What more i can do?

[m k]

Here are the Address and Data pictures of the first 20us for the working machine.
The first address is 3FFF8h.
The comparison for non-working machine I will make next.

My guess is that your address is one off.
A0 is actually A1 and real A0 is not present.
So ROM address for boot goes to correct address 7FFF0.

A bit after first jump is IN 35h.
Pictured A4 is dropping down after a jump and single high is 35h.

Jump address is F800, so A11 stays up.
35h has A5 and A4 up and A0 is missing.

[m k]

Working Board Address Inputs Wa0-Wa9

If you like you can check that A4 of all faulty boards.
If shape is the same you have functioning connection between CPU and program ROM.

If that single high is not there you have a similar fault that the original test subject has.

[222Lab_Test222]

Why did you scope only half of the data?

Half the data mean?

[222Lab_Test222]

If you like you can check that A4 of all faulty boards.
If shape is the same you have functioning connection between CPU and program ROM.

If that single high is not there you have a similar fault that the original test subject has.

If I do not get similar signals then that hints CPU is faulty?
Or is there any way to know CPU is ok or not.

[asis]

Hi,

If you have time, check the circuit by ringing the connections.
Please.
-
Next step will be - FRAM/ DRAM SIMM72.

[Shock]

I read this and I thought hmm beep only on a working board and I immediately thought a case opened tamper switch. I'd laugh if they are all working but a few aren't.

[222Lab_Test222]

Hi,

If you have time, check the circuit by ringing the connections.
Please.
-
Next step will be - FRAM/ DRAM SIMM72.

There is no direct connection between CPU and BIOS. there seems to buffer IC between them.
Please check Reply #283 and #275.
If you do not understand the connection let me know.

Note: here looks like IC 10 11 12 13 acts as a bridge between data pins of BIOS and CPU.

[asis]

Ok
I got that, but I don't see the type 10,11,12,13.
74LS245L x 4pcs?
-
I'll fix it.
Tnx.

[222Lab_Test222]

Ok
I got that, but I don't see the type 10,11,12,13.
74LS245L x 4pcs?
-
I'll fix it.
Tnx.

They are on back side of PCB. Here is the image.

[222Lab_Test222]

Time for New Year Break

be back again in a week

Happy New Year All

[Swake]

You too, and also for everyone here, have a perfect 2025 !

[m k]

Why did you scope only half of the data?

Half the data mean?

D0 to D7 only once.
So it was like #382?

First bigger interference of #477 means the start.
So first D0 is up, so 0d0d.
76543210
00001101

But the end part is very different than #382.
So one more time, with three sets you can start voting.

If you like you can check that A4 of all faulty boards.
If shape is the same you have functioning connection between CPU and program ROM.

If that single high is not there you have a similar fault that the original test subject has.

If I do not get similar signals then that hints CPU is faulty?
Or is there any way to know CPU is ok or not.

You can't prove negative.
CPU is also so complex that you can have a faulty section even when the thing seems to be ok.
One example is memory test, back in the day it was doomed to be inaccurate and only accurate thing being an operating system.
And even then it was still like which end or something in between.

Internal CPU errors are rare, like one day adding doesn't go anymore.
Usual problem area is external world interfacing part.
New processors with embedded extras are different.

So in practice you must diagnose enough faulty pins by judging them as not right, so comparing them with known good state.
But your CPU is regular and it is socketed, so "just" find an old regular computer and test them.
Digging the chip out is not necessary easy, check few videos.

In this case you can also use measurements, since that earlier wrong data was 0d0d and other ROM content is 0d, you can make an educated guess.
You swap ROMs and do the same measurement again.
But since you don't know what you don't know there are no short cuts, partial measurement doesn't tell much, you must do it all again.
Don't hassle either, be sure that chips are correctly inserted and legs are straight.

With old and new measurement you can do a comparison.
If the data is still 0d0d you can guess that it is not from a ROM at all.
If it is e9e9 you can guess that it is from the swapped ROM, and this can affect CPU operation in measurable way.
Since e9 is a jump you must have addresses measured also, so that you can check how that jump is executed.
If that jumped address then correlates to next data bytes you can say that the CPU is actually seeing what you have measured.
If jump address is something else you can do the next educated guess.

[asis]

next...