editor's blog
Subscribe Now

Big and Little Core Combos

A long while back ARM introduced their big.LITTLE concept. (So cute how they put the big in little letters and the little in big letters! Did you notice that?) The general concept is to have one beefy processor for heavy lifting and one small one for light duty; by powering them up and down, you can save energy by assigning the right core to the right task.

But at last week’s Multicore DevCon, processor guru Linley Gwennap showed, among other things, various ways in which companies are implementing this concept. Although, of course, ARM figures in all of them.

  • Nvidia includes an A15 CompanionCore (their original whitepaper shows an A9). Yeah, an A15 is the “little.” The point is that, unlike the other A15s on the chip, this one is optimized on the low-power end of the process, so it has less performance but consumes less power.
  • Samsung is going more the way ARM suggested: pairing an A15 with an A7. The A7 is 3.3 times more power efficient in MIPS/W; twice as efficient in MIPS/m2. But the A15 is 3 times faster.
  • Samsung’s Octa is more complicated. It has 4 A15s and 4 A7s, all software compatible so that any software can run on any of them. Problem is, Android is running on it, and, for now, Android doesn’t like mixtures of core types: it want’s homogeneous (apparently a future rev won’t). So you can’t run both sets of four cores at the same time. If you want performance, then you run the four A15s and the A7s are powered off; if you want to run with lower power, then you shut the A15s down and power up the A7s and run them. That’s where the software compatibility is critical.
  • Qualcomm fakes it, you might say. They have an A15, and they just clock it way down to save power. This is almost as effective as using an A7.

Clearly lots of ways to skin that cat…

Leave a Reply

featured blogs
Jun 18, 2018
Many years ago, when Nokia was at the top of its game'€”one in every three phones shipped was a Nokia'€”I chatted to the sister of a friend of mine who was something senior in Nokia finance. I think she was the controller for a good part of their Africa business. Since in...
Jun 14, 2018
Samtec has released the industry'€™s first 0.50 mm pitch edge card socket with justification beam. This design allows high-speed signals to pass through an incredibly dense connector while keeping the mating PCB at a reasonable cost. The socket'€™s justification beam is d...
Jun 7, 2018
If integrating an embedded FPGA (eFPGA) into your ASIC or SoC design strikes you as odd, it shouldn'€™t. ICs have been absorbing almost every component on a circuit board for decades, starting with transistors, resistors, and capacitors '€” then progressing to gates, ALUs...
May 24, 2018
Amazon has apparently had an Echo hiccup of the sort that would give customers bad dreams. It sent a random conversation to a random contact. A couple had installed numerous Alexa-enabled devices in the home. At some point, they had a conversation '€“ as couples are wont to...