data on bus at interrupt time

[arnoldemu]

Hi,
I made a program that will detect the data on the data bus at interrupt time.
This runs on CPC and will detect all the data bytes seen when an interrupt is acknowledged.I would like this to be run on *CPC* only please.
On most CPCs it's normally 0x0ff. If you see a different value please tell me, if possible, the details written on the ICs inside your computer, specifically the CPU, CRTC, 8255, GA and the PCB version.I think there is a specific CPC setup that is causing this.
I am trying to resolve one of the last mysteries of the CPC where some computers do not have &ff on the bus.

Thank you.

(Technical:
I use interrupt mode 2.
I use a special pattern for the interrupt table which allows me to minimize the ram used to handle all possible values at interrupt time.
I use RST 38 and in the interrupt handler I capture the return address and then update a counter in another block of memory to say how many times I saw each address.
At the end, I then check the count and if it is not 0, I report the data byte that would have caused that address to be used.)

[roudoudou]

You mean, without any hardware plugged on the CPC ?

[arnoldemu]

You mean, without any hardware plugged on the CPC ?

Yes please.

[arnoldemu]

I am especially interested in results from CPCs with early model GA's (40007) - the ones with the metal cooling plates.
Thank you.