Of course there is a bottleneck, how can you know how a computer works and not know there is a bottleneck at the gpu-cpu interface??
SAN JOSE, CA - GTC -- NVIDIA today announced that it plans to integrate a high-speed interconnect, called NVIDIA® NVLink™, into its future GPUs, enabling GPUs and CPUs to share data five to 12 times faster than they can today.
This will eliminate a longstanding bottleneck and help pave the way for a new generation of exascale supercomputers that are
50-100 times faster than today's most powerful systems.
NVIDIA NVLink is the world's first high-speed GPU interconnect, helping pave the way to exascale computing.
NVIDIA will add NVLink technology into its Pascal GPU architecture -- expected to be introduced in 2016 -- following this year's new NVIDIA Maxwell compute architecture. The new interconnect was co-developed with IBM, which is incorporating it in future versions of its POWER CPUs.
Today's GPUs are connected to x86-based CPUs through the PCI Express (PCIe) interface, which limits the GPU's ability to access the CPU memory system and is four- to five-times slower than typical CPU memory systems. PCIe is an even greater bottleneck between the GPU and IBM POWER CPUs, which have more bandwidth than x86 CPUs. As the NVLink interface will match the bandwidth of typical CPU memory systems, it will enable GPUs to access CPU memory at its full bandwidth.
This high-bandwidth interconnect will dramatically improve accelerated software application performance. Because of memory system differences -- GPUs have fast but small memories, and CPUs have large but slow memories -- accelerated computing applications typically move data from the network or disk storage to CPU memory, and then copy the data to GPU memory before it can be crunched by the GPU. With NVLink, the data moves between the CPU memory and GPU memory at much faster speeds, making GPU-accelerated applications run much faster.
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