NVIDIA CEO Jen-Hsun Huang publicly questioned the economic viability of the whole 20 nm node, saying that its cost per transistor might never drop below that of 28 nm.The 20 nm node is arguably the most difficult ever attempted for production, and just a description of the technical challenges would justify a small book.
Cost is paramount. NVIDIAs Huang may well have been right: with its greatly increased costs, 20 nm may always be more expensive than 28 nm for the same number of transistors.For SoCs with significant amounts of non-scaling circuitry, such as RF or other analog transistors, monolithic passive components, or electrostatic discharge protection structures, the gap will be larger than for dense logic-only SoCs. Quite simply, for an SoC to migrate to 20 nm, there will have to be some benefitintegration, performance, energy efficiency, or IP accessnot available at 28 nm. Otherwise there will be no way to justify the added cost. The Fine-Print Take Away
The ability to spend transistors to buy performance is absolutely vital to 20 nm SoCs for one simple reason: at the block level, 20 nm chips will not be much faster than their 28 nm equivalents. This is not immediately obvious from the publicity. TSMC, for example, claims that their 20 nm technology
can provide 30 percent higher speed
than its 28 nm technology. That is not the doubling we used to expect between process generations, but it is not trivial. Yet to achieve that speed on an entire block, rather than on a few critical paths, might require lavish use of low-Vt transistors with very significant leakage current, raising the issue of local-heating problems. Even without the thermal issues, the design might never close timing across all the many process, voltage, and temperature corners that 20 nm presents. Some engineers have suggested that taking power and variations into consideration, blocks simply ported to 20 nm may gain no speed at all.http://www.altera.co.uk/technology/system-design/articles/2012/20nm-systems-era.html You should probably post this for the KNC people that have pre-orders and huge money riding on 20NM coming in "april or may", if you think this is correct. It would seem those people need to decide for themselves if 20NM is ever coming (considering 3600 X $10,000 worth of 20NM KNCs have been pre-sold)