I have tested the "thread option" if you mean Global compiler settings | Build options | Number of processes for parallel builds
I get the expected number of cl.exe instances in Windows Task Manager.
If I set the number to 1, the build takes 5 minutes, i.e. slower than using the 2 processors I have. I get one cl.exe instance. If I set the number to 6, (3 times more than my 2 processors), I get 6 instances of cl.exe, the build then takes 2 minutes 42 seconds, about the same as when using 2 processors (no surprise).
So the problem is unrelated to the number of processor-setting. The problem is that, in 7966, something is preventing the compiler from using available CPU. During build with 7966, CPU use behaves like a yo-yo in Windows Task Manager, see attachment. The processors work at 100% for a while, then pauses for a significant period, where none of the cl.exe processes consume any CPU. This is totally different in 7452, where such pausing is not observed, compilation runs at full speed almost continuously. This is the reason why it is so much faster. The important question is what is causing the pausing in 7966, and I don't know the answer to that.
Another clue is perhaps this: When tweaking the setting Global compiler settings | Build options | Number of processes for parallel builds and press OK on 7452, the dialog disappears immediately. Again, it is different in 7966, where it takes almost 10 seconds from the time OK is pressed until the dialog disappears.
Btw. there is no antivirus or other "known nasties" running on the system. If that had been the problem, it shouldn't help to run an older C::B, but it does.
PS: Todo plugin (and many other plugins) disabled long time ago.