This is a common problem whose cause is not well known. You can try switching miners, switching flags, or switching OpenCL versions. Usually you can find a combination that resolves the problem. I've seen this question asked several times and I've not yet seen a solid answer.
I suggest to use one of the updated cpuminer versions which support more than one algorithm. This way you are also set up to mine different coins which use other PoW functions. The most versatile one is tpruvot's fork:cpuminer-multi. For me this one worked out of the box on a recent Ubuntu 14.04 installation.
The syntax is similar to all other cpuminer ...
Presumably, you have no backup pool configured. So if your server doesn't respond quickly enough, poclbm just fails over back to the primary pool. If these are only happening occasionally, I wouldn't worry about it. Anything that momentarily prevents the RPC call from getting a response can do this.
lspci lists PCI devices. ./poclbm.py lists OpenCL devices. If the former finds the device but the latter does not, your second GPU must not be registering as an OpenCL device.
Ubuntu 11.10 has a notorious reputation for multiple-GPU bugs. (See here and here.) I personally have had issues with 11.10 mining that were resolved simply by switching to another ...
AMD Catalyst drivers have a bug which result in 100% CPU usage.
The current drivers (11.9 as of writing) solve this bug for SINGLE GPU systems but MULTIPLE GPU systems are still affected by the "100% CPU bug". This isn't anything that can be fixed in software it must be fixed by AMD driver team.
The 11.10 preview driver also doesn't (at time of writing) ...
After looking at the (quite old) source code of poclbm, there is a commented line that creates the SSL connection. Not sure it is the reason but I guess it doesn't support HTTPS in its last version.
I changed to DiabloMiner (I had to add my self-signed certificate using the InstallCert.java tool)
I can now mine over HTTPS. Next step is a pool...
After spinning-up my Raspberry Pi and registering an account at slushpool I've had success with the following process:
sudo apt-get install automake autoconf pkg-config libcurl4-openssl-dev libjansson-dev libssl-dev libgmp-dev make g++ git
git clone https://github.com/tpruvot/cpuminer-multi
Check out the commands: ./...
This indicates that your miner couldn't get work from the pool fast enough and so some mining power was wasted. If this only happens occasionally, I wouldn't worry about it. If it happens often enough that it's impacting your mining rate, you may wish to configure a backup pool. If it's happening because your Internet connection is slow or unreliable, there'...
From the poclbm source code, Switch.py line 219:
say_quiet('%s[%.03f MH/s (~%d MH/s)] [Rej: %d/%d (%.02f%%)]', (if_else(verbose, miner.id()+' ', '') , rate, round(estimated_rate), rejected_shares, total_shares, float(rejected_shares) * 100 / total_shares_estimator))
And how estimated_rate that found, you ask?
I tried looking at the ...
You could check the temperature on the devices, the one active should be running much hotter than the others.
If they're all running hot the bottleneck is elsewhere (CPU or memory/bandwidth). If none of them are running hot you've bought one hell of a CPU to get 200Mhash.
Else it's advisable to check whether or not you can use the non-default videocard at ...