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This PR fixes all discrepancies of sim65 instruction timings, for both the 6502 and the 65C02 processors. The timings as implemented in this PR have been verified against actual hardware (Atari 800 XL for 6502; and WDC 65C02 for 65C02). These timings can also be verified against the 65x02 test suite. However, in this case, a single discrepancy arises; the 65x02 testsuite suggests that the 65C02 opcode 0x5c should take 4 clocks. However, tests on a hardware 65C02 have conclusively shown that this instruction takes 8 clock cycles. The 8 clock cycles duration for the 65C02 0xfc opcode is also confirmed by other sources, e.g. Section 9 of http://www.6502.org/tutorials/65c02opcodes.html. This test makes sim65 correct both in terms of functionality (all opcodes now do what they do on hardware) and in terms of timing (all instructions take as long as they would on real hardware). The one discrepancy that remains, is that on a real 6502/65C02, some instructions issue R or W cycles on the bus while the instruction processing is being done. Those spurious bus cycles are not replicated in sim65. Sim65 is thus an instruction-level simulator, rather than a bus-cycle level simulator. In other words, while the clock cycle counts for each instruction are now correct, not all clock cycles are individually simulated.
The cc65 cross-compiler suite
cc65 is a complete cross-development package for 65(C)02 systems, including a powerful macro assembler, a C compiler, linker, archiver, simulator and several other tools. cc65 has C and runtime library support for many of the old 6502 machines. For details look at the cc65 web site:
| Company / People | Machine / Environment |
|---|---|
| Apple | Apple II |
| Apple IIe enhanced | |
| Atari | Atari 400/800 |
| Atari 2600 | |
| Atari 5200 | |
| Atari 7800 | |
| Atari XL | |
| Lynx | |
| Tangerine | Oric Atmos |
| Eureka | Oric Telestrat |
| Acorn | BBC series |
| Commodore | C128 |
| C16 | |
| C64 | |
| CBM 510/610 | |
| PET | |
| Plus/4 | |
| VIC-20 | |
| VTech | CreatiVision |
| Commander X16 Community | Commander X16 |
| Bit Corporation | Gamate |
| Berkeley Softworks | GEOS (Apple/CBM) |
| LUnix Team | LUnix (C64) |
| Nintendo | Nintendo Entertainment System (NES) |
| Ohio Scientific | OSI C1P |
| MOS Technology, Inc. | KIM-1 |
| NEC | PC Engine (PCE) |
| Dr. Jozo Dujmović | Picocomputer (RP6502) |
| Watara | Watura/QuickShot Supervision |
| Synertek | SYM-1 |
A generic configuration to adapt cc65 to new targets is also around.
People
cc65 is originally based on the "Small C" compiler by Ron Cain and enhanced by James E. Hendrix.
Project founders
- John R. Dunning: original implementation of the C compiler and runtime library, Atari hosted.
- Ullrich von Bassewitz:
- moved Dunning's code to modern systems,
- rewrote most parts of the compiler,
- rewrote all of the runtime library.
Core team members
- Christian Groessler: Atari, Atari5200, and CreatiVision library Maintainer
- dqh: GHA help
- Greg King: all around hackery
- groepaz: CBM library, Project Maintainer
- Oliver Schmidt: Apple II library Maintainer
External contributors
- acqn: various compiler fixes
- jedeoric: Telestrat target
- jmr: compiler fixes
- karrika: Atari 7800 target
- Stephan Mühlstrasser: osic1p target
- Wayne Parham: Sym-1 target
- Dave Plummer: KIM-1 target
- rumbledethumps: Picocomputer target
(The above list is incomplete, if you feel left out - please speak up or add yourself in a PR)
For a complete list look at the full team list or the list of all contributors.
Contact
For general discussion, questions, etc subscribe to the mailing list or use the github discussions.
Some of us may also be around on IRC #cc65 on libera.chat.
Documentation
- The main Documentation for users and developers.
- Info on Contributing to the CC65 project. Please read this before working on something you want to contribute, and before reporting bugs.
- The Wiki contains some extra info that does not fit into the regular documentation.
Downloads
