8.3 KiB
Configuring the build
It's not possible to provide ROM builds that suit everyone needs - therefore configuration files were introduced, few predefined configurations are provided with sane defaults:
Just edit them and recompile the project. To enable particular option - uncomment it by removing leading // from before #define directive (as you probably guessed, commenting out disables it). Some options are followed by constants - you can change them too to further fine-tune the build.
Note however, that features do not came for free - enabling them needs some additional ROM space (in BASIC segment, in KERNAL segment, or in both), which is VERY limited on the target machines. Some options might be unavailable for speecific targets - read the comments in the configuration files. Some options might also carry compatibility and/or performance hit - so choose wisely.
Hardware platform and variant
CONFIG_PLATFORM_COMMODORE_64
Commodore 64 is the only hardware platform available now - and the main one, as the Open ROMs API is meant to be compatible with the Commodore 64.
Since Open ROMs is highly modular, it should be possible to add other platforms in the future (like 8-bit Atari computers or Commander X16), if they share the following common characteristics:
- MOS 6502 CPU or compatible
- 8KB ROM area
$A000-$BFFF - 8KB ROM area
$E000-$FFFF
CONFIG_VARIANT_GENERIC
If you don't know which variant to choose - select this one.
CONFIG_VARIANT_MEGA_65, CONFIG_VARIANT_ULTIMATE_64
Select if you are using appropriate motherboard.
Processor instruction set
CONFIG_CPU_MOS_6502
Choose if your CPU only supports the original MOS Technology 6502 instruction set, like:
- MOS 6510 - used in the Commodore 64
- MOS 8500 - used in the Commodore 64C
- MOS 8502 - used in the Commodore 128
If unsure - select this one.
CONFIG_CPU_WDC_65C02
Choose if your CPU supports the Western Design Center 65C02 instruction set, like:
- WDC 65C02 - used in the Turbo Master accelerator
It enables some speed/size code optimizations.
CONFIG_CPU_CSG_65CE02
Choose if your CPU supports the Commodore Semiconductor Group 65CE02 instruction set, like:
- CSG 65CE02
- CSG 4510 - microcontroller used in the Commodore 65 prototypes
It enables some speed/size code optimizations.
CONFIG_CPU_WDC_65816
Choose if your CPU supports the 16-bit Western Design Center 65816 instruction set, like:
- WDC 65C816 - used in the Flash 8 accelerator
- WDC 65C816S - used in the SuperCPU accelerator
It enables some speed/size code optimizations.
Memory model
Different layouts of memory are possible - but they can be selected at compile time only.
CONFIG_MEMORY_MODEL_38K
Memory model the original machine uses - memory available for BASIC ends at $9FFF, just before the first block of ROM. The fastest and the most compatible, but gives the least memory for BASIC. If unsure - select this one.
CONFIG_MEMORY_MODEL_46K and CONFIG_MEMORY_MODEL_50K
Planned for the future - not available yet.
CONFIG_MEMORY_MODEL_60K
Uses RAM under BASIC, I/O and KERNAL, takes over $C000-$CFFF area requires special helper routines installed in $2A7-$2FF area (normally unused and free for the user). Gives the most free memory for BASIC programs, but it's the slowest and the least compatible model.
Comparing to standard memoryy model, it needs about 180 bytes in BASIC segment and 80 bytes in KERNAL segment - at the moment of doing the test, these values are expected to change often.
Multiple SID support
The SID is a sound chip - original machine had one installed. However, mods exists to add more of them for improved sound capabilitiee. Emulators and FPGA machines typically allow to simulate more than one too. Unfortunately, there is no standard regarding how these additional chips are visible in the processor address space, and there is no sane way to detect it - thus, it has to be configurable.
The SID support in the ROM is very limited - it only disables the sound during startup or warm restart (when STOP+RESTORE is pressed or BRK assembler instruction is executed).
CONFIG_SID_2ND and CONFIG_SID_3RD
Each of them add support for one additional SID - addresses should be given in CONFIG_SID_2ND_ADDRESS and CONFIG_SID_3RD_ADDRESS, respectively.
