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MEGA65 ROM Change Log

This change log lists user-facing changes to the MEGA65 ROM between numbered versions. See README.md for more information about version numbering and releases.

The latest stable ROM release is ROM 920395, in release package v0.96. It was declared stable on February 25, 2024. ROM 920395 requires the v0.96 core, or the Xemu emulator "stable" version released on February 28, 2024 or later.

The latest ROM beta version

We release beta versions of the ROM that are newer than the latest stable release, to solicit help with testing from the community and to provide early previews of new features. Be aware that beta versions may require a newer core, and may have known issues. Please file bugs as you find them.

The latest ROM beta version is ROM 920408. Changes since release v0.96 (ROM 920395):

  • 920408

    • Fix: DECBIN was also mishandling string lengths, similar to DEC.
    • Fix: KEY macro sizes were not limited correctly, very long macros were corrupting memory.
    • Fix: Text highlight register was not getting initialized correctly, was causing disk error highlight colors to stick (orange text) under specific circumstances.
    • Fix: RMOUSE with non-0 sprite was reporting large X coordinates incorrectly. (Thanks Pimau!)

  • 920407

    • Fix: DEC() was mishandling string lengths, sometimes returning wrong values.
    • Fix: OPEN now clears DS when opening a disk device. This fixes an edge case in Eleven where a failure to load the last-loaded file on start-up would cause subsequent successful loads to report failure.

  • 920406

    • Fix: LOAD KERNAL API in "raw" mode now returns a File Not Found error. One caveat to this fix: when loading a PRG-type file in raw mode, it must be at least two bytes long, even though the bytes are interpreted as data. Technically all PRG-type files must be at least two bytes long, so this is fairly complete, but maybe doesn't fully capture the use case in edge cases. (IMO, a file type that must allow sizes of 0 or 1 ought to be SEQ files.) I added this limitation to the docs.
    • Fix: CONT now works when the program stopped during a subroutine, either with the STOP command or with Run/Stop.
    • Fix: FOR with byte variable now throws Illegal Quantity Error on an over-large TO, instead of infinite looping.
    • Fix: FOR with byte variable can use TO targets of 0 and 255.

  • 920405

    • Change: Support for the RENUMBER100-style syntax for "crunch" mode has been removed, in favor of RENUMBER C 100. If it is any consolation, RENUMBERC100 also works. 😅 Hopefully this is different enough to prevent accidental activation.
    • Fix: FN X() argument can now be an array element, was previously reporting Syntax Error.
    • Fix: FOR index variable can now be a byte variable (B&). The variable truncates on assignment after STEP is added. Take care that the TO value is in byte range, to prevent an infinite loop.
    • Fix: DLOAD failure during Edit mode now reports ?OK ERROR. Previously it was silent. It's not perfect—DS still isn't set—but it's an improvement.
    • Fix: MOVSPR no longer overshoots the target position.

  • 920404

    • New: PRINT USING %-style patterns now support left zero padding for positive values in float and integer patters: %07.2F %05D Left zero padding is cancelled if the value is negative. Right-of-decimal fields and hexadecimal patterns are always left zero padded, as before.
    • New: RWINDOW(3) returns the screen height in rows, regardless of window size, similar to how RWINDOW(2) returns the screen width in columns.
    • Improvement: RENUMBER "crunch" mode that elides leading whitespace before line numbers now has an explicit flag: RENUMBER C 100 I would like to remove the RENUMBER100-style syntax in a future version because this is a destructive action and too easy to trigger accidentally this way. This ROM version supports both syntaxes for now.
    • Improvement: When in 80x50 mode, ESC+X goes to 80x25, then toggles between 80x25 and 40x25 thereafter. Previously, this did nothing in 80x50 mode. This also applies to the (mostly useless) "SWAPPER" KERNAL call.
    • Fix: Physical floppy drive resets the drive head properly on next directory read after an error, fixing a regression from 920403. This is believed to be the cause of the oddball floppy drive issues with "D64 support" in ROM 920381, even though that specific case was not reproduceable in 920403. Wayne found a reproduceable case this time around, and we determined that the logic that "D64 support" replaced was doing a sector read that the new version wasn't doing. There is now a dummy sector read in this call path to force a reset. It should only affect the internal floppy drive, and only in this way.
    • Fix: DS/DS$ disk error variables are now reset correctly for all DOS commands. DOPEN, MERGE, and CHDIR U12 were not resetting them when called, causing confusion when a previous disk command failed and the newer command succeeded.

