Running under linux kernel 3.11.6 catalyst 13.4 There are 3 "Radeon 6900" gpus. I have use_all_gpus enabled in my cc_config.xml boinc reports Config: use all coprocessors
but only detects and uses one card.

CAL: ATI GPU 0: AMD Radeon HD 6900 series (Cayman) (CAL version 1.4.1741, 2048MB, 1812MB available, 50 GFLOPS peak)
OpenCL: AMD/ATI GPU 0: AMD Radeon HD 6900 series (Cayman) (driver version 1124.2, device version OpenCL 1.2 AMD-APP (1124.2), 2048MB, 1812MB available, 50 GFLOPS peak)
Config: use all coprocessors

clinfo

Number of platforms:				 1
  Platform Profile:				 FULL_PROFILE
  Platform Version:				 OpenCL 1.2 AMD-APP (1124.2)
  Platform Name:				 AMD Accelerated Parallel Processing
  Platform Vendor:				 Advanced Micro Devices, Inc.
  Platform Extensions:				 cl_khr_icd cl_amd_event_callback cl_amd_offline_devices


  Platform Name:				 AMD Accelerated Parallel Processing
Number of devices:				 3
  Device Type:					 CL_DEVICE_TYPE_GPU
  Device ID:					 4098
  Board name:					 AMD Radeon HD 6900 Series  
  Device Topology:				 PCI[ B#3, D#0, F#0 ]
  Max compute units:				 24
  Max work items dimensions:			 3
    Max work items[0]:				 256
    Max work items[1]:				 256
    Max work items[2]:				 256
  Max work group size:				 256
  Preferred vector width char:			 16
  Preferred vector width short:			 8
  Preferred vector width int:			 4
  Preferred vector width long:			 2
  Preferred vector width float:			 4
  Preferred vector width double:		 2
  Native vector width char:			 16
  Native vector width short:			 8
  Native vector width int:			 4
  Native vector width long:			 2
  Native vector width float:			 4
  Native vector width double:			 2
  Max clock frequency:				 880Mhz
  Address bits:					 32
  Max memory allocation:			 268435456
  Image support:				 Yes
  Max number of images read arguments:		 128
  Max number of images write arguments:		 8
  Max image 2D width:				 16384
  Max image 2D height:				 16384
  Max image 3D width:				 2048
  Max image 3D height:				 2048
  Max image 3D depth:				 2048
  Max samplers within kernel:			 16
  Max size of kernel argument:			 1024
  Alignment (bits) of base address:		 2048
  Minimum alignment (bytes) for any datatype:	 128
  Single precision floating point capability
    Denorms:					 No
    Quiet NaNs:					 Yes
    Round to nearest even:			 Yes
    Round to zero:				 Yes
    Round to +ve and infinity:			 Yes
    IEEE754-2008 fused multiply-add:		 Yes
  Cache type:					 None
  Cache line size:				 0
  Cache size:					 0
  Global memory size:				 1073741824
  Constant buffer size:				 65536
  Max number of constant args:			 8
  Local memory type:				 Scratchpad
  Local memory size:				 32768
  Kernel Preferred work group size multiple:	 64
  Error correction support:			 0
  Unified memory for Host and Device:		 0
  Profiling timer resolution:			 1
  Device endianess:				 Little
  Available:					 Yes
  Compiler available:				 Yes
  Execution capabilities:				 
    Execute OpenCL kernels:			 Yes
    Execute native function:			 No
  Queue properties:				 
    Out-of-Order:				 No
    Profiling :					 Yes
  Platform ID:					 0x00007f10e6101520
  Name:						 Cayman
  Vendor:					 Advanced Micro Devices, Inc.
  Device OpenCL C version:			 OpenCL C 1.2 
  Driver version:				 1124.2
  Profile:					 FULL_PROFILE
  Version:					 OpenCL 1.2 AMD-APP (1124.2)
  Extensions:					 cl_khr_fp64 cl_amd_fp64 cl_khr_global_int32_base_atomics cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomics cl_khr_3d_image_writes cl_khr_byte_addressable_store cl_khr_gl_sharing cl_ext_atomic_counters_32 cl_amd_device_attribute_query cl_amd_vec3 cl_amd_printf cl_amd_media_ops cl_amd_media_ops2 cl_amd_popcnt 


