Commodore 64 Emulator v0.8.1.0-alpha is released. A Commodore 64 emulator written in modern C++, built with SDL2 and designed around two priorities:Accuracy-first emulation (with a strong focus on real hardware behavior over “good enough” hacks); Debuggability (integrated monitor, break/watchpoints, and visibility into what the machine is doing). This project is actively under development; expect rough edges and incomplete features.

Commodore 64 Emulator Changelog:
This alpha release focuses on C64 emulator accuracy, reset behavior, cartridge groundwork, IEC drive synchronization, disk activity handling, and ML monitor/debugging improvements.
Highlights
Improved C64 cold/warm reset handling
Fixed IEC drive detection issues after cold reset and disk changes
Improved 1541 and 1571 reset synchronization
1581 drive now loads .d81 images correctly and blank .d81 disk creation works
Continued VIC-II timing work toward more cycle/pixel accuracy
Continued cartridge infrastructure cleanup
Added early groundwork for IDE64 cartridge support
Improved ML monitor command handling and help routing
C64 Core
Reset / Startup
Improved reset controller behavior for cold and warm resets.
Improved system state restoration during reset.
Fixed an issue where changing an inserted disk after cold reset could cause the first disk access to fail with DEVICE NOT PRESENT.
Improved synchronization between the C64 IEC bus state and attached drives during reset.
Cleaned up reset flow so devices are restored into a more predictable state.
VIC-II / Video
Continued groundwork for moving the VIC-II toward more cycle-accurate and pixel-based behavior.
Improved internal timing structure around raster/cycle progression.
Continued work around:
raster timing
badline behavior
DMA timing
register latching
sprite rendering behavior
display enable timing
Added more structure for future VIC-II accuracy improvements.
IEC / Disk Drive Handling
General IEC
Improved IEC bus/device resynchronization after reset.
Fixed first-access drive detection problems after disk changes.
Improved reset-time IEC line propagation into drive-side VIA/CIA state.
Reduced cases where drives could briefly appear unavailable immediately after reset.
1541
Improved reset synchronization with the IEC bus.
Fixed an issue where the 1541 could report DEVICE NOT PRESENT on the first access after changing disks following a cold reset.
Improved VIA IEC input line restoration during reset.
1571
Applied similar reset synchronization improvements as the 1541.
Improved IEC state restoration after reset.
Fixed first-access detection issues after changing disks.
Continued work toward more accurate 1571 ROM-driven behavior.
1581
Improved disk activity LED behavior.
Investigated and refined cases where the LED turned off too quickly during loads.
Improved activity tracking so the LED is not dependent only on track/sector changes.
Better handles directory loads and repeated reads where the track/sector may not visibly change.
Continued tuning toward more realistic 1581 activity timing.
Cartridge Support
Continued cleanup of cartridge infrastructure and cartridge type handling.
Added early groundwork for IDE64 cartridge support.
Reviewed remaining IDE64 implementation requirements before modeling it as a full device.
Continued work on mapper/system integration paths.
Improved cartridge-related organization for future expansion.
ML Monitor / Debugger
Improved monitor command handling.
Fixed help behavior so command-specific help can be displayed instead of always printing the full command list.
Improved command routing structure for future monitor expansion.
Continued cleanup of monitor command formatting and consistency.
Developer / Debugging Improvements
Improved traceability of reset and device state issues.
Improved ability to diagnose IEC bus state during reset.
Added cleaner paths for monitor-driven debugging.
Continued cleanup of helper formatting and command output.
Improved emulator state visibility during drive and reset testing.
Bug Fixes
Fixed IEC device presence issue after cold reset and disk swap.
Fixed 1541 first-access failure after changing disks.
Fixed 1571 first-access failure after changing disks.
Fixed monitor help routing.
Improved 1581 LED behavior where the activity light shut off too soon during loading.
Reduced reset-state inconsistencies between C64, IEC bus, and attached drives.
Known Issues / Work in Progress
IDE64 support is still early and not yet a complete emulated device.
VIC-II pixel/cycle accuracy work is ongoing.
1571 behavior is still being refined, especially around ROM-driven operation.
1581 activity LED timing may still need additional tuning.
Cartridge mapper support continues to be expanded and validated.
ML monitor assembler/disassembler support is still under development.
Summary
v0.8.1.0-alpha is a C64-focused accuracy and infrastructure release. It improves reset behavior, IEC drive synchronization, disk activity handling, cartridge groundwork, and monitor usability while continuing the larger move toward more hardware-accurate emulation.

Download: Commodore 64 Emulator v0.8.1.0-alpha
Source: Here