  The performance of discrete general purpose graphics processing units
(GPGPUs) has been improving at a rapid pace. The PCIe interconnect that
controls the communication of data between the system host memory and the GPU
has not improved as quickly, leaving a gap in performance due to GPU downtime
while waiting for PCIe data transfer. In this article, we explore two
alternatives to the limited PCIe bandwidth, NVIDIA NVLink interconnect, and
zero-copy algorithms for shared memory Heterogeneous System Architecture (HSA)
devices. The OpenCL SHOC benchmark suite is used to measure the performance of
each device on various scientific application kernels.