  • 920403

    • New: D64 support. This change is identical to the one for ROM 920381, but the oddball problems of ROM 920381 + core 0.95 seem to no longer be present with ROM 920403 and core 0.96. We're excited to open this to wider testing.

  • 920402

    • Fix: Regression in PLAY and SOUND from 920401.

  • 920401

    • Fix: BLOAD loads correctly to Attic RAM addresses.
    • Fix: SETBNK setting persists between LOAD calls, was failing in edge cases.
    • Fix: SETBNK more thoroughly respected by BASIC.
    • Fix: Corrects BLOAD and BVERIFY address reporting in edge cases.

  • 920400

    • Fix: Restore the VECTOR change. RESTOR and Run/Stop+Restore correctly use a conditional test for the FDC to choose the default serial/DOS vectors. User calls to VECTOR require a 56-byte table, and can customize the serial and editor vectors.
    • Fix: BLOAD now uses the new SETBNK implementation for both B-argument calls and 28-bit P-argument addresses, resolving a clash between the previous 28-bit implementation and SETBNK.
    • Fix: BSAVE now uses the B-argument correctly.

  • 920399

    • Temporarily revert VECTOR change. The new table length isn't an issue, it was just implemented incorrectly, interfering with DOS's jump table (not yet public) after Run/Stop + Restore. Until this is fixed, VECTOR will only do the first 32 bytes of the vector table. Callers should continue to expect a 56-byte table.

  • 920398

    • Important change: The KERNAL routine VECTOR was previously only copying the first 32 bytes of the vector table. It now copies all 56 bytes. This is a backwards incompatible change, but we believe existing MEGA65 software is not using this routine. If you believe this change is causing an issue with existing software, please file a bug.
    • New: Four new KERNAL routines provide safe access to KERNAL state:
      • GETIO: Read the current input and output devices
      • GETLFS: Read file, device, secondary address
      • KEYLOCKS: Read/set keyboard locks
      • ADDKEY: Add a character to the soft keyboard input buffer
    • New: KERNAL routine SETBNK has been reimplemented to support 28-bit addresses for file data and filenames. The API is backwards compatible with the original 24-bit SETBNK. This routine has been disabled for multiple ROM versions. It is now the official way to set file data upper address bits.
    • New: KERNAL vector KEYSCAN gives a program an opportunity to intercept reading from the keyboard by GETIN, after a key has been read and before it has been interpreted. This replaces C65 vectors that were originally intended for a similar purpose that had to be removed for the new MEGA65 keyboard scanner.
    • Fix: Some programs, especially those compiled with llvm-mos, were crashing when screen printing scrolled the screen.
    • Fix: Run/Stop-Restore (and IOINIT) were not resetting the CPU speed correctly. It now resets to 40 MHz consistently.
    • Note: As a general rule, direct access to KERNAL memory by a program is not supported (for now, at least). We are working to document all supported KERNAL integration techniques, and support new tasks through KERNAL calls. If your program has a need to access KERNAL state that is not covered by the KERNAL jump table routines, please file a feature request.

  • 920397

    • New: JOY(3) returns the combined status of joysticks in either port, allowing for a program to easily support a single joystick in either port without calling JOY() twice.
    • Fix: SPEED no longer trips VIC-IV "hot registers."
    • Fix / workaround: VSYNC no longer hangs when given a value lower than 6 in NTSC mode. The root cause is a core bug in the vertical raster position register. This change causes VSYNC with a value less than 6 in NTSC mode only to act as if the argument is 6. When the core bug is fixed, this workaround can be removed.
    • Fix: Extend RTC detection to notice broken amp.
    • Fix: Restore GO65.

