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A 10 um rock flips the cart

I recently stumbled upon a wikipedia article about Rendition – a Silicon valley based company which flourished straight after its foundation but unfortunately existed only a few years before going downhill. What draws attention is the vigorous inverse of the company's growth which was triggered by a few transistors positioned at the wrong place and the wrong time. Let's have a look at an excerpt from the Wikipedia article – this paragraph was most likely edited by an insider as of the high level of detail.

From Wikipedia:

Rendition was one step behind other competitors coming to market at a pivotal time in the 3D PC graphics engines battle. The NVIDIA RIVA 128 came to market in late 1997. The V2100 saw first silicon in early 1997, but was late to sample due to a digital cell library bug necessitating a respin. Rendition used the libraries developed by SiArch (licensed through Synopsys at that time) for their digital logic synthesis. A critical section of circuitry happened to synthesize into a 3 input nor-gate driving a scanned flip-flop. Apparently this combination was never spiced (an accurate circuit simulation engine) by SiArch. The scan-flop had three passive transmission gate muxes driven by the three n-type transistors in the NOR3, all in series. The result of this was excessive resistance with a weak bus-hold cell, which ate into the allowable noise margin and violated the static discipline in good digital logic design. This manifests itself as an intermittent bug that is seen in the lab but not in high level behavioral or even RTL or gate-level simulations. This root cause was only determined after months of investigation, simulations, and test case development in the lab, which narrowed the problem to a very confined space. At that point, the chip was run live under a scanning electron microscope using the oscilloscope probe mode to find the problem net between the NOR3 gate and the scan-flop. The combination was then spiced and confirmed to be the culprit. Two full quarters were lost due to this bug. Despite these delays, the V2x00 shipped with fully conformant OpenGL and D3D drivers.

In conclusion: even a 10 um rock could flip the cart.

Date:Wed Feb 15 20:24:05 GMT 2018


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