An open-source HyperTransport core

This article presents the design of a generic HyperTransport (HT) core. HyperTransport is a packet-based interconnect technology for low-latency, high-bandwidth point-to-point connections. It is specially optimized to achieve a very low latency. The core has been verified in system using an FPGA. This exhaustive verification and the generic design allow the mapping to both ASICs and FPGAs. The implementation described in this work supports a 16-bit link width, as used by Opteron processors. On a Xilinx Virtex-4 FX60, the core supports a link frequency of 400 MHz DDR and offers a maximum bidirectional bandwidth of 3.2GB/s. The in-system verification has been performed using a custom FPGA board that has been plugged into a HyperTransport extension connector (HTX) of a standard Opteron-based motherboard. HTX slots in Opteron-based motherboards allow very high-bandwidth, low-latency communication, since the HTX device is directly connected to one of the HyperTransport links of the processor. Performance analysis shows a unidirectional payload bandwidth of 1.4GB/s and a read latency of 180 ns. The HT core in combination with the HTX board is an ideal base for prototyping systems and implementing FPGA coprocessors. The HT core is available as open source.