  • 920396

    • New: Binary literals! Use % for binary literal values such as %1010. New DECBIN("...") function converts a binary string of 0 and 1 characters to a number. STRBIN$(number) converts a number to a string of 0 and 1 characters.
    • New: DIR P displays a directory listing, pausing for a key press after each screenful (page). DIR U12,P for listing files on the SD card is also supported.
    • New: TYPE P "filename" displays a text file, pausing for a key press after each screenful (page).
    • New: BLOAD prints the starting and ending address of the loaded memory region when used in immediate mode (at the READY prompt).
    • New: When RENUMBER encounters an Unresolved Reference Error, it also prints the line where the error occurs. (For various reasons, this is not available via the HELP command, as with runtime errors.)
    • New: RPALETTE() now accepts a screen number of -1 to refer to the primary system palette (palette 0). It also accepts -2, -3, and -4 for the other three system palettes (palettes 1-3). Support for using the other system palettes from BASIC is planned for a future release.
    • New: It is now possible to disable "line pushing" in the screen editor, using the escape sequence ESC R (PRINT CHR$(27)+"R"). Use ESC N to re-enable. This allows the PRINT command to write a character to the right-most column without pushing other lines downward. Note that you must still use ESC M (PRINT CHR$(27)+"M") to disable screen scrolling to PRINT a character in the bottom-right corner without scrolling the screen. (Use ESC L to re-enable scrolling.)
    • New: The BASIC sprite subsystem now recognizes and honors the VIC-IV high resolution sprite registers sprenv400 (high-res vertical, per sprite) and sprh640 (high-res horizontal, system-wide). MOVSPR accepts 10-bit X and Y coordinates, and will correctly truncate coordinates in low-res modes. We will be adding a mode for matching the sprite resolution to the screen resolution in a future release. It will always be supported for a BASIC program to set these registers directly. We will also add support for a hires mouse pointer in a future release (tracking issue).
    • Change: The BASIC ROM has been reorganized to make better use of available space. This introduces a new memory map mode to access a new region of ROM space that was previously unused. The BASIC 65 bitplane graphics subsystem has been relocated to this new region, and future additions may also use it.
    • Change: The boot state of register $0001 has changed to start with the datasette lines turned off. The datasette port will be supported in the upcoming expansion board.
    • Change: The v0.96 release ROM included a boot-time error message for when it used with an older core or Xemu version that didn't support the hardware typing queue, to make it easier for upgraders and testers to notice when this happens. This error message has been removed. We may reinstate this for the next release package where the ROM depends on a new feature of the core.
    • Change: The ROM version string in the ROM data is now null terminated, to support external tools reading a variable-length version string.
    • Change: The repeat delay for Mega+Shift, No Scroll, and Ctrl-S has been slowed down. This repeat delay was inadvertently sped up with the new typing system in release v0.96, causing accidental repeats.
    • Fix / Change: The MOUSE command was intended by Fred Bowen to accept arguments to adjust the location of the "hot spot" on the mouse pointer sprite, as well as set the pointer's initial screen position. These arugments were incorrectly documented and also were not functioning correctly. The features have been fixed, using the original intended argument order: MOUSE ON,port,sprite,hotspot-x,hotspot-y,location-x,location-y
    • Fix / Change: Using MOUSE ON when the mouse is already enabled using a different sprite number will disable the previous sprite. (There is only ever one active mouse pointer.)
    • Fix: INFO and RSPEED() detect the CPU speed correctly in an edge case.
    • Fix: Improved CLR TI to reset the TI timer variable.
    • Fix: Edge case where VAL reads one too many characters for signed values.
    • Fix: Edge case where typing a quote in the last position of an inserted space leaves the screen editor in quote mode.
    • Fix: DOS memory map bug.
    • Fix: Monitor requires an argument for the J command.
    • Fix: Monitor restores the base page B CPU register when resuming from a brk. B register is supported by the jmp_far routine (also available as a KERNAL call).
    • Fix: In v0.96, scroll pausing was interrupting regular typing. This now behaves as before: No Scroll and Ctrl-S do nothing at a blinking cursor.
    • Fix: The R Shift+U shortcut for the RUN command has been restored. In general, we can't support command abbreviations as an API, but we will make a best effort to not clobber commonly used ones. See this wiki page.
    • Fix: Run/Stop-Restore sets sprite 0's color to 1 (white) instead of 0 (black), agreeing with the boot state.
    • Note: Similar to the undocumented MOUSE parameters, we noticed that the VOL command was documented incorrectly. It accepts two arguments: a volume for the right stereo channel SIDs, and a volume for the left stereo channel SIDs (VOL 9,9). The ROM has always implemented it this way. We have elected to change the documentation to match the implementation (with no change to the implementation).

