Distribution_MiSTer/docs/Oric

Oric / Oric Atmos for MiSTer

This repository contains an Oric-1, Oric Atmos, and Pravetz 8D FPGA core for the MiSTer platform. The current development focus is making the core practical for day-to-day software use: TAP loading, snapshot restore, ROM selection, Microdisc support, and MiSTer launcher files. The latest additions:

• Pravetz 8D DOS 8D support for 5.25 floppy disks, compatible with the hardware for the Bulgarian clone
• Fixed F11/F10 Reset/NMI buttons

The core descends from the earlier MiST / SiDi Oric FPGA work. The original project notes and credits are preserved below, but this README now reflects the current MiSTer tree.

Current Status

Implemented and actively maintained:

• Oric-1 and Oric Atmos operation with full 64 KiB RAM.
• Pravetz 8D ROM option with proper keymapping
• ULA video, 6502 CPU, VIA 6522, AY-3-8912 sound and keyboard matrix handling.
• Microdisc support with EDSK / CPC DSK images.
• TAP loading through the MiSTer file loader.
• Original cassette-audio loading path via VIA cassette input behavior.
• Smart CLOAD menu with three modes:
  • Fast: default mode, keeps the ROM tape flow in charge while feeding TAP bytes directly and aligning ROM sync to TAP leader bytes.
  • Ultra: segment-copy loader for simple CLOAD flows.
  • Off: original cassette/VIA behavior.
• Autoload TAP setting for resetting into CLOAD"" after a TAP is selected.
• Oricutron-compatible .sna snapshot loading for RAM, CPU, AY and VIA state.
• MGL launcher samples for TAP files and snapshots.
• Pravezt 8D DOS support

Snapshot SAVE is not implemented.

Repository Layout

• rtl/ - VHDL/Verilog implementation modules.
• docs/ - technical notes and implementation references.
• tools/ - build, TAP inspection, TAP merge/split, and SNA inspection tools.
• games/Oric/tap/ - TAP files using the target MiSTer games layout.
• games/Oric/snapshots/ - Oricutron .sna files using the target games layout.
• _Games/_Oric/_tap/ - sample MGL launchers for TAP files.
• _Games/_Oric/_snapshots/ - sample MGL launchers for snapshots.
• dsk/ - disk images in the supported EDSK format.
• releases/ - checked-in release .rbf builds.

Start with docs/docs.md for the documentation index and tools/tool.md for the tool summary.

Building

Build the core with:

./tools/oric-build

The build script compiles Oric.qpf. Its deployment behavior is intended for the maintainer's local MiSTer setup, so check docs/build.md before relying on it unchanged.

Useful references:

• docs/build.md - build workflow, clean builds, release naming, and troubleshooting notes.
• tools/tool.md - command summaries and examples.

Loading Software

For TAP files, place software under the MiSTer games path (adjust /media/fat with something else if you use NAS or USB disk/pen):

/media/fat/games/Oric/tap

The matching MGL launchers belong under:

/media/fat/_Games/_Oric/_tap

For snapshots, place .sna files under:

/media/fat/games/Oric/snapshots

The matching snapshot MGL launchers belong under:

/media/fat/_Games/_Oric/_snapshots

The bundled tree mirrors those target paths in games/Oric/ and _Games/_Oric/.

Documentation Highlights

• docs/tape_loading.md - TAP modes, Autoload TAP, Smart CLOAD, Fast vs Ultra, and cassette fallback.
• docs/sna_support.md - Oricutron snapshot support and restore details.
• docs/oric_memory_map.md - Oric memory map, I/O windows, vectors, and hardware overview.
• docs/oric_to_core_comm.md - communication between the 6502 and FPGA core.
• docs/live_rom_patching.md - ROM read-side patching used by Smart CLOAD.
• docs/Oric Rom.md - searchable Atmos ROM disassembly.

Oricutron source were used to gain insights on the snapshot format

Disk Images

Despite the .dsk extension, disk images must use the de facto EDSK / CPC DSK format. To convert Oric disk images, use HxCFloppyEmulator and export as CPC DSK file, keeping the .dsk extension for MiSTer use.

If a disk is bootable, select it from the OSD, exit the OSD, then reset the core. If it is not bootable, try DIR and then !NAME_OF_FILE_TO_RUN.

Original Project Credits

This core builds on earlier Oric FPGA preservation work for MiST and SiDi.

• Ron Rodritty: team coordination and QA testing.
• Fernando Mosquera: FPGA.
• Subcritical: Verilog and VHDL.
• ManuFerHi: hardware consulting.
• Chema Enguita: Oric software.
• SiliceBit: Oric hardware.
• ZXMarce: hardware support.
• Ramon Martinez: Oric hardware, software, and FPGA coding.
• Slingshot: SDRAM work and advice.

Thanks also to Sorgelig, Gehstock, DesUBIKado, RetroWiki, and friends.