title: CUDA threads per block limitation
body: <p>Why I can't use max of <code>Max dimension size of a thread block (x,y,z): (1024, 1024, 64)</code>? If I use <code>(1024, 1024)</code> it doesn't work, and when I use <code>(32, 32)</code> or <code>(1, 1024)</code> etc. it works. Is it about shared memory?</p>
  
  <p>Here is my result from deviceQuery:</p>
  
  <pre><code>./deviceQuery Starting...
  
   CUDA Device Query (Runtime API) version (CUDART static linking)
  
  Detected 3 CUDA Capable device(s)
  
  Device 0: "Tesla M2070"
    CUDA Driver Version / Runtime Version          5.5 / 5.5
    CUDA Capability Major/Minor version number:    2.0
    Total amount of global memory:                 5375 MBytes (5636554752 bytes)
    (14) Multiprocessors, ( 32) CUDA Cores/MP:     448 CUDA Cores
    GPU Clock rate:                                1147 MHz (1.15 GHz)
    Memory Clock rate:                             1566 Mhz
    Memory Bus Width:                              384-bit
    L2 Cache Size:                                 786432 bytes
    Maximum Texture Dimension Size (x,y,z)         1D=(65536), 2D=(65536, 65535), 3D=(2048, 2048, 2048)
    Maximum Layered 1D Texture Size, (num) layers  1D=(16384), 2048 layers
    Maximum Layered 2D Texture Size, (num) layers  2D=(16384, 16384), 2048 layers
    Total amount of constant memory:               65536 bytes
    Total amount of shared memory per block:       49152 bytes
    Total number of registers available per block: 32768
    Warp size:                                     32
    Maximum number of threads per multiprocessor:  1536
    Maximum number of threads per block:           1024
    Max dimension size of a thread block (x,y,z): (1024, 1024, 64)
    Max dimension size of a grid size    (x,y,z): (65535, 65535, 65535)
    Maximum memory pitch:                          2147483647 bytes
    Texture alignment:                             512 bytes
    Concurrent copy and kernel execution:          Yes with 2 copy engine(s)
    Run time limit on kernels:                     No
    Integrated GPU sharing Host Memory:            No
    Support host page-locked memory mapping:       Yes
    Alignment requirement for Surfaces:            Yes
    Device has ECC support:                        Enabled
    Device supports Unified Addressing (UVA):      Yes
    Device PCI Bus ID / PCI location ID:           6 / 0
    Compute Mode:
       &lt; Default (multiple host threads can use ::cudaSetDevice() with device simultaneously) &gt;
  
  Device 1: "Tesla M2070"
    CUDA Driver Version / Runtime Version          5.5 / 5.5
    CUDA Capability Major/Minor version number:    2.0
    Total amount of global memory:                 5375 MBytes (5636554752 bytes)
    (14) Multiprocessors, ( 32) CUDA Cores/MP:     448 CUDA Cores
    GPU Clock rate:                                1147 MHz (1.15 GHz)
    Memory Clock rate:                             1566 Mhz
    Memory Bus Width:                              384-bit
    L2 Cache Size:                                 786432 bytes
    Maximum Texture Dimension Size (x,y,z)         1D=(65536), 2D=(65536, 65535), 3D=(2048, 2048, 2048)
    Maximum Layered 1D Texture Size, (num) layers  1D=(16384), 2048 layers
    Maximum Layered 2D Texture Size, (num) layers  2D=(16384, 16384), 2048 layers
    Total amount of constant memory:               65536 bytes
    Total amount of shared memory per block:       49152 bytes
    Total number of registers available per block: 32768
    Warp size:                                     32
    Maximum number of threads per multiprocessor:  1536
    Maximum number of threads per block:           1024
    Max dimension size of a thread block (x,y,z): (1024, 1024, 64)
    Max dimension size of a grid size    (x,y,z): (65535, 65535, 65535)
    Maximum memory pitch:                          2147483647 bytes
    Texture alignment:                             512 bytes
    Concurrent copy and kernel execution:          Yes with 2 copy engine(s)
    Run time limit on kernels:                     No
    Integrated GPU sharing Host Memory:            No
    Support host page-locked memory mapping:       Yes
    Alignment requirement for Surfaces:            Yes
    Device has ECC support:                        Enabled
    Device supports Unified Addressing (UVA):      Yes
    Device PCI Bus ID / PCI location ID:           20 / 0
    Compute Mode:
       &lt; Default (multiple host threads can use ::cudaSetDevice() with device simultaneously) &gt;
  
  Device 2: "Tesla M2070"
    CUDA Driver Version / Runtime Version          5.5 / 5.5
    CUDA Capability Major/Minor version number:    2.0
    Total amount of global memory:                 5375 MBytes (5636554752 bytes)
    (14) Multiprocessors, ( 32) CUDA Cores/MP:     448 CUDA Cores
    GPU Clock rate:                                1147 MHz (1.15 GHz)
    Memory Clock rate:                             1566 Mhz
    Memory Bus Width:                              384-bit
    L2 Cache Size:                                 786432 bytes
    Maximum Texture Dimension Size (x,y,z)         1D=(65536), 2D=(65536, 65535), 3D=(2048, 2048, 2048)
    Maximum Layered 1D Texture Size, (num) layers  1D=(16384), 2048 layers
    Maximum Layered 2D Texture Size, (num) layers  2D=(16384, 16384), 2048 layers
    Total amount of constant memory:               65536 bytes
    Total amount of shared memory per block:       49152 bytes
    Total number of registers available per block: 32768
    Warp size:                                     32
    Maximum number of threads per multiprocessor:  1536
    Maximum number of threads per block:           1024
    Max dimension size of a thread block (x,y,z): (1024, 1024, 64)
    Max dimension size of a grid size    (x,y,z): (65535, 65535, 65535)
    Maximum memory pitch:                          2147483647 bytes
    Texture alignment:                             512 bytes
    Concurrent copy and kernel execution:          Yes with 2 copy engine(s)
    Run time limit on kernels:                     No
    Integrated GPU sharing Host Memory:            No
    Support host page-locked memory mapping:       Yes
    Alignment requirement for Surfaces:            Yes
    Device has ECC support:                        Enabled
    Device supports Unified Addressing (UVA):      Yes
    Device PCI Bus ID / PCI location ID:           17 / 0
    Compute Mode:
       &lt; Default (multiple host threads can use ::cudaSetDevice() with device simultaneously) &gt;
  &gt; Peer access from Tesla M2070 (GPU0) -&gt; Tesla M2070 (GPU1) : No
  &gt; Peer access from Tesla M2070 (GPU0) -&gt; Tesla M2070 (GPU2) : No
  &gt; Peer access from Tesla M2070 (GPU1) -&gt; Tesla M2070 (GPU1) : No
  &gt; Peer access from Tesla M2070 (GPU1) -&gt; Tesla M2070 (GPU2) : Yes
  &gt; Peer access from Tesla M2070 (GPU1) -&gt; Tesla M2070 (GPU0) : No
  &gt; Peer access from Tesla M2070 (GPU1) -&gt; Tesla M2070 (GPU1) : No
  &gt; Peer access from Tesla M2070 (GPU2) -&gt; Tesla M2070 (GPU0) : No
  &gt; Peer access from Tesla M2070 (GPU2) -&gt; Tesla M2070 (GPU1) : Yes
  
  deviceQuery, CUDA Driver = CUDART, CUDA Driver Version = 5.5, CUDA Runtime Version = 5.5, NumDevs = 3, Device0 = Tesla M2070, Device1 = Tesla M2070, Device2 = Tesla M2070
  Result = PASS
  </code></pre>