You mentioned in your link:
"As I mentioned before, it’s important to make sure that the 34-pin cable connector doesn’t have the small plastic tab at the top"
This my issue .... "the small plastic tab at the top" .... now ... everything is perfect.
Thanks a lot ... really ... this is an amazing post... and marvelous link.
Yes. This interface has a known design mistake: it uses the frame-0 to access the FDC registers. It was a cost cutting decision to simplify the I/O decoder. This also has potential to give trouble in certain computers with unusual subROMs.
My idea was to redesign the interface:
1) Place the FDC registers in the correct 7FF0 region, thus fixing the design mistake
2) Add built-in Nextor support
3) Replace the EPROM with a Flash to allow easy Nextor updates
4) Add Disk-change signal support, so it can behave like the Turbo-R built-in interface when regarding to disk buffers/cache
5) Publish the FDC driver source so anyone who's experienced in FDC programming could add 1.44MB disk support
The problem is: I'm not having enough free time for that. So the project stays in the shelf.
Because MSX Audio BIOS install a handle for it's "MUSIC BIOS" which reside at that spot and somewhat hijacks the computer interrupts (similar like the MSX2 subrom does).