PCem

I have noticed that time synchronize depends on the emulation speed.

With a Pentium 75 (which I emulate at 100%) I get a 2-3 seconds delay from host, but with no increase.
With a Pentium 200 (62% emulation speed) I get a 10 seconds delay increase every minute.

Is this the expected behavior?

I have the synchronize time to host clock active.

It is perfectly expected. A lower than 100% emulation speed means that the emulated machine is going slower than realtime, so it takes more time to do the same (like increasing one second).

In other words, your machine is not capable of emulating a Pentium 200 with PCem.