GAMMA on DEC 2114x with Efficient Flow Control

GAMMA is a prototype light-weight communication system based on the Active Ports paradigm, designed for efficient implementation over Fast Ethernet interconnects. The original implementation started in 1996 based on 3Com 3C595 cards. The optimizations obtained on that NICs allowed us to obtain the lowest latency and highest throughput results ever published in the literature for Fast Ethernet. Technology evolved, however, and now all low-cost NICs available are based on Descriptor Based DMA (DBDMA) transfers, originally introduced by the DEC chipset 21140. In this paper we report on the re-implementation of the GAMMA prototype for the DEC NICs exploiting the new transfer modes and achieving substantially equivalent performance figures. We also describe the addition of an efficient flow-control algorithm, that allows loss-free communications without seriously affecting performance. Keywords: Active Ports; Fast Ethernet; Low Latency; Descriptor Based DMA; Flow-control. 1 Introduction Li..