working at the same time.  Presently the output from rpcminer-cuda when it starts up is:
rpcminer-cuda.exe -url=myurl -user=myuser -password=password

Client will start 1 miner threads
2 CUDA GPU devices found
Setting CUDA device to first device found

How do I make it use both cards at the same time?  Do I need to tell it to start two threads or is there some other commandline switch I need to use?  I've tried adding -gpu=2 but it seems to be ignored.

**Tags:** miner-configuration, gpu-mining


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## 2 answers

### Answer by username_1 on 2013-11-27. Score: 2 | Accepted answer

The -gpu=X command line is telling it which of your CUDA devices it should use, not *how many* it should use. Like most things written by programmers, the index starts at zero. If you have two video cards, run it once at the command line with -gpu=0 and then a second time again with -gpu=1. Once you work out your ideal fine tuning on aggression, gpugrid and gputhreads (if you do at all), it's easiest if you make a batch file (unless you're using GUIMiner, in which case create a new CUDA miner for the second card, same extra flags on both other than gpu=0 or 1).

You can execute it twice without specifying the GPU and it will certainly run, but from the console output it appears it assigns both of them to the first device.


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### Answer by username_2 on 2013-07-25. Score: 0

The simple solution is to copy and rename the command so you run 2 separate instances of the same command. The other option is seeing if adding  `-threads=2` ACTUALLY does let you use both cards. I have had issues where the threads were CPU threads and not cards and times it ' just worked ' on the same system. running the command twice had it run 2 instances one per card and seemingly random which card was first every once in a while.

I have a XP box for CUDA mining on dual ( not connected ) 8600 GT cards and used GUIMiner Script to find out what batch files were created for each ( as new CUDA miners for litecoin ). With some tweaking, they can do BTC or LTC mining. What little time I have used rpcminer ( and hair pulling ) it seemed to ' kinda work ' when I ran it twice to get both cards mining as separate cards.

As to the profitability of GPU mining... I still have a ' day job ' and am looking at investing in ASIC miners for BTC.


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