Release 0.96: ROM 920395

Release 0.96 is the current stable release package, dated February 2024. It includes ROM 920395 and core 20240224.00,3c10488. This release will be factory installed on MEGA65s shipped in June 2024.

Important: The release v0.96 ROM requires the v0.96 core, or the Xemu emulator from January 2024 or later.

Changes since release 0.95 (920377):

  • 920395

    • Fix: Run/Stop was not being detected correctly under some circumstances.

  • 920394

    • Change: ROM detects whether it is running on a core or Xemu version that does not support the hardware typing queue, and halts boot with a message. This is a short-term convenience for v0.96 release testers and upgraders that might accidentally run the new ROM with an old core/Xemu version, and will be removed after v0.96 is released to reclaim code space. (This is not a long-term solution for forward compatibility testing; see discussion on this issue in the private repo.)

  • 920393

    • Fix: Previous change broke Run/Stop interrupting a BASIC program, now fixed.

  • 920392

    • Fix: BASIC joystick handling now works correctly with the R5 mainboard.

  • 920391

    • DOS and disk command improvements:
      • Fix: Reset DS/DS$ disk status after initial autoboot.
      • Fix: DOS correctly writes the final byte (C64 and MEGA65 modes).
      • Fix: Report correct error for LOAD with inappropriate device numbers.
      • Fix: Repair DOS command channel bugs interfering with U1 and U2 commands.
      • Fix: Repair disk full detection.
      • Fix: Repair disk commands that start with a slash.
      • Improvements to CHDIR, MKDIR, DISK
      • Improvements to MONITOR @ disk command handling
    • Fix: RMOUSE reports mouse movement more precisely.
    • Fix: DOT was corrupting graphics subsystem internal state that interfered with other commands.
    • Fix: TI timer accurate for NTSC, was previously hard-coded for PAL.
    • Fix: SLEEP edge case caused hanging, noticeable on very long delays.
    • Fix: ioinit flushes the hardware keyboard buffer, fewer spurious key events after state transitions.
    • Fix: Improvements to restoring the CPU speed after disk operations.

  • 920390

    • MONITOR (BSMON) improvements:
      • New: Support for assembling and disassembling Q instructions.
      • New: Support for assembling and disassembling MAP and EOM instructions.
      • New: Load/Save/Verify support upper memory addresses.
      • New: Assemble supports editing previously entered lines.
      • New: Assemble can assemble to upper memory addresses.
      • Fix: M with range < 16 bytes shows 16 bytes.
      • Fix: Register handling in Verify.
    • Fix: BSAVE handles internal address variables correctly.
    • Fix: Disk status special variables DS and DS$ retain their values until next disk operation.
    • Fix: GO64 mode preserves ZP memory $B0-$B3 during disk operations. This fixes a regression introduced in ROM 920379 that was interfering with some C64 software that assumed these addresses were safe to use.
    • Many thanks to Wayne (johnwayner) for contributing most of these improvements!

