6502Observations

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Notes here on bugs and undocumented behaviour.
Notes here on bugs and undocumented behaviour.
* [[6502_BRK_and_B_bit|BRK, the B bit]], and other interrupts
* [[6502_BRK_and_B_bit|BRK, the B bit]], and other interrupts
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* [[6502_Taken_Branch_Delays_Interrupts Branches and interrupts]] whereby a taken branch delays interrupt handling
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* [[6502_Taken_Branch_Delays_Interrupts|Branches and interrupts]] whereby a taken branch delays interrupt handling
* [[6502_Unsupported_Opcodes|Unsupported or undocumented opcodes]] such as SAX
* [[6502_Unsupported_Opcodes|Unsupported or undocumented opcodes]] such as SAX
* [[6502_ROR_bug|The ROR bug]] which is found only in rare early devices
* [[6502_ROR_bug|The ROR bug]] which is found only in rare early devices

Revision as of 11:42, 10 January 2011

We've found some interesting things on the 6502, from the layout level, up through circuit level to the programmer visible level.

Programmer Visible

Notes here on bugs and undocumented behaviour.

Circuit and Logic

Notes here on timing fixes and non-digital circuit techniques, and departures from NMOS design style orthodoxy.

Layout

Notes here on the traces of bug fixes, and remnants of the original 6501 layout.

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