Design and Implementation of a 1.2 Gbit/s ATM Cell Buffer using a Synchronous DRAM Chip

by George N. Glykopoulos

Technical Report FORTH-ICS/TR-221
July 1998

Computer Architecture and VLSI Systems Division,
Institute of Computer Science (ICS), FORTH
Science and Technology Park of Crete, P.O.Box 1385, Heraklion, Crete, GR 711 10 Greece

Master of Science Thesis, Department of Computer Science, University of Crete

ABSTRACT

High speed networks require high throughput memories to store cells or packets. Synchronous Dynamic RAM (SDRAM) chips provide both high storage capacity and high throughput, and are thus an appropriate technology for building such cell or packet buffers. One 16Mbit SDRAM chip with a 16-bit data interface provides 40K cell storage and 1.2Gbit/s throughput when used as an ATM cell buffer.

The purpose of this work was to demonstrate this capability in a working prototype, gaining familiarity with the practical details of SDRAM and SONET operation, and PCB implementation with 100MHz clocks. The prototype that was designed, manufactured and successfully tested, is an 8-layer PCB with two SONET OC-3 links (2 x 155.52Mbit/s incoming and 2 x 155.52Mbit/s outgoing throughput), interfaced to an SDRAM chip using two ALTERA FPGA's. The board also includes a microprocessor interface and PLL-driven clock generators/drivers.

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