  • 920389

    • Fix: Keyboard scanner was broken in KEY OFF mode, affected MegaAssembler and Coffeebreak Compiler

  • 920388

    • Fix: Keyboard scanner issues with Ctrl and Function keys
    • Fix: TI$ detecting board revision incorrectly

  • 920387 — REQUIRES THE LATEST DEVELOPMENT CORE, at least 20230922.14-develo-dea350f

    • Change: An overhaul of the keyboard scanner to make typing faster and more accurate. This collaborates with a new core feature to avoid dropped keystrokes.
    • Older ROMs will work with the latest core, using the legacy keyboard scanner. This new ROM requires the latest core. If you run this ROM with an earlier core, typing will not work.

  • 920386

    • Change: Restores original screen code-based cursor rendering. A recent ROM beta release updated cursor rendering to use the reverse character attribute instead of the traditional screen code method. Unfortunately, the original VIC-III character attributes are broken when used in combination, so upper palette characters were rendering the cursor incorrectly. There's a core update to fix character attributes, but for backwards compatibility with the C65 prototype ROM this must be requested by setting a register, and the ROM must leave this turned off by default. It's just easier to go back to the screen code cursor.
    • Fix: Issue with reading from color memory special array C@&(x,y)
    • Fix: MID$() could not assign to last character in string
    • Fix: Incorrect TOD50 setting in NTSC mode

  • 920385

    • Change: Implements the MEGA65 cartridge protocol proposal. This should be considered experimental for now just in case the proposal needs to be revised. The full implementation of auto-boot MEGA65 cartridges requires a newer core.
    • Change: Run/Stop-Restore resets the font to the PETSCII default (font "C"), to make text readable when resetting from programs that replace the font with graphics characters
    • Fix: Adding a string and a number is a Type Mismatch Error
    • Fix: RENUMBER supports COLLISION statements
    • Fix: RENUMBER fixes for whitespace handling around THEN and ELSE
    • Fix: (Requires new core) 80x50 mode no longer switches to the wrong screen memory when CPU speed changes. This manifested as half a screen of garbage and instability after DOS operations and the ringing of the bell (Ctrl-G) while 80x50 mode was active.
    • Fix: Repaired instability caused by calling PLAY without arguments within a program
    • Fix: Monitor's Memory and Disassemble commands support full 32-bit ranges consistently

  • 920384

    • Change: The MEGA65 boot state does not bank in the C64 ROM via the $0001 register by default. The boot state configuration of $0001 is now %101 instead of %111. GO64 re-banks the C64 ROM explicitly instead of relying on the boot state.
    • Change: GO64 mode displays a proprietary banner to differentiate between GO64 mode and the C64 core, and to reinforce expectations around software compatibility and availability of MEGA65 features.
    • Fix: PEN throws an error (and does not hang) if no graphics screen is active
    • Fix: SAVEIFF uses correct IFF-ILBM header values to be compatible with modern image tools
    • Fix: CHAR correctly supports all PETSCII printable characters
    • Fix: RENUMBER supports a line number range without an end (RENUMBER 1000,10,2500-)
    • Fix: FOR accepts an initializer expression containing an array element (FOR X=AR(0) TO 20)
    • Some internal BASIC routines have been relocated to make more room for bug fixes above a jump table.
    • An unused region of the ROM space is now filled with $FF instead of a copy of other ROM code, to clarify intent and to avoid an accidental dependency on the copy.

  • 920383

    • Repair for RMOUSE bug introduced in 920382
    • Rollback of "D64 disk image support" introduced in 920381 that was causing floppy drive read errors in rare cases

  • 920382

    • BASIC 80x50 mode: pressing ESC then 5 (or printing CHR$(27) + "5") switches the BASIC text display to 80x50, complementing 80x25 (ESC+8) and 40x25 (ESC+4) text modes

  • 920381

    • D64 disk image support
    • Initialize BASIC sprites: MOUSE ON immediately shows an arrow mouse cursor, without having to install a sprite first; sprites 1-7 are a simple pattern

  • 920380

    • Run Stop + Restore during an ML routine breaks to the monitor with accurate registers
    • SET DISK <old> TO <new> swaps unit numbers of disk drives
    • Code clean-up for kernel routines

  • 920379

    • Refactor CBDOS variable area

  • 920378

    • CHARDEF supports all 512 screen codes (uppercase and lowercase)
    • Improvements to MONITOR handling of PC on entry
    • DSAVE explicitly rejects U12 device (not yet supported)
    • INFO command shows PAL/NTSC video mode
    • Improvements to SYS, LET

Release 0.95: ROM 920377

Release 0.95 was the factory installed release package for MEGA65s shipped in October 2022. It includes ROM 920377 and core 20221012.18,93d55f0.

