"The other kind of heterogeneity we have seen on the ARM side is general purpose processors but smaller, slower ones and larger, more powerful ones and moving the workloads around when there is more stuff to do - that is another area of interest [for Intel]. Obviously operating systems must help there. Most operating systems tend to think all the cores are the same, but [they are] not in that case," said Justin Rattner, chief technology officer of Intel, in a conversation with The Inquirer web-site.
There are a number of heterogeneous multi-core approaches that exist today, the best known two are accelerated processing units (which combine x86 processing engines, stream processors and fixed-function processing hardware) as well as system-on-chips (which include general-purpose processing engines, graphics processing engines, fixed-function hardware, custom hardware and input output capabilities). The main feature about the current heterogeneous chips is that they feature only one type of general-purpose cores; hence, they either offer great performance at the cost of higher power consumption, or they consume little power, but do not perform well in demanding applications.
One of today’s technology most significant challenges is how to create a system-on-chip (SoC) that meets the conflicting consumer demand for devices with both higher-performance and extended battery life. ARM’s Big.Little processing approach achieves this by pairing the best of the high-performance ARM Cortex-A15 MPCore and ultra-efficient ARM Cortex-A7 processors. Big.Little processing combines two different, but compatible processors within the same SoC and allows the power management software to seamlessly select the right processor, or multiple processors, for the right task. The efficient and seamless switching of workloads between the two processors is supported by advanced ARM system IP, such as AMBA 4 ACE coherency extensions, which ensures full cache, I/O and processor-to-processor coherency between the Cortex-A15 and Cortex-A7, and across the complete system. Software and applications can therefore continue to run unhindered, and unnoticed by the user, as the tasks are rebalanced to provide the optimum Big.Little user experience.
Unfortunately, mainstream operating systems like Microsoft Windows cannot seamlessly switch tasks from one core to another, which makes nearly impossible to release a chip that would contain Atom-architecture and a Core-architecture processing cores, including because of the fact that both support different instructions. Nonetheless, Intel does not seem to rule out a possibility for such a heterogeneous multi-core solution.