Keil CMSIS-RTOS:
Description Limitations
Defined Tasks Unlimited
Active Threads 250 max
Mailboxes Unlimited
Semaphores Unlimited
Mutexes Unlimited
Signals 16 per thread
Timer Callbacks Unlimited
Code Space < 5.0 Kbytes
RAM Space for Kernel 300 bytes + 128 bytes Main Stack
RAM Space for a Thread StackSize + 52 bytes
RAM Space for a Mailbox MaxMessages * 4 + 16 bytes
RAM Space for a Semaphore 8 bytes
RAM Space for a Mutex 12 bytes
RAM Space for a User Timer 20 bytes
Hardware Requirements SysTick timer or other hardware timer
Thread context switch time < 2.6 usec @ 72 MHz
Interrupt lockout time Not disabled
SafeRTOS http://www.highintegritysystems.com/safertos/rtos-features/Typical ROM Requirements 6-15kB.
Typical RAM Requirements 500 bytes.
Typical Stack Requirements 400 bytes/task.