Each of these options needs 8 bytes in KERNAL segment.
CONFIG_SID_D4XX and CONFIG_SID_D5XX
Cause the system to support SIDs in $D4xx and $D5xx ranges, respectively.
Each of them needs a couple of bytes in KERNAL segment - but they can share some code, and $D4xx range support replaces the standard $D400 address handling, so exact amount depends on the exact configuration.
Keyboard
Original keyboard support routine is just horrible. It does nothing to prevent ghosting - press A+S+D at the same time - it prints F. Try to use joystick connected to control port 1 - it outputs phantom characters. The Open ROMs provides much more sophisticated routines to prevent such problems.
CONFIG_LEGACY_SCNKEY
Uses old Open ROMs keyboard scanning routine, which is basically example routine by TWW/CTR, hacked to work within Kernal. It's greatest advantage is multi-key rollover, it's disadvantages - it's much less compatible (uses several bytes of memory which are normally free for user software - thus, it is considered legacy for now), does not support all the system variables (RPTFLG and KEYLOG are unsupported), and ignores the configuration options - this can be changed, but it requires some effort.
Needs 70-250 more space in KERNAL segment (depending on the features enabled for current default routine). If unsure - disable.
CONFIG_KEYBOARD_C128
Allows to use additional keys found on the C128 keyboard.
Needs 128 bytes more space in KERNAL segment. If unsure - disable.
CONFIG_KEY_REPEAT_DEFAULT
Enables key repetition by default during the startup (sets RPTFLG).
Needs 5 bytes more space in KERNAL segment.
CONFIG_KEY_REPEAT_ALWAYS
Enables the key repetition and ignores RPTFLG.
Saves 22 bytes from KERNAL segment.
CONFIG_KEY_FAST_SCAN
Performs somee speed optimizations in the keyboard scanning routine, at the eexpense of some more ROM space.
Needs 13 bytes more space in KERNAL segment. Only disable if you are running out of ROM space.
CONFIG_JOY1_CURSOR and CONFIG_JOY2_CURSOR
Joystick movement also moves the cursor.
Needs about 65 bytes of ROM space to handle both joysticks.
Eye candy
CONFIG_BANNER_SIMPLE, CONFIG_BANNER_FANCY, CONFIG_BANNER_VARIANT
Select startup banner - either a simple one, or with some colorful elements. CONFIG_BANNER_VARIANT heavily depends on the selected hardware target, not all targets support it.
Richer banners need more BASIC segment, varies between hardware variants.
CONFIG_BANNER_PAL_NTSC
If enabled, prints video system on startup banner. Eye candy only.
Feature needs some bytes in BASIC (depending on banner type) and about 25 bytes in KERNAL segment.
Software features
CONFIG_PANIC_SCREEN
If enabled, certain fatal errors will produce a nice bluescreen instead of just resetting the machine.
Feature needs over 100 bytes in KERNAL segment. If unsure - enable.
CONFIG_DOS_WEDGE
If enabled, a simple DOS wedge is available from the direct mode - supports @<drive_number>, @<command>, @$, @$<params> and @ commands.
Feature needs about 330 bytes in BASIC segment. If unsure - enable.
CONFIG_BCD_SAFE_INTERRUPTS
On the most widespread CPUs the D flag is not cleared upon entering interrupts. Since the original Kernal does not clear it either, it's not safe to use BCD processor mode without disabling the interrupts first. This option makes sure the D flag is disabled at the start of the interrupt - this allows some optimizations in the code.
Feature needs 2 bytes in KERNAL segmment (for CPUs needing the patch), but at the same time allows optimizations allowing to gain some more bytes. If unsure - enable.
Debug options
Options in this section are for debug purposes only. If unsure - disable.
CONFIG_DBG_STUBS_BRK
Replaces RTS stubbed routines implementation with one causing a break.
CONFIG_DBG_PRINTF
Makes printf routine available.