Clarification of previous review

As a reader of this book and a user of Impulse C I feel that I should clarify some of the previous reviewer's comments. While "weirdweird" is clearly knowledgeable about FPGAs, he (or she) is confused about the programming and execution model used by Impulse C.

Impulse C is an extension to the traditional ANSI C programming language that permits development of FPGA hardware by writing C. Like any C-to-gates development tool, the resulting hardware design is inferior to what an experienced hardware designer could produce. However, many feel that the greatly reduced development time and effort of a C development environment is worth the performance trade-off. In many cases the resulting hardware runs significantly faster than software programs on a PC.

The CoDeveloper tools that come with Impulse C (they are not included with the book) compile C to FPGA hardware and, in the process, extract multiple types of parallelism. Contrary to what "weirdweird" says, the resulting designs do not suffer from traditional processor bottlenecks as the resulting designs are nothing like a processor. Hardware synthesized from Impulse C programs consists of a datapath controlled by a Finite State Machine, the same structure used in most hardware designs and one that is not found in processors.

In addition to any parallelism the user specifies through stream declarations, the Impulse C compiler can also perform loop unrolling and other optimizations to perform multiple operations in parallel. The tools also permit the simultaneous use of multiple memories internal to the FPGA, eliminating the "memory wall" to which the previous reviewer refers.

"weirdweird" is correct that this book focuses solely on Impulse C, so readers without potential access to the Impulse C tools might want to consider other choices.

Other Reviews

• Don't be fooled by the title
• Clarification of previous review
• Very mixed