X64sc Requirement Coverage

X64SC Requirement Coverage

Document Information

Field	Value
Backfill Plan	Backfill Imported Requirements To x64sc Parity
Target Emulator	x64sc
Last Updated	2026-05-21
Owning TODO	BACKFILL-COVERAGE-001

Classification Rules

Each imported FR is classified for the x64sc backfill with one of these values:

Classification	Meaning
x64sc Required	Must be implemented and validated for x64sc parity.
Shared Infrastructure	Needed by x64sc indirectly, usually through drive, resource, build, or host infrastructure.
Out Of x64sc Scope	Imported behavior belongs to a non-x64sc machine family and is not part of this backfill.
Deferred After x64sc	Useful behavior that can wait until after the x64sc parity gate.

Coverage Matrix

Requirement Area	FR IDs	Classification	Owning TODO	Notes
CPU 6510 execution	FR-CPU-001 to FR-CPU-004	x64sc Required	BACKFILL-CORE-001	Includes undocumented NMOS behavior, exact cycle timing, interrupts, and the 6510 I/O port.
C128 8502 mode	FR-CPU-005	Out Of x64sc Scope	none	C128 is imported but outside the x64sc target.
Memory and PLA banking	FR-MEM-001 to FR-MEM-006	x64sc Required	BACKFILL-CORE-001	Includes Ultimax memory mode, VIC bank switching, color RAM, zero page, stack behavior, and definable system-core PLA/address-decoder policy assembled by ArchitectureBuilder.
VIC-II rendering and timing	FR-VIC-001 to FR-VIC-010	x64sc Required	BACKFILL-VIDEO-001	Must cover PAL, NTSC, old NTSC, PAL-N, 6567, 6569, 6572, 8562, and 8565 timing. Border behavior includes closed-border sprite masking and opened-border sprite visibility from FR-VIC-007; sprite DMA timing must use model-specific VICE tables from FR-VIC-010.
SID audio	FR-SID-001 to FR-SID-014	x64sc Required	BACKFILL-SID-001	Includes 6581, 8580, filter differences, digi playback, multi-SID configuration where x64sc exposes it, backend audio wiring, and VICE-compatible signed-output pacing.
CIA I/O	FR-CIA-001 to FR-CIA-007	x64sc Required	BACKFILL-CORE-001	Includes timers, TOD, keyboard matrix scanning, joystick reads, shift register, IRQ, and NMI behavior.
VIA chip core	FR-VIA-001 to FR-VIA-003	Shared Infrastructure	BACKFILL-MEDIA-001	Required for drive-side behavior, not the C64 motherboard.
VIC-20 VIA integration	FR-VIA-004	Out Of x64sc Scope	none	Belongs to xvic, not x64sc.
Disk drive VIA integration	FR-VIA-005	Shared Infrastructure	BACKFILL-MEDIA-001	Required by 1541/IEC parity for x64sc.
Disk and IEC	FR-DRV-001 to FR-DRV-006	x64sc Required	BACKFILL-MEDIA-001	Covers 1541 baseline plus x64sc-supported drive attachment and fast loader behavior.
Tape and datasette	FR-TAP-001 to FR-TAP-005	x64sc Required	BACKFILL-MEDIA-001	SX-64 and C64GS profile quirks must be handled by model-specific resource/peripheral policy.
Cartridge	FR-CRT-001 to FR-CRT-005	x64sc Required	BACKFILL-MEDIA-001	Includes Ultimax/MAX and C64GS boot requirements.
Input devices and VKM	FR-INP-001 to FR-INP-006	x64sc Required	BACKFILL-INPUT-001	Keyboard matrix, control ports, paddles, mouse, lightpen, and VICE keymaps are x64sc parity inputs.
Monitor	FR-MON-001 to FR-MON-006	x64sc Required	BACKFILL-HOSTUI-001	Monitor commands must route through the host control surface.
Snapshot and replay	FR-SNP-001 to FR-SNP-004	x64sc Required	BACKFILL-MEDIA-001	Final validation relies on deterministic state capture and comparison.
Media capture	FR-MED-001 to FR-MED-005	x64sc Required	BACKFILL-MEDIA-001	Host/UI capture entrypoints stay behind the control boundary.
Host and gRPC boundary	FR-HOST-001 to FR-HOST-006	x64sc Required	BACKFILL-HOSTUI-001	gRPC remains the control, configuration, media, input, and monitor boundary.
Avalonia control UI	FR-UI-001 to FR-UI-004	x64sc Required	BACKFILL-HOSTUI-001	The renderer may stay direct in-process; controls route through host abstractions.
Configuration and resources	FR-CFG-001 to FR-CFG-008	x64sc Required	BACKFILL-CORE-001, BACKFILL-MEDIA-001, BACKFILL-HOSTUI-001	Required for model selection, ROM selection, palettes, autostart, hotkeys, peripherals, debug behavior, and limiter settings.
Existing C64-family profiles	FR-PRF-001 to FR-PRF-003	x64sc Required	BACKFILL-MODEL-001	Existing imported profile FRs cover C64, C64C, and SX-64.
Non-x64sc machine profiles	FR-PRF-004 to FR-PRF-008	Out Of x64sc Scope	none	C128, VIC-20, PET, Plus/4, and C16 are imported but deferred until after x64sc.

