Processing horsepower for the convergence of data streams: Page 3 of 6

temperature dependent – it doubles every 25 to 30 kelvins. So although leakage current in a smartphone at room temperature is still at a reasonable level, it can be ten times higher in an automotive environment and even exceed dynamic power consumption. A transistor needs to be designed for the maximum clock speed possible, yet fast transistors also tend to have high levels of leakage current. That is why it is becoming standard practice in chip design to use libraries of transistors at varying speeds. The fastest ones are only used if the design really requires them. A reduction in the highest clock speed to meet the application’s requirements plays a big part in reducing power consumption.

Renesas took all these issues into account when designing and developing the R-Car, its new, second-generation application processor family for automotive applications. The company made good use of its many years of chip design experience right from the outset. Renesas’ top priority for this product was to solve the performance vs. power conundrum – in other words, to double performance level while remaining true to its “Design for Power” strategy. Combining these two rather contradictory goals resulted in the need for a few optimisations.

In order to achieve the performance goals, Renesas developed the R-Car product using the latest 28nm process. This process enables the integration of roughly twice the number of transistors on the same chip surface compared to 40nm technology. Despite the smaller structure width, Renesas managed to keep leakage current at the same level while reducing dynamic losses by about 20 per cent per transistor.

Implementing the huge processing power of over 25,000 Dhrystone MIPS was only possible with the integration of an ARM Cortex A15 quad-core at 1.4 GHz. This quad-core is joined by another almost 800 MHz Cortex A7 quad-core, which helps out its bigger buddy by seamlessly taking on software-related tasks if it is not too busy