  Device Type:					 CL_DEVICE_TYPE_GPU
  Device ID:					 4098
  Board name:					 
  Device Topology:				 PCI[ B#5, D#0, F#0 ]
  Max compute units:				 24
  Max work items dimensions:			 3
    Max work items[0]:				 256
    Max work items[1]:				 256
    Max work items[2]:				 256
  Max work group size:				 256
  Preferred vector width char:			 16
  Preferred vector width short:			 8
  Preferred vector width int:			 4
  Preferred vector width long:			 2
  Preferred vector width float:			 4
  Preferred vector width double:		 2
  Native vector width char:			 16
  Native vector width short:			 8
  Native vector width int:			 4
  Native vector width long:			 2
  Native vector width float:			 4
  Native vector width double:			 2
  Max clock frequency:				 880Mhz
  Address bits:					 32
  Max memory allocation:			 268435456
  Image support:				 Yes
  Max number of images read arguments:		 128
  Max number of images write arguments:		 8
  Max image 2D width:				 16384
  Max image 2D height:				 16384
  Max image 3D width:				 2048
  Max image 3D height:				 2048
  Max image 3D depth:				 2048
  Max samplers within kernel:			 16
  Max size of kernel argument:			 1024
  Alignment (bits) of base address:		 2048
  Minimum alignment (bytes) for any datatype:	 128
  Single precision floating point capability
    Denorms:					 No
    Quiet NaNs:					 Yes
    Round to nearest even:			 Yes
    Round to zero:				 Yes
    Round to +ve and infinity:			 Yes
    IEEE754-2008 fused multiply-add:		 Yes
  Cache type:					 None
  Cache line size:				 0
  Cache size:					 0
  Global memory size:				 1073741824
  Constant buffer size:				 65536
  Max number of constant args:			 8
  Local memory type:				 Scratchpad
  Local memory size:				 32768
  Kernel Preferred work group size multiple:	 64
  Error correction support:			 0
  Unified memory for Host and Device:		 0
  Profiling timer resolution:			 1
  Device endianess:				 Little
  Available:					 Yes
  Compiler available:				 Yes
  Execution capabilities:				 
    Execute OpenCL kernels:			 Yes
    Execute native function:			 No
  Queue properties:				 
    Out-of-Order:				 No
    Profiling :					 Yes
  Platform ID:					 0x00007f10e6101520
  Name:						 Cayman
  Vendor:					 Advanced Micro Devices, Inc.
  Device OpenCL C version:			 OpenCL C 1.2 
  Driver version:				 1124.2
  Profile:					 FULL_PROFILE
  Version:					 OpenCL 1.2 AMD-APP (1124.2)
  Extensions:					 cl_khr_fp64 cl_amd_fp64 cl_khr_global_int32_base_atomics cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomics cl_khr_3d_image_writes cl_khr_byte_addressable_store cl_khr_gl_sharing cl_ext_atomic_counters_32 cl_amd_device_attribute_query cl_amd_vec3 cl_amd_printf cl_amd_media_ops cl_amd_media_ops2 cl_amd_popcnt 