Additional x64sc Model Coverage

The imported machine profile FRs do not yet assign standalone IDs for old PAL/NTSC, PAL-N/Drean, PET64, Ultimax/MAX, C64GS, or Japanese C64. They are required by the x64sc parity target and are covered by BACKFILL-MODEL-001 plus X64SC-Model-Matrix.md until a later requirements cleanup splits them into canonical FR IDs.

Test Mapping Baseline

Coverage Area	Test Requirement
CPU	TEST-CPU-001
Memory and banking	TEST-MEM-001
VIC-II	TEST-VIC-001
SID	TEST-SID-001, TEST-SID-002
CIA and keyboard matrix	TEST-CIA-001
VIA and drive integration	TEST-VIA-001, TEST-DRV-001
Tape	TEST-TAP-001
Cartridge	TEST-CRT-001
Input and VKM	TEST-INPUT-001
Monitor	TEST-MON-001
Snapshot/replay	TEST-SNP-001
Media capture	TEST-MED-001
Machine profiles	TEST-PRF-001
gRPC and host	TEST-GRPC-001, TEST-HOST-001
UI shell	TEST-UI-001
Configuration/resources	TEST-CFG-001
Final x64sc parity gate	TEST-X64SC-LOCKSTEP-001

Current Evidence

• Baseline solution validation before this slice: dotnet test .\ViceSharp.slnx --nologo passed with 93 tests.
• Profile-focused validation for this slice: dotnet test .\ViceSharp.slnx --nologo --filter C64MachineProfileTests passed with 47 tests.
• Core-definition scaffold validation: x64sc profiles now expose ISystemCoreDefinition policy for board, PLA/address decoder, bus, keyboard matrix, and cartridge boot behavior; dotnet test .\ViceSharp.slnx --nologo --filter "C64MachineProfileTests|HostInputServiceTests" passed with 54 tests.
• Architecture-builder boundary validation: ArchitectureBuilder now registers the profile-selected ISystemCore beside CPU/VIC/SID/CIA/PLA chips, preserving the builder as the glue between system-core policy and chip instances; dotnet test .\ViceSharp.slnx --nologo passed with 154 tests.
• Native x64sc selector validation: the shim now creates native machines with profile-specific x64sc model selectors, applies deterministic cartridge state for Ultimax/MAX and C64GS smoke coverage, exposes native physical RAM and interrupt reads, and validates CPU register/cycle parity plus selected physical RAM windows for every required x64sc profile.
• CIA core backfill validation: Timer B can count Timer A underflows instead of Phi2 ticks, TOD writes target clock or alarm according to CRB bit 7, and TOD carry uses BCD-style rollover; dotnet test tests\ViceSharp.TestHarness\ViceSharp.TestHarness.csproj --nologo --filter "FullyQualifiedName~CiaTimerInterruptTests" passed with 6 tests.
• VICE ROM-resource validation: every x64sc profile now maps to the exact VICE c64model.c ROM resources (basic-901226-01.bin, profile-selected KERNAL, profile-selected chargen, and kernal-none.bin for MAX/Ultimax), and builder tests verify the selected bytes are mapped into the machine; dotnet test tests\ViceSharp.TestHarness\ViceSharp.TestHarness.csproj --nologo --filter "FullyQualifiedName~C64MachineProfileTests" passed with 82 tests.
• x64sc raster/chip checkpoint validation: X64ScVariantLockstepTests now compares native and managed CPU/cycle state, selected physical RAM windows, VIC-II raster line/cycle/badline checkpoints, stable CIA register checkpoints, SID register checkpoints, and IRQ/NMI assertion state after one profile-specific scanline for every required x64sc profile. C64GS is validated with a deterministic 512K GS cartridge and profile-selected GS KERNAL resource; dotnet test tests\ViceSharp.TestHarness\ViceSharp.TestHarness.csproj --nologo --filter "FullyQualifiedName~X64ScVariantLockstepTests" passed with 74 tests.
• Latest VIC-II edge validation: TR-VIC-EDGE-002 carries opened side-border state through Mos6569 and VideoRenderer; TR-VIC-EDGE-006 matches VICE/x64sc readback masks for $D019, $D01A, unused $D02F-$D03F, and collision-register write behavior; and TR-VIC-EDGE-005 now covers managed matrix/idle fetch behavior from viciisc/vicii-fetch.c, including $ff prefetch matrix fill, raw CPU-PC RAM color nibbles, standard-text latch consumption, and ECM $39ff idle graphics reads. Focused matrix/idle plus adjacent timing validation passed 18/18, broader VIC/video validation passed 179/179, and tools\check_requirement_traceability.ps1 passed with 163 canonical IDs, 82 referenced canonical IDs, 81 unreferenced canonical IDs, and 53 noncanonical references.
• Current full-solution validation: dotnet test .\ViceSharp.slnx --no-build --nologo was attempted on 2026-05-21 and timed out after five minutes, then leftover test processes were stopped cleanly. Treat the current green evidence as focused, not solution-wide.
• MCP TODO epics now exist for coverage, model profiles, core timing, video, input, media, SID, host/UI, and final lockstep.

Closure Rule

This coverage document is not final parity evidence. The backfill closes only when BACKFILL-LOCKSTEP-001 passes native x64sc lockstep for every required profile without skipped or unsupported variants.