OpenComRTOS is one of the few Real-Time Operating Systems for embedded systems that was developed using formal modelling techniques. The goal was to obtain a proven dependable component with a clean architecture that delivers high performance on a wide variety of networked embedded systems, ranging from a single processor to distributed systems. The result is a scalable relibable communication system with real-time capabilities. Besides, a rigorous formal verification of the kernel algorithms led to an architecture which has several properties that enhance safety and real-time properties of the RTOS. The code size in particular is very small, typically 10 times less than a typical equivalent single processor RTOS. The small code size allows a much better use of the on-chip memory resources, which increases the speed of execution due to the reduction of wait states caused by the use of external memory. To this point we ported OpenComRTOS to the MicroBlaze processor from Xilinx, the Leon3 from ESA, the ARM Cortex-M3, the Melexis MLX16, and the XMOS. In this paper we concentrate on the Microblaze port, which is an environment where OpenComRTOS competes with a number of different operating systems, including the standard operating system Xilinx Micro Kernel. This paper reports code size figures of the OpenComRTOS on a MicroBlaze target. We found that this code size is considerably smaller compared with published code sizes of other operating systems.