  Device Type:					 CL_DEVICE_TYPE_CPU
  Device ID:					 4098
  Board name:					 
  Max compute units:				 8
  Max work items dimensions:			 3
    Max work items[0]:				 1024
    Max work items[1]:				 1024
    Max work items[2]:				 1024
  Max work group size:				 1024
  Preferred vector width char:			 16
  Preferred vector width short:			 8
  Preferred vector width int:			 4
  Preferred vector width long:			 2
  Preferred vector width float:			 8
  Preferred vector width double:		 4
  Native vector width char:			 16
  Native vector width short:			 8
  Native vector width int:			 4
  Native vector width long:			 2
  Native vector width float:			 8
  Native vector width double:			 4
  Max clock frequency:				 4046Mhz
  Address bits:					 64
  Max memory allocation:			 4183290880
  Image support:				 Yes
  Max number of images read arguments:		 128
  Max number of images write arguments:		 8
  Max image 2D width:				 8192
  Max image 2D height:				 8192
  Max image 3D width:				 2048
  Max image 3D height:				 2048
  Max image 3D depth:				 2048
  Max samplers within kernel:			 16
  Max size of kernel argument:			 4096
  Alignment (bits) of base address:		 1024
  Minimum alignment (bytes) for any datatype:	 128
  Single precision floating point capability
    Denorms:					 Yes
    Quiet NaNs:					 Yes
    Round to nearest even:			 Yes
    Round to zero:				 Yes
    Round to +ve and infinity:			 Yes
    IEEE754-2008 fused multiply-add:		 Yes
  Cache type:					 Read/Write
  Cache line size:				 64
  Cache size:					 32768
  Global memory size:				 16733163520
  Constant buffer size:				 65536
  Max number of constant args:			 8
  Local memory type:				 Global
  Local memory size:				 32768
  Kernel Preferred work group size multiple:	 1
  Error correction support:			 0
  Unified memory for Host and Device:		 1
  Profiling timer resolution:			 1
  Device endianess:				 Little
  Available:					 Yes
  Compiler available:				 Yes
  Execution capabilities:				 
    Execute OpenCL kernels:			 Yes
    Execute native function:			 Yes
  Queue properties:				 
    Out-of-Order:				 No
    Profiling :					 Yes
  Platform ID:					 0x00007f10e6101520
  Name:						 Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz
  Vendor:					 GenuineIntel
  Device OpenCL C version:			 OpenCL C 1.2 
  Driver version:				 1124.2 (sse2,avx)
  Profile:					 FULL_PROFILE
  Version:					 OpenCL 1.2 AMD-APP (1124.2)
  Extensions:					 cl_khr_fp64 cl_amd_fp64 cl_khr_global_int32_base_atomics cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomics cl_khr_int64_base_atomics cl_khr_int64_extended_atomics cl_khr_3d_image_writes cl_khr_byte_addressable_store cl_khr_gl_sharing cl_ext_device_fission cl_amd_device_attribute_query cl_amd_vec3 cl_amd_printf cl_amd_media_ops cl_amd_media_ops2 cl_amd_popcnt 

drivers exist

/dev/ati/
crw-rw-rw- 1 root root 250, 0 Nov 10 10:50 card0
crw-rw-rw- 1 root root 250, 1 Nov 10 10:51 card1
crw-rw-rw- 1 root root 250, 2 Nov  6 03:03 card2

Both of the cards (2gpu) and the (1gpu) working outside of boinc with no problem. Boinc is having a problem detecting and using both cards at the same time.

* 0. 03:00.0 AMD Radeon HD 6900 Series  
  1. 04:00.0 AMD Radeon HD 6900 Series  
  2. 05:00.0 AMD Radeon HD 6900 Series

* - Default adapter

boinc uses the first master card which is dual 6900 gpus and ignores the other one which is 1 6900 gpu. I assume as I've enabled the use all gpus it should use all the cards.

Do you have Monitors, or Dummy plugs attached to the second and third GPUs? According to Clinfo, only two of your GPUs are detected,

What does Boinc 7.2.28 detect? There has been many fixes since Boinc 7.0.65, I expect it should detect an extra GPU, but not the third.

Claggy

Thanks Claggy for the quick reply. I figured it out now boinc reports and uses all gpus

[---] CAL: ATI GPU 0: AMD Radeon HD 6900 series (Cayman) (CAL version 1.4.1741, 2048MB, 1919MB available, 6758 GFLOPS peak)
[---] CAL: ATI GPU 1: AMD Radeon HD 6900 series (Cayman) (CAL version 1.4.1741, 2048MB, 1993MB available, 6758 GFLOPS peak)
[---] CAL: ATI GPU 2: AMD Radeon HD 6900 series (Cayman) (CAL version 1.4.1741, 2048MB, 1993MB available, 6758 GFLOPS peak)
[---] OpenCL: AMD/ATI GPU 0: AMD Radeon HD 6900 series (Cayman) (driver version 1124.2, device version OpenCL 1.2 AMD-APP (1124.2), 2048MB, 1919MB available, 6758 GFLOPS peak)
[---] OpenCL: AMD/ATI GPU 1: AMD Radeon HD 6900 series (Cayman) (driver version 1124.2, device version OpenCL 1.2 AMD-APP (1124.2), 2048MB, 1993MB available, 6758 GFLOPS peak)
[---] OpenCL: AMD/ATI GPU 2: AMD Radeon HD 6900 series (Cayman) (driver version 1124.2, device version OpenCL 1.2 AMD-APP (1124.2), 2048MB, 1993MB available, 6758 GFLOPS peak)
[---] Config: use all coprocessors

It was a misconfiguration in X I just fixed the problem and now using all adapters. Thanks!