Bitcoin Forum

Keywords : BAMT, Radeon R9 290x, gpumon, dummyplug, HDMI, DVI-D, virtual currency, litecoin

1) Issue description :
The rig was working fine with one GPU with BAMT installed. Adding a second Radeon R9 290x GPU, the BAMT main screen displayed :
------ snap --------
GPUs Detected:
0 01:00.1 AMD Radeon R9 290 Series
1 02:00.1 AMD Radeon R9 290 Series
------ snap --------
which sounds perfect. Both GPUs are detected at hardware level.

However on the shell terminal running gpumon, the second GPU would not show up. No status monitoring, nor hash rate. The cumulated hash rate of the rig does not account for the second GPU.
Nevertheless, both boards are actually mining. Sure about this because the hash rate estimated by the mining pool I subscribed to, is twice what it was before (internet dashboard access).
If I pug a TV set on the HDMI output, it does not solve the issue.

2) Apply corrective patch to common.pl file
The patch is described in :
https://bitcointalk.org/index.php?topic=370072.msg4179463#msg4179463 (https://bitcointalk.org/index.php?topic=370072.msg4179463#msg4179463)
Appears to be fine. The second GPU shows up in gpumon, with proper status line, individual and cumulated hash rates.
However not satisfactory : when I unplug the TV set to return it back to its place (upon family pressure), the issue on gpumon display is still present.

NOTE : even when the TV set is not power supplied, the simple cabling of the HDMI line is enough to solve the issue. This sounds like a need to lure the digital source (the GPU) about the presence of a sink.

3) Implement a dummy plug for the HDMI output
I buy a HDMI male/DVI-D female adapter (2.78 euros at Amazon).
http://ecx.images-amazon.com/images/I/31J3EKB0F0L._AA160_.jpg
http://www.amazon.fr/HQ-HQSSVC003-Adaptateur-HDMI-DVI/dp/B000LMQ30I/ref=sr_1_1?s=electronics&ie=UTF8&qid=1393764356&sr=1-1&keywords=hq+hqssvc003+adaptateur+hdmi-dvi (http://www.amazon.fr/HQ-HQSSVC003-Adaptateur-HDMI-DVI/dp/B000LMQ30I/ref=sr_1_1?s=electronics&ie=UTF8&qid=1393764356&sr=1-1&keywords=hq+hqssvc003+adaptateur+hdmi-dvi)
This is because I do not want to jeopardize the brand new HDMI connector of the GPU itself. Thus better use a low cost adapter for experiments.

NOTE : this is NOT a dummy plug on the VGA analog signals existing on the DVI-I plugs. As the R9 290x does not have analog outputs, the DVI connector is a DVI-D (outputs digital signals only).

On the DVI-D side (female) I connect pin 14 (+5V) to pin 16 (Hot Plug Detect), through a 3.3kOhm resistor. One can see at this address the pinout for an HDMI to DVI-D adapter :
http://pinouts.ru/VideoCables/hdmi_dvi_cable_pinout.shtml (http://pinouts.ru/VideoCables/hdmi_dvi_cable_pinout.shtml)
This figure should set a 5*15/(3.3+15)=4,1V voltage on the hot plug detect input (assuming a generic 15kOhm input impedance). Not checked yet...

Then I plug the adapter and I restart the rig. And YES, both GPUs show up on the cgumon display.

Click on the icon below to see the photo of the dummy plug. By the way, the 3.33kOhm resistor consist in three parallel mount 10kOhm resistors (I had not 3.3 ones).
http://nsm08.casimages.com/img/2014/03/02//mini_14030206264817299712028784.jpg (http://www.casimages.com/img.php?i=14030206264817299712028784.jpg)


Hope this post can help someone.
Happy mining to all !