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#140 Debug Monitor shows inconsistent RAM contents compared to actual memory (SMON verification)

open
nobody
C64
macOS
5 days ago
5 days ago
ClausS
No

I found an inconsistency between the Debug Monitor memory view and the actual C64 memory contents.
When writing a continuous memory block using a monitor tool (SMON), the data is correctly written and can be verified within SMON itself. However, the Debug Monitor shows incorrect or inconsistent data in the same memory range.

Steps to Reproduce

  1. Start Denise
  2. Launch a machine code monitor (e.g. SMON)
  3. Fill a memory range, for example:
    o 2000 4000 cc`
  4. Verify the memory inside SMON:
    • The entire range is correctly filled with $CC
  5. Open the Debug Monitor memory view
  6. Inspect the same memory range ($2000–$3FFF)

Observed Behavior
• The Debug Monitor initially shows correct values ($CC)
• After a certain point (e.g. around $2200), the data becomes inconsistent
• Some regions show unexpected values
• Further ahead, correct $CC values appear again
• The incorrect regions appear in blocks, not randomly

Expected Behavior
• The Debug Monitor should display a continuous block of $CC values across the entire range ($2000–$3FFF), matching the actual RAM contents.

Notes
• The issue only affects the Debug Monitor display
• The actual memory contents are correct (verified via SMON)
• This suggests a problem in the Debug Monitor memory source or address mapping

Environment
• Denise version: 2.7 (nightly)
• Platform: macOS (Apple Silicon)

Discussion

  • PiCiJi

    PiCiJi - 5 days ago

    Good find, thanks.
    Something seems to be wrong with the update. I'll fix it.

     
  • PiCiJi

    PiCiJi - 5 days ago

    should be fixed in latest nightly

     
    • ClausS

      ClausS - 5 days ago

      Thanks for the quick response! I’ll test it as soon as the next nightly build is available.

       
      • ClausS

        ClausS - 5 days ago

        I have tested with latest nightly build, the issue appears to be fixed.
        The memory display is now consistent across full ranges.
        Thanks!

         
        👍
        1

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