Thursday, May 28, 2020

Ruminating on Azure RTOS

Microsoft acquired ThreadX from Express Logic and re-branded it as Azure RTOS. ThreadX was already a popular RTOS that is being used by more than 6.5B devices worldwide.
** Gartner predicts that by 2021, one million new IoT devices will come online every hour of every day. In 2019, there were approx 27B IoT devices.

Besides ThreadX, Azure RTOS has also packaged other modules such as GuiX, FileX, NetX, USBX, etc. 

The below link points to an interesting conversation with Bill Lamie - founder of ThreadX. 

Jotting down some interesting points below. 
  • The most important characteristic of an RTOS is size. RTOS size is typically in KB, whereas general purpose OS is in MB or GB. Because of this size, RTOS can be used in the smallest of devices...even battery powered ones - e.g. fitness wearables, medical implants, etc. So essentially RTOS is great for constrained/smaller devices. 
  • RTOS is "real-time" because the OS responds to real time events in a deterministic time frame. An RTOS guarantees that certain actions can happen on IoT devices within defined time limits - a feature called as determinism. 
  • The size of Azure RTOS can scale down all the way to 2KB. A cloud connected RTOS would take 50KB.
  • Azure RTOS also brings in best-of-class security with multiple security certifications. 
  • The complete source code of Azure RTOS is open-source and available on GitHub at
Before the acquisition of Express Logic, Microsoft had an offering called Azure Sphere OS that was positioned as an OS for edge devices. Azure Sphere is more secure and is Linux kernel based, but cannot run on highly constrained devices. Also it has a Linux kernel and is not an RTOS and hence cannot provide deterministic execution. 

Though Microsoft is currently stating that Azure RTOS and Azure Sphere are complementary, only time will tell which OS the industry adopts. 

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