# uc/OS v/s freeRTOS

**URL:** <https://forums.freertos.org/t/uc-os-v-s-freertos/553>\
**Category:** Kernel\
**Created:** [November 10, 2004, 3:01pm UTC](https://forums.freertos.org/t/uc-os-v-s-freertos/553 "2004-11-10T15:01:50Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\
**Post date:** [November 10, 2004, 3:01pm UTC](https://forums.freertos.org/t/uc-os-v-s-freertos/553/1 "2004-11-10T15:01:50Z")

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**nobody** wrote on [Wednesday, November 10, 2004](https://sourceforge.net/p/freertos/discussion/382005/thread/19d901ca/#acb5):

how do we compare uc/OS with freeRTOS. I am interested only in reliability and performance. ie how good is the existing features of freeRTOS compared to the similar features offered by uc/OS

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**Author:** ![rtel](https://d3iykfbgfh8zhg.cloudfront.net/user_avatar/forums.freertos.org/rtel/32/31_2.png) [@rtel](https://forums.freertos.org/u/rtel)\
**Post date:** [November 11, 2004, 7:28am UTC](https://forums.freertos.org/t/uc-os-v-s-freertos/553/2 "2004-11-11T07:28:11Z")

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**[rtel](https://sourceforge.net/u/rtel/)** wrote on [Thursday, November 11, 2004](https://sourceforge.net/p/freertos/discussion/382005/thread/19d901ca/#acb5/3396):

Which is best depends on your application.&nbsp; The mechanics of using FreeRTOS and uCOS are very similar.

There are two main differences between the two:

1)&nbsp;&nbsp;&nbsp; Licensing.&nbsp; FreeRTOS is completely free for any application.&nbsp; The uCOS source code comes bundled with a book requiring purchase, and a binary run time license ($$$) is required if you use uCOS in a commercial application.

2)&nbsp;&nbsp;&nbsp; Scheduling.&nbsp; uCOS uses a bitmap scheduler, FreeRTOS does not.&nbsp; A bitmap scheduler has the advantage of allowing a more deterministic context switch time, and in some cases a faster context switch time&nbsp; it does however severely restrict your design freedom as it only allows a single task at any given priority level.&nbsp; FreeRTOS on the other hand is more flexible as any number of tasks can share the same priority.

I think FreeRTOS is simpler to use;&nbsp; initialization is automatic on creation of the first task, and ISR routines dont have to be written in assembler.&nbsp; But you are probably asking the wrong person if you want a non-biased opinion!

Regards.

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**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\
**Post date:** [December 2, 2004, 4:59pm UTC](https://forums.freertos.org/t/uc-os-v-s-freertos/553/3 "2004-12-02T16:59:24Z")

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**nobody** wrote on [Thursday, December 02, 2004](https://sourceforge.net/p/freertos/discussion/382005/thread/19d901ca/#acb5/6205):

another point is ports: ucos supports tens (hundreds) of MCUs while freertos is still starting up. also code quality has been proven by validation suites for ucos (e.g. FDA).

I wonder how well freertos covers a full range testsuite…?