Chuck(G)
25k Member
No--I don't believe that the 8087 makes use of the mechanism. What I remember from the 80287 was that the memory access scheme used by the 8086 wasn't suitable for the protected-mode 80286 (think about the segmented memory model). The 80287 datasheet also says this:
The way I understand it, the 80286/80386 does all of the fetching and storing, rather than having the 80287 handle the bus (as it does with the 8087); data is passed via I/O and the 287 keeps track of the number of bytes transferred.
I/O ports 00F8H to OOFFH are reserved for the 80286/80287 interface. To guarantee correct operation of the 80287, programs must not perform any I/O operations to these ports.
The way I understand it, the 80286/80386 does all of the fetching and storing, rather than having the 80287 handle the bus (as it does with the 8087); data is passed via I/O and the 287 keeps track of the number of bytes transferred.