Comments (2)
Tested writing a modified disk via ADT on the IIgs and reading it back on the NES. Works like a charm.
Updated the code to have a boot jump, haven't tested it yet. Here we goooooo
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Haven't updated in about a week because AiO inc got me chucked off on another sidequest for the last couple of days.
I reconfigured the hardware slightly so that now we have the following mapping modes:
Mode 0
0x8000-0xBFFF --> SRAM 0x0000-0x3FFF
0xC000-0xCFFF --> Slot select area
0xD000-0xDFFF --> Write here to change mode
0xE000-0xFFFF --> ROM 0x6000-0x7FFF
Cart mirroring: H
Mode 1
0x8000-0xFFFF --> SRAM 0x0000-0x7FFF
Cart mirroring: H
Mode 2
0x8000-0xBFFF --> SRAM 0x4000-0x7FFF
0xC000-0xCFFF --> Slot select area
0xD000-0xDFFF --> Write here to change mode
0xE000-0xFFFF --> ROM 0x6000-0x7FFF
Cart mirroring: H
Mode 3
0x8000-0xFFFF --> SRAM 0x0000-0x7FFF
Cart mirroring: V
With this hardware configuration I was then able to write a script that accepts an iNES-format ROM and, if it's compatible (no more than 32K PRG and 8K CHR), convert it into a self-booting .DSK image that copies the low 16K of PRG from the disk to the first SRAM bank, swaps the SRAM bank, copies the next 16K of PRG to it, then copies the 8K of CHR to the CHR-RAM and finally switches the cart mode to 1 or 3 depending on the required mirroring and jumps indirect to the reset vector in PRG RAM.
So, yeah. It can boot basic NES games off floppy now.
I guess that means I can close out this issue and open one up for implementing NOS (NES [disk] Operating System).
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Related Issues (20)
- [NES II] Read a sector HOT 4
- [NES II] Read and display the catalog from an Apple DOS 3.3-compatible disk HOT 2
- [NES II] Load and execute an Apple DOS 3.3 bin format executable HOT 8
- [NES II] Run NES game image from DOS filesystem HOT 4
- [NES II] Fix bottom line clearing during screen scroll HOT 1
- [NES II] Use check-for-data-changing floppy motor wait hack HOT 1
- [NES II] Add disk read timeout to bios HOT 2
- [NES II] Write a sector to a floppy
- [NES II] Implement a 'not an Apple II disk' warning in NOS boot code
- [NES II] Implement a 'not an Apple II program' warning in NES game loaders
- [NES II] Implement BIOS update module system HOT 3
- [NES II] Update SHELL to load any BIOS update modules found on the disk at startup HOT 1
- [NES II] Implement file create call
- [NES II] Implement file delete call
- [NES II] Implement file write call
- [NES II] Get BASIC running
- [NES II] Support execution of HELLO WORLD in BASIC
- [NES II] Support loading and running file from disk in BASIC
- [NES II] Support saving current file to disk in BASIC
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