Hacker News Reader

Separate ARM SOC in Apple laptops always puzzled me. Does anyone know why it's there?

Which component? I imagine these are for all of the little things that need GPIO, like power and under-keyboard lights, the lid close sensor, etc. There's no use powering up the main CPU to slowly strobe the power light at you when you can offload that to a component that sips power.

The little fading lights aren't actually using any CPU. It's just PWM: http://en.wikipedia.org/wiki/Pulse-width_modulation

The extra ARM cores tend to be integrated into 802.11 controllers or storage controllers.

>Which component?

Cypress Semiconductor CY8C24794-24LTXI Programmable System-on-Chip

If you look at the datasheet for that component[1] you'll see that it's actually a really slow (24MHz) "M8C" core, which turns out to be a MIPS core[2]. It's got a ton of GPIO and various other interfaces (I2C, SPI, serial) as well as USB. I would bet that that chip drives a bunch of the little stuff.

[1]: http://www.cypress.com/?mpn=CY8C24794-24LTXI

[2]: http://eessential.blogspot.com/2010/11/survey-of-microcontro...

Reply on news.ycombinator.com