CPU
Cycle-accurate 65C02
Per-instruction cycle counting, decimal mode and page-crossing penalties, at a faithful 1.023 MHz.
A cycle-accurate Apple IIe Enhanced, with its 65C02, 128 KB and 1.023 MHz clock, compiled from C++ to WebAssembly and drawn in WebGL. It sounds as it should. It takes the same expansion cards the real one did, and the dot-matrix printers on the end of them print.
CPU
Cycle-accurate 65C02
Per-instruction cycle counting, decimal mode and page-crossing penalties, at a faithful 1.023 MHz.
Video
Six video modes
Text 40/80, LoRes, HiRes, Double LoRes & HiRes, with NTSC artifact colors and per-scanline rendering.
Audio
Mockingboard sound
Dual AY-3-8910 chips in stereo, plus the built-in speaker with anti-aliased samples.
Storage
Disk II & SmartPort
GCR encoding with write support for DSK, DO, PO, NIB, WOZ; hard drives via HDV and 2MG.
Display
CRT shader effects
Scanlines, curvature, phosphor glow, vignette and NTSC fringing, or plain green, amber or white monochrome.
Persistence
Save states
Autosave every five seconds, five manual slots, full machine serialization.
Seven slots. Cards can be swapped while the machine is running.
Two 5.25″ floppy drives with stepper-motor emulation and GCR encode/decode.
Two AY-3-8910 sound chips and two VIA 6522 timers, giving stereo across six tone channels and two noise channels.
ProDOS-compatible real-time clock and calendar services.
A full Z80 co-processor at 2.041 MHz with hardware address translation, which is how CP/M runs on an Apple II.
ACIA 6551 serial with WebSocket-to-TCP proxy and Hayes modem emulation. Also drives the ImageWriter printers.
Hard drive controller for two block devices, taking HDV, PO and 2MG images.
Centronics printer interface running the original 341-0005 firmware. It drives the Epson FX-80 and the Apple DMP.
Connect a printer just like the real hardware, send output with PR#1, and watch your documents build up dot by dot on fanfold paper, in the order the carriage would travel, with the buzz of a nine-pin head at the real speed. Standard fanfold sizes or paper you drag to size, colour ribbons, a print history, and export to PNG, PDF or ZIP.
Colour, near letter quality, MouseText
Black and white, correspondence quality
ESC/P, Roman and Italic
Parallel, bit-image graphics
“The whole dot-matrix subsystem, four printer models, the mechanical head and its sound, colour ribbon rendering, paper handling, history and export, was designed and built by Shawn Bullock.”
On the printers
Breakpoints, watchpoints, step-over/out, conditional expressions, and beam breakpoints for position-based debugging.
Hex/ASCII across the full 128 KB with a live read/write heat map.
Merlin-syntax 65C02 assembler; recursive-descent disassembly with flow analysis and symbols.
Applesoft tokenizer and variable inspector; DOS 3.3 / ProDOS browsing with syntax highlighting.
Real-time view of every IIe soft switch, stack viewer, zero-page watch, instruction trace.
Print the current //e screen straight to paper as a bit-image graphics dump, exactly as the ROM would.
Core
C++ compiled to WebAssembly with Emscripten and full link-time optimisation. CPU, MMU, video, audio and every card run at native speed.
Timing
The master clock is driven by Web Audio at 48 kHz, so timing holds in a background tab and sound never drifts from picture.
Threading
The core runs in a Web Worker behind a Proxy wrapper, so the interface never blocks.
Rendering
Per-scanline WebGL catches mid-frame mode changes, through a configurable CRT shader pipeline.
An MCP server and the AG-UI event protocol let a language model drive the emulator: several named tabs, broadcast or targeted commands, and a sandbox mode.
Nothing to install. It opens in a new tab.
RetroTech71, Mike Daley, 2026. Back to the front page.