I have two MT5 installations on my server, the server has 8 xeon cores. On either MT5 insttalation I am not able to disable the first core in the Agents tab. I think this is a bug or wrong design!
My first MT5 install is running a huge optimization, I told it to use the first 6 cores, which it does. So on my second MT5 install it is not possible to disable the first 6 cores so the last 2 cores are used. only core 2 till 6 can be disable.