This paper tries to explain the rationales of two different key infrastructures of Real Time Abstraction Interface (RTAI): Real Time Hardware Abstraction Layer (RTHAL) and Adaptive Domain Environment for Operating Systems (ADEOS), and also makes a comparison with measurement to help understanding the difference between them. Our study shows that ADEOS as a virtual resource layer can intercept hardware interrupts like RTHAL which is essentially just a data structure. And through measurement, we found that both the RTHALbased RTAI and the ADEOS-based RTAI offer maximum scheduling latencies in microseconds, while latencies of the latter are all slightly greater than those of the former under different situations. However, these differences are so trivial that ADEOS can be competent to replace RTHAL for RTAI. Moreover, ADEOS can help RTAI solve the patent problem with RTLinux, so it has already replaced RTHAL since RTAI 3.0 actually.