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README.md: update features #18777

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21 changes: 14 additions & 7 deletions README.md
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Expand Up @@ -55,25 +55,32 @@ LGPL code.

## FEATURES

RIOT is based on a microkernel architecture, and provides features including,
but not limited to:
Comment on lines -58 to -59
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This may be a bit controversial. But I 100% agree that RIOT-OS is not and never has been using a micro kernel architecture.

I recall that Andrew Tanenbaum gave a relatively lax interpretation of what a microkernel architecture is. The absence of any MMU / MPU like feature, according to him, doesn't rule out that an OS does check the box of a microkernel architecture. If I recall correctly, he said that MINIX was developed initially on pre-MMU systems with the anticipation of an MMU, so that making use of the MMU to actually provide the benefits of a microkernel architecture was relatively easy.

However, we with RIOT are now in a situation that MPUs are there. Still, the effort to make use of it in a microkernel point of view (or even in a userspace vs kernelspace point of view) is still significant. To me, this is a good indicator that RIOT is not using a microkernel architecture, even with the relatively lax point of view that actual use of MMU (or MPU) is not needed for the claim.

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I guess we all agree this qualification is not 100% fitting, but after all these years, and after pitching it here & there (including to top experts such as Tanenbaum as recalled by @maribu) it seems it remains the best "single term" description for the arch. For a longer explanation (which does not really belong right here) we could maybe open a separate wikipage / doc entry on this, what do you think?

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What makes you think the arch is a microkernel? Having a hand-wavy explanation to claim something that is not true does not build trust. How would you react to a car salesman selling you an electric¹ car?

[1] lead acid battery used to start the internal combustion engine

RIOT provides features including, but not limited to:

* a preemptive, tickless scheduler with priorities
* flexible memory management
* high resolution, long-term timers
* support 100+ boards based on AVR, MSP430, ESP8266, ESP32, RISC-V,
* MTD abstraction layer
* File System integration
* support 200+ boards based on AVR, MSP430, ESP8266, ESP32, RISC-V,
ARM7 and ARM Cortex-M
* the native port allows to run RIOT as-is on Linux and BSD. Multiple
instances of RIOT running on a single machine can also be interconnected via
a simple virtual Ethernet bridge
* the native port allows to run RIOT as-is on Linux and BSD.
Multiple instances of RIOT running on a single machine can also be
interconnected via a simple virtual Ethernet bridge or via a simulated
IEEE 802.15.4 network (ZEP)
* IPv6
* 6LoWPAN (RFC4944, RFC6282, and RFC6775)
* UDP
* RPL (storing mode, P2P mode)
* CoAP
* OTA updates via SUIT
* MQTT
* USB (device mode)
* Display / Touchscreen support
* CCN-Lite
* Sigfox
* LoRaWAN
* UWB
* Bluetooth (BLE) via [NimBLE](https://github.com/apache/mynewt-nimble)

## GETTING RIOT

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