https://github.com/biged/ioccc-6502

6502 and PET emulator from Stephen Sykes' IOCCC submission
https://github.com/biged/ioccc-6502

Last synced: about 2 months ago
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6502 and PET emulator from Stephen Sykes' IOCCC submission

• Host: GitHub
• URL: https://github.com/biged/ioccc-6502
• Owner: BigEd
• License: cc0-1.0
• Created: 2014-04-16T16:42:56.000Z (almost 11 years ago)
• Default Branch: master
• Last Pushed: 2024-04-27T19:20:43.000Z (9 months ago)
• Last Synced: 2024-10-15T20:23:48.440Z (3 months ago)
• Language: C
• Size: 539 KB
• Stars: 4
• Watchers: 3
• Forks: 2
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
ioccc-6502

==========

6502 and PET emulator from Stephen Sykes' IOCCC submission - see [the official site](http://www.ioccc.org/2005/sykes/) and [Stephen's blog entry](http://www.stephensykes.com/blog_perm.html?112)

The purpose here is to host a bug-fixed version of the emulator, and some efforts at deobfuscation.  See the [hint.text](hint.text) file for details of how to run it. (To run as a PET you will need a ROM image - instructions in the hint file.)

The original submission doesn't successfully run the in-ROM machine monitor, which alerted me to the possibility of bugs.  Other than the absence of decimal mode (which is a relatively common omission and a relatively harmless one) I found these:

* BRK should be a 2-byte opcode

* Bit 4 of the pushed status byte (P) must be zero when pushed by IRQ and otherwise one.

To find the bugs I ran [Klaus Dormann's test suite](https://github.com/Klaus2m5/6502_65C02_functional_tests). The emulator formerly failed and now passes (up to decimal mode.)

Here's a screenshot of the code:

![PET (shaped) emulator](screenshots/PET-source-code.png "Source code shaped like a PET")

See also the post on gplus by mos6502 [here](https://plus.google.com/108984290462000253857/posts/FHjRVUPxQQU).

The rules at the time for submissions to the International Obfuscated C Code Contest put winning entries into the public domain - so I've applied a CC0 license.