I have a machine that's running Windows 10, with 2 AMD R9 290s, and I'm trying to use geth with 2 instances of ethminer, one for each card. I've also set up port forwarding for port 30303, and geth is allowed through Windows Firewall.
The binaries for geth and ethminer were downloaded from build.ethdev.com.
Whenever I try running ethminer, the first instance always runs normally, but then the second immediately gives me this error: "DAG generation failure. Reason: Permission denied". So I've never been able to get both cards mining at the same time.
I've tried
- reversing the order in which I start up each card
- using geth with --rpc, and alternatively, with --rpccorsdomain
- starting up the ethminers before geth
- running cmd as admininstrator (I imagine sudo might have worked if I had been using linux

Is there anything I can do to fix this? I'd appreciate any feedback.
Comments
I did do a google search after I read your post, and what I found (disabling DX by tweaking some settings in AMD CCC) didn't work.
If you launch a second instance of "ethminer" using "ethminer -G --opencl-device 1" you receive the error message: "DAG generation failure. Reason: Permission denied" even if launching it with full Administrator rights.
Is there a fix?
But first, I would check the order in which your GPUs are detected by ethminer, by typing "ethminer --list-devices". If you have onboard graphics, hopefully it would appear last on the list, after the discrete graphics cards. That's because when you include the argument "-t 2" in the command, that tells the program to use the first 2 GPUs that it detects.
For me, initially the Intel graphics processor was listed first, and the GPUs, although appearing on the list as well, weren't recognized by ethminer at all. After trying a few things, I was only able to fix this by reinstalling, which thankfully worked.
-- opencl-device 1 --opencl-platform 1
this was hte only way I could get my laptop to mine using the Nvidia GPU. Otherwise it would always attempt to use the inbuilt intel.
Might help someone.
Sorry if this post is a duplicate. It doesn't look like the last one posted.
Sorry if this post is a duplicate. It doesn't look like the last one posted.
I reinstalled the OS, which in my case is Windows. But by now you've probably fixed the problem yourself
If you run into this problem in the future though, there is another possible solution. I haven't had the opportunity to test it, but it worked for someone on reddit (skip to the last paragraph).