Since Emu68 JIT is not aware of surrounding hardware or peripherals attached to the machine (with only few exceptions) the configuration can be done only through the command line parameters. These can be set through the
cmdline.txt file placed on the boot FAT32 partition together with Emu68.img file.
The cmdline.txt is a one-line file which is passed directly into the device tree available on the M68k through a resource. It can be found in the
bootargs property of the
/chosen node like in the following example:
// The prototypes for devicetree.resource
APTR DeviceTreeBase = OpenResource("devicetree.resource");
/* Open /chosen node */
APTR key = DT_OpenKey("/chosen");
APTR property = DT_FindProperty(key, "bootargs");
CONST_STRPTR bootargs = DT_GetPropValue(property);
ULONG bootargs_len = DT_GetPropLen(property);
Now bootargs points to a **NOT** terminated character sequence which can be
searched for any necessary parameter.
Below are currently implemented options, grouped by the affected modules and/or functionalities.
sd.verbose=0 | 1 | 2
Adjust verbosity of the driver. Value
0is default one and it shuts off debug nearly completely. Value
1gives some more details from the driver, whereas value
2should be used only for debugging purposes since it reports every single BeginIO call.
sd.unit0=off | ro | rwChange the behaviour of sdhc-brcm.device unit 0. Default value is
rowhich means the unit is not hidden, but cannot be written to. Changing the value to
offdisables the unit 0 completely whereas
rwallows one to write data to it. Use with care, as Unit 0 of the device represents the entire card, including partition table and FAT32 boot partition.
sd.low_speedDisables 50 MHz clock even if the microSD card reports that the clock is supported. Setting this option disables SD card overclocking (see subsequent option).
sd.clock=numSelects the clock speed in MHz which will be switched on instead of default 50 MHz if the card supports the high-speed mode. The option has no effect if
sd.low_speedwas also applied.
The same set of options as in case of
emmc prefix in this case.
vbr_moveMoves VBR (base address for exception vector table) from CHIP to FAST ram. This setting improves the performance slightly, since the FAST ram on Emu68 is at least 500 times faster than CHIP, but reduces compatibility with old games and demos started from floppy drive drastically. However, system-friendly software as well as demos and games started through WHDLoad should not be affected.
vc4.mem=numSets size of VC4 memory reported to P96 subsystem to
numMB. Default is 16 in case of PiStorm build and 0 in all other Emu68 variants. Please note this is not the same as
gpu_memsetting in config.txt file. The latter is used to assign general purpose memory to the VPU.
one_slotForces a one-slot pistorm32 protocol resulting in slower write accesses to chipset and to CHIP memory
debugEnables debugging of the JIT engine. Every portion of m68k code translated to AArch64 will be shown in form of short statistics and binary dump of ARM code. Statistics include number of m68k instructions translated, resulting number of ARM instructions, mean ARM instruction number per m68k opcode and CRC32 checksum of translated memory block.
disassembleShows disassembled blocks in two columns. The left column contains m68k code disassembly whereas the right column is the AArch64 code. The two are aligned vertically so that the translated code can be assigned to every single m68k opcode properly.
async_logUse asynchronous log on separate ARM core with a 8 MB large ring buffer. Improves performance of m68k when debug is enabled.
fast_serialUse synchronous serial port running at a speed varying between 10 and 50 MBit instead of regular serial protocol at 921.6 kBit. Requires proper hardware such as e.g. FT232H.
buptest=numWhen Emu68 is starting it will perform a bus test of the PiStorm interface. A
numkilobytes of CHIP memory will be written with random patterns and subsequently will be read in many different ways with varying read sizes and data alignment. In case of error, which indicates some issues with PiStorm interface or connection to the Amiga, the test will stop and Emu68 will not start.
bupiter=numSets the number of iterations (of different randomised data patterns) of the bus test mentioned above.
limit_2gLimit the mapped ARM memory to two gigabytes. Useful on machines which offer more RAM and, because of that, confuse e.g. AmigaOS.
enable_c0_slowEnables “slow” memory in
enable_c8_slowEnables “slow” memory in
enable_d0_slowEnables “slow” memory in
move_slow_to_chipMaps 512K memory expansion of A500 to the CHIP ram range.
z2_ram_size=0 | 1 | 2 | 4 | 8Set size of Zorro II RAM expansion to 0 to 8 MB. Default is 8, but eventually has to be lowered if other Zorro II devices are installed in the system.
chip_slowdownEvery translated m68k opcode will have additional ARM instruction reading the opcode word from memory before executing it. Can improve compatibility of old software using busy loops for delay purposes.
cs_dist=1..8Adjust the distance between chip slowdown instructions. This option has effect only when
chip_slowdownis active, either by cmdline.txt or enabled with EmuControl tool. For a number
nspecified here the slowdown applies to every n-th instruction, only.
checksum_romRecalculates checksum of mapped rom. Might be useful in case of modded kickstart files with broken checksum.
copy_rom=256 | 512 | 1024 | 2048When Emu68 is starting the original Amiga ROM installed in your computer will be copied to fast ARM memory. The number determines size of the ROM image (in KB) which should be copied.
enable_cacheTurns on JIT cache in
CACRregister on startup. Useful in case of bare metal software started instead of AROS or AmigaOS ROM.
nofpuDisables the FPU unit of Emu68. All LineF opcodes related to FPU will trigger the exception.
swap_df0_with_df1Swaps DF0 with DF1 floppy drive.
swap_df0_with_df2Swaps DF0 with DF2 floppy drive.
swap_df0_with_df3Swaps DF0 with DF3 floppy drive.