The SCSI-NuBus Test Card also has some RAM on board for the testing of DeclROM images to boot the Mac OS from an attached SCSI Drive.
"In addition, the card provides a small RAM, which is accessible in super slot space for the testing of 32-bit address mode switching.
The ROM is really a RAM that can write to in the assigned ROM address space. The RAM chip may be replaced with a real ROM when desired."
This leads me to believe that the IDE HDD might be addressable as Virtual Memory in the super slot address space. If this is the case, could some kind of HDD controller IC be addressed as if it were one big block of VM or a BIG@$$ RAM Disk to get around the programming needed for treating it as Hard Disk? Regular toolbox routines ought to cover the VM angle and much of the programming would then be toolbox calls . . . or not.
All the source code and equations for the three PALs on the SCSI card are included in Appendix E. Chapter 9 offers information and NuBus specific notes about NuBus card drivers to supplement the General Guidelines for writing drivers in the Device Manager information in Inside Macintosh.
Unfortunately, the Firmware Sample in Appendix B and the Driver Example in Appendix C are both for the Video Card Design, not the NuBus SCSI Card. :-/
Like I said, this is waaaayyyyyy over my head! I can make connections that lead to over the top suggestions, but implementing anything in software is NOT my thing . . . maybe a little PCB prototyping would be OK! }
"In addition, the card provides a small RAM, which is accessible in super slot space for the testing of 32-bit address mode switching.
The ROM is really a RAM that can write to in the assigned ROM address space. The RAM chip may be replaced with a real ROM when desired."
This leads me to believe that the IDE HDD might be addressable as Virtual Memory in the super slot address space. If this is the case, could some kind of HDD controller IC be addressed as if it were one big block of VM or a BIG@$$ RAM Disk to get around the programming needed for treating it as Hard Disk? Regular toolbox routines ought to cover the VM angle and much of the programming would then be toolbox calls . . . or not.
All the source code and equations for the three PALs on the SCSI card are included in Appendix E. Chapter 9 offers information and NuBus specific notes about NuBus card drivers to supplement the General Guidelines for writing drivers in the Device Manager information in Inside Macintosh.
Unfortunately, the Firmware Sample in Appendix B and the Driver Example in Appendix C are both for the Video Card Design, not the NuBus SCSI Card. :-/
Like I said, this is waaaayyyyyy over my head! I can make connections that lead to over the top suggestions, but implementing anything in software is NOT my thing . . . maybe a little PCB prototyping would be OK! }