Windows disables video cards with no monitors attached (at least valid for ATI/AMD ones). One solution is to plug the monitor into each card before starting a miner on its OpenCL device. Once the miner is up and running you can disconnect the monitor but you would need to plug it in again if you need to restart the miner.
For the technically inclined there exists a very simple solution: just three 68 Ohm resistors bridging the VGA signal pins to GND. Here you can read in details how to create a dummy VGA plug yourself: http://www.overclock.net/folding-home-guides-tutorials/384733-30-second-dummy-plug.html
Topic: HD 6850 + HD 4850, second card can't use OpenCL? (Read 5562 times)
Yesterday I had same problem with 6950 & 5870. After connecting the cable to the second device (before booting),on the second device was appeared OpenCL.
I think it has something to do with the fact that you have two cards in one machine. I couldn't get Windows to work with two 5850 and had to (with pleasure) switch to Ubuntu. Works like a charm (thanks to Raulo).
EDIT: Sorry, you didn't say that you're on Windows, but I am assuming so since you use ATI Stream SDK 2.3?
EDIT: Sorry, you didn't say that you're on Windows, but I am assuming so since you use ATI Stream SDK 2.3?
My HD4870 is OpenCL capable and afaik the 4850 is using the same chip, so basically, it should support OpenCL as well.
Sorry, I should have mentioned that I'm using Windows 7 64bit.
Read my tutorial, especially the aticonfig --initial part.
https://bitcointalksearch.org/topic/m.47174
You have probably not updated xorg.conf. Do you have two Section "Device" in /etc/X11/xorg.conf one for each of your cards? If you do update, rename your former xorg.conf first.
https://bitcointalksearch.org/topic/m.47174
You have probably not updated xorg.conf. Do you have two Section "Device" in /etc/X11/xorg.conf one for each of your cards? If you do update, rename your former xorg.conf first.
So I'm using m0mchil's bitcoin miner and I've had it working fine on the HD6850 @ 220mhash/s, and I've since added a second card in - a HD4850 I had laying around.
I'm having problems getting this one detected as an OpenCL capable device, I've removed and reinstalled ATI Stream SDK 2.3 as well as reinstalled video drivers + opencl driver, didn't make any difference.
GPU Caps Viewer doesn't list it as an OpenCL capable device either. Anyone know what could be preventing this from working right? It seems the 4xxx series doesn't support OpenCL properly but there are others in the thread claiming to be using 4800 series cards.
I'm having problems getting this one detected as an OpenCL capable device, I've removed and reinstalled ATI Stream SDK 2.3 as well as reinstalled video drivers + opencl driver, didn't make any difference.
GPU Caps Viewer doesn't list it as an OpenCL capable device either. Anyone know what could be preventing this from working right? It seems the 4xxx series doesn't support OpenCL properly but there are others in the thread claiming to be using 4800 series cards.
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