CPC bus tests

[arnoldemu]

Does that prove there's a floating bus? Or are the values just being left in some CPU register than didn't change? A floating bus would give random results, not known results.

Bryce.

The values seem stable on this 464, so in this case the values are not floating. It does seem to indicate that nothing is asserting the bus and the last read byte is the one that is seen, at least on plus. I am planning another test, where I start to execute from a known register value and let it go into unassigned asic register page, and see what happens, I hope eventually it'll end up executing some garbage as the data drops away.

I'll try the tests (excluding the asic register page one ) on a few other cpcs today and see what happens.

[arnoldemu]

So far it looks to only do it this way on Amstrad Plus.

Tested on:
464 with costdown and 6128 with type 0, both show ff for all values read. Same test.