How to improve FPGA-based ASIC prototyping with SystemVerilog

By Roger Do, Mentor Graphics
pldesignline.com (October 29, 2008)

Introduction

ASICs provide a solution for capturing high performance complex design concepts and preventing competitors from simply implementing comparable designs.

However, creating an ASIC is a high-investment proposition with development costs approaching $20M for a 90 nm ASIC/SoC design and expected to top $40M for a 45 nm SoC. Thus, increasingly, only a high-volume product can afford an ASIC.

Besides the increase in mask-set cost, total development cost is also increasing due to the reduced probability of getting the design right the first time. As design complexity continues to increase, surveys have shown that only about a third of today's SoC designs are bug-free in first silicon, and nearly half of all respins are reported as being caused by functional logic error(s). As a result, verification managers are now exploring ways to strengthen their functional verification methodologies.

Before starting on a true ASIC design, to demonstrate that concepts are sound and that designs can be implemented, a lower-cost method of using FPGAs to prototype ASIC designs as part of an ASIC verification methodology has been growing in popularity.

Prototyping ASIC designs in FPGAs, while often yielding different performance, often results in the same logical functionality. Further, running a design at speed on an FPGA prototype with real stimulus allows for a far more exhaustive and realistic functional coverage as well as early integration with embedded software. Thus FPGA prototyping can be used effectively to supplement and extend existing functional verification methodologies.

As ASIC designs have grown larger at a much faster pace than FPGA devices, often multiple FPGA devices must be used to prototype a single ASIC. The obstacle of using multiple devices is the task of connecting all of the logical blocks of the ASIC design across multiple FPGA devices. Physically, with the use of the high speed I/O blocks in FPGA devices, connectivity between physical devices has been simplified. However, methods for logically connecting the design blocks have proven to be manually intensive and error prone. With the introduction of SystemVerilog, an evolutionary RTL language, and advanced mixed language synthesis tools such as Mentor Graphics' Precision Synthesis, the procedure for connection has also been simplified.

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