Changes since release 0.9 (920287):

  • 920377: Change BASIC startup message
  • 920376: Fix GET bug
  • 920369: Fix DIM not executed issue
  • 920368: Fix no error report if trying to add string and numeric constant
  • 920367: RESET button triggers cold start, LIST uses blank character after line number
  • 920364: Implement VSYNC
  • 920363: Fix COPY bug
  • 920362: Add @dddaaannn's cursor save/restore
  • 920361: Allow the usage of the "save-and-replace" character @ in EDIT
  • 920360: Fix FN bug
  • 920359: Improve parameter check for FONT command
  • 920357: PEEKW -> WPEEK
  • 920356: Fix POKEW -> WPOKE
  • 920355: Fix IMPORT issue
  • 920354: Map byte arrays to screen memory
  • 920353: Fixed EDIT mode
  • 920352: fix COPY command
  • 920351: fix RAW mode flag for BLOAD
  • 920350: Debounce RTC readout
  • 920349: Fix INT()
  • 920348: PLAY & SOUND (improvements); BASIC-initiated sounds play in the background, do not block
  • 920347: CHARDEF; Allowed for PLAY command to use SID1+SID3 (on 6 voice channels), while SOUND command uses SID2+SID4 (on 6 additional voice channels)
  • 920342: More circle/ellipse improvements (?)
  • 920340: ESC X to toggle 40/80 column mode (?); Was this there before? Looks new here, but not documented
  • 920329: ELLIPSE and CIRCLE; These already existed (or at least they appear in the print manual.) Dunno what changed.
  • 920320: CBDOS bug fixes
  • 920319: Fix U2 bug
  • 920318: Fix of the bug: DS (Disk Status) was not reset to OK after reading it from the error channel.
  • 920316: No changes except the version number
  • 920314: Extend CBDOS pattern matching with # and $
  • 920313: Fix APPEND bug in CBDOS
  • 920311: Add partial support for D64 image files
  • 920310: Fix SLEEP
  • 920309: CBDOS optimisations
  • 920308: Fix ROM/FDC/XEMU issue with DIR U12
  • 920306: Suspend BASIC IRQ during SYS
  • 920304: Hassle free SYS command
  • 920303: Fix "Save And Replace" bug
  • 920302: DOT and LINE clip negative coordinates
  • 920301: LOCK & UNLOCK, fix CBDOS bugs
  • 920300: New number parser speeds up BASIC65.
  • 920299: Add commands BITSET and BITCLR
  • 920298: Add command INFO
  • 920297: Improve SIN, COS, TAN functions
  • 920296: Improve COPY command for internal floppy drive and SD-card images
  • 920295: Fix RENUMBER for line number 65535
  • 920294: Bug fixes and optimisation of CBDOS
  • 920292: CHDIR implemented.
  • 920291: The functions FNA() - FNZ() are now fast functions.
  • 920290: Fix MONITOR assembler to accept BEQ mnemonic. Patches now require using the older 910828 as the base instead of 911011.
  • 920289: Sprites can now be used in 320 x 200 bitplane graphics with their usual storage at $600 - $7ff
  • 920288: Pressing STOP at power on activates MONITOR, leaving it with X skips AUTOBOOT

Release 0.9: ROM 920287

Release 0.9 was the first release package, dated January 2022. It included ROM 920287 and core 20220109.11,1586ad4. This release was factory installed with MEGA65s that shipped in May 2022.

See this history of the MEGA65 ROM for change notes from the beginning (January 2021) to ROM 920376 (July 2022), including a few notes on the known Commodore prototype versions.