the '51 is an excellent choice for most of what we discuss in this forum. However, there are posts like this one that try to make the '51 into something it is not. The fact is that what is discussed here is not RTOS which does not exist in any version for any processor but RFROS (reasonably fast response OS). I have been exposed to RFROS on other processors and projects (e.g. cellphones) where the RFROS was the right choice but for the applications for which the '51 is designed RFR is not good enough.

In other words, in my opinion, if you use a RFROS onm a '51 you are using the wrong processsor.

Erik