mirror of
https://github.com/mist64/perfect6502.git
synced 2024-06-08 12:29:28 +00:00
3e60b6dd44
* also changed "clang" to "cc" * enabled optimizations for 64 bit (it's 10 years later!) * updated README to reflect CPU speed in 2020 (5x faster than 2014!) * added benchmarking instructions to README
43 lines
1.6 KiB
Markdown
43 lines
1.6 KiB
Markdown
# perfect6502
|
||
|
||
*perfect6502* is a MOS 6502 CPU emulator that performs a simulation of the original NMOS 6502 netlist that was extracted by the [visual6502.org](http://www.visual6502.org/) project.
|
||
|
||
Consequently, *perfect6502* is
|
||
* *perfect*: It is not a reimplementation of the 6502, but a simulation of the original transistors. Its complete behavior, its internal state and its outputs are half-cycle exact.
|
||
* *slow*: Even though *perfect6502* is highly optimized C code, achieves only 1/30 of the speed of a 1 MHz 6502 on a high-end CPU of 2020.
|
||
|
||
*perfect6502* is useful for
|
||
* understanding and reverse engineering the 6502
|
||
* debugging 6502 emulators by running them side by side with *perfect6502*
|
||
|
||
## Usage
|
||
|
||
As a demonstration and as a performance/regression test, *perfect6502* is hooked up to [Commodore BASIC](http://en.wikipedia.org/wiki/Commodore_BASIC) (cbmbasic).
|
||
|
||
You can compile the project with
|
||
|
||
$ make
|
||
|
||
and run it with
|
||
|
||
$ cbmbasic/cbmbasic
|
||
|
||
You should get the following output:
|
||
|
||
**** COMMODORE 64 BASIC V2 ****
|
||
|
||
64K RAM SYSTEM 38911 BASIC BYTES FREE
|
||
|
||
READY.
|
||
|
||
## Benchmarking
|
||
|
||
You can use the UNIX `time` tool to measure the performance of the emulator. Run `time cbmbasic/cbmbasic` and press Ctrl+C once it has reached `READY.` – the "user" time is the effective time that was required to reach character input. On a 1 MHz 6502, this takes 0.05 sec.
|
||
|
||
# Credits
|
||
|
||
*perfect6502* is is written by [Michael Steil](http://www.pagetable.com/) and derived from the JavaScript [visual6502](https://github.com/trebonian/visual6502) implementation by Greg James, Brian Silverman and Barry Silverman.
|
||
|
||
# Contributing
|
||
|
||
Further performance optimizations are gladly accepted. |