[Coco] megaread HOW TO ?

[William Astle]

On 2020-04-06 8:06 a.m., Allen Huffman wrote:
> Interesting. What did the KenTon SCSI and SuperIDE drivers don’t differently? I don’t recall ever letting the frustrating keyboard loss that I get on SDC?

Are you sure you're not using the standard floppy driver? That will 
definitely lead to keyboard loss and all the HALT behaviour.

Also, I'd wager the SCSI and IDE drivers are working with fully decoded 
I/O addressing which doesn't change when the MPI slot is changed. Thus, 
they can run with interrupts enabled without having their I/O space get 
remapped. Since the SDC emulates a real floppy controller, it decodes 
off SCS which does get remapped by MPI slot. (Theoretically, you could 
have multiple SDCs on a single machine that way. Or a floppy controller 
and and SDC.) It may just be disabling interrupts on the way in and 
leaving them off until the I/O is finished. Theoretically, it should be 
able to re-enable interrupts while it's waiting for the SDC to respond 
to a read or write request, or to finish an operation but that would 
require careful coding to allow for interrupts to be enabled 
periodically during the waiting period while still making sure the slot 
didn't change out from under it.