Linked by Thom Holwerda on Tue 12th Nov 2013 23:06 UTC
PDAs, Cellphones, Wireless

I've always known this, and I'm sure most of you do too, but we never really talk about it. Every smartphone or other device with mobile communications capability (e.g. 3G or LTE) actually runs not one, but two operating systems. Aside from the operating system that we as end-users see (Android, iOS, PalmOS), it also runs a small operating system that manages everything related to radio. Since this functionality is highly timing-dependent, a real-time operating system is required.

This operating system is stored in firmware, and runs on the baseband processor. As far as I know, this baseband RTOS is always entirely proprietary. For instance, the RTOS inside Qualcomm baseband processors (in this specific case, the MSM6280) is called AMSS, built upon their own proprietary REX kernel, and is made up of 69 concurrent tasks, handling everything from USB to GPS. It runs on an ARMv5 processor.

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RE: based on OKL4
by fuckregistration on Wed 13th Nov 2013 23:32 UTC in reply to "based on OKL4"
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"As far as I know, this baseband RTOS is always entirely proprietary."

Not "entirely" proprietary. Qualcomm's AMSS is based on OKL4, whose source code is available:

I remember being able to download the sourcecode from the same OKL4 version on which the AMSS of a phone of mine was based.

The OS is only a small portion of the code that runs in the baseband, though.

Great. That's the same relationship as with Darwin and Apple iOS. That gets you absolutely nothing, it's just a microkernel.

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