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Phosphoric

An emulator of the Oric-1 and the Atmos, Tangerine's 8-bit computers (1983). It is written in C11 and cycle-stepped: a master clock moves the whole machine forward one microsecond at a time. Its 6502 core is exact to the cycle, checked on 2,440,000 cases. It runs on Linux, Windows and macOS, and in the browser.

Start with Phosphoric for beginners See the gallery
  • 100%exact bus sequences for the 6502, on the 2,440,000 cases of the 65x02 oracle
  • 1 cycleper call of the master clock: CPU, peripherals and ULA move together
  • 70 suitesof tests, 1,362 checks, all green
  • 3%of a 20 ms frame budget: the cost of going cycle by cycle
Screen full of colour diagonals: 16 colours on 320 × 224 pixels, rendered by Phosphoric's ULA-NG
The ULA-NG, Phosphoric’s “next generation” ULA, in chunky mode: 320 × 224 pixels in 16 colours. Screenshot taken by the emulator itself, with no display.
The machine Phosphoric emulates, and what surrounds itA MOS 6502 processor at 1 MHz and 64 KB of memory (48 KB of RAM, 16 KB of BASIC ROM) share a bus. On this bus: the VIA 6522 (keyboard, tape, printer, interrupts), the ULA (the picture), the AY-3-8912 PSG (sound, and part of the keyboard) and page 3, where expansion cards plug in. On the right, the host: SDL2 window, browser, or no display. At the bottom, the master clock moves the whole machine one cycle at a time.6502MOS 6502 NMOS · 1 MHz64 KB memory48 KB RAM · 16 KB ROMaddress and data busVIA 6522ports and timerskeyboard (8 × 8 matrix)tape, printerinterruptsULAHCS 10017 · the picture40 × 28 text240 × 200 HIRES8 colours, PALPSGAY-3-8912 · sound3 voices and noise16 envelopesport A: keyboardPage 3$0300-$03FFMicrodisc, Jasmin, LOCIACIA, DTL 2000, MIDIspeech, ULA-NGHostSDL2: picture, sound,keyboard, gamepadWebAssemblyno displayscreenshots, AVI, WAVHTTP API, --controlGDB serverMaster clock: emu_cycle() moves the whole machine one cycle (CPU, then φ2, then ULA)
The emulated machine: a 6502, 64 KB of memory, the VIA, the ULA, the PSG and page 3 for expansion cards. Everything moves to the beat of a single clock.

Where to start

Downloads, source code and the project’s articles are on the main site: tachibana.eu/en/phosphoric.