Opinion on Zaidi et al. US '126:

Reviewed Zaidi et al. US '126 in response to EE Times article at: http://www.eet.com/semi/news/OEG20030801S0043 None of the standard WISHBONE SoC interconnections (i.e. point-to-point, shared bus or crossbar) meet the specifications of Zaidi et al. Claim 1 (e.g. no p-bus or m-bus). All the other claims are dependent on Claim 1, and so are irrelevant. Therefore, WISHBONE does not infringe on this patent because it does not meet the claim specifications.

One interesting goal of the invention is to make chip systems "portable between silicon foundries" (Col. 3, Line 11). The combined specifications of Claim 1 and Claim 2 appear to achieve this with a novel invention combining off-the-shelf ASIC System-on-Chip technology with portable multiplexer buses a la WISHBONE. This is a useful improvement because it allows them to move their System-on-Chip from ASIC devices to FPGA devices in a portable manner.

The EE Times article stresses the multiplexer logic element of Claim 2. While this is certainly key to their invention, it is not the only thing that must be done to infringe on the patent. Claim 1 of the patent requires a combination of many elements...only one of which is a multiplexor interconnection.

Multiplexer logic interconnections for SoC weren't novel at the time of Zaidi's provisional filing on 20 Jan 2000. At that time Silicore had already used mux logic for the same purpose, and had known about this simple technique for quite some time. Prior art stressing the portability benefits of mux logic was publicly available on the Silicore website at www.silicore.net/wishbone.htm. This fact was double checked by pulling WISHBONE FAQ pages and files from Silicore's backup files dated 10 Jan 2000, which are made available here in the archive file named: WISHBONE_1999.zip. Examples are located at: WISHBONE Spec Rev A (footnote at bottom of page 4); also application note WBAN003 (see pages 5 & 6).

Comments on this opinion are welcome, and should be directed to: wadep@silicore.net

WD Peterson - 5 Oct 2003

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