Follow the logic, it is the most important thing here:
First we found where the Bios itself is located. It turned out that it is in EPROM together with MS-DOS system.
We checked whether it loads - it turned out that it doesn't. It doesn't even try.
It became clear that the malfunction occurs at the very start. In modern machines, when the machine is turned on, a special Power On Sequence testing procedure occurs and it is quite complex (see the picture). We also have some events from this procedure.
On the other hand, we approached it from the other side, not head-on. We tried to understand which elements can cause such a multiple malfunction.
These are capacitors. CMOS with power supply that could run down and "spoil the data". Such cases have repeatedly occurred when the computer refused to start with a black screen due to a dead battery.
We checked the RTC that is the only one powered here. We found that the working one board has no pulses at the output, but the faulty one does.
Here. The faulty one starts from zero. The C0, C1, C2 pins have a low level, the output frequency is 64 Hz according to the datasheet (Correction: C2 should be high!)
RTC on the working one board does not start from the zero. Now it stores the C'(0...3) settings recorded during the previous work cycle. Therefore TP (Timing Pulse) outputs are different.
But when you unsoldered the TP pin from the line, we were convinced that the TP signal does not affect the start.
Now about the important thing. I missed your message that "DATA OUT pin (Pin 10) is unstable in non working board", most likely this is interference on the bus in the Z state (high impedance). But the absence of CLK on pin 9 needs to be studied in more detail. Where does it come from?
PS
I remind everyone that we can't work faster because of the big time difference. It's like driving a Mars rover. From 3 to 20 minutes, radio waves fly in only one direction.