Settings


The settings window appears directly after starting Frodo, or by pressing F10 while the emulation is running.

Disk Drives

The box “Drive Paths” has four fields, each corresponding to one of four emulated Commodore 1541 floppy disk drives with the drive numbers 8, 9, 10 and 11 (normally you only need drive 8). For each drive, there is a file selection button, an “Eject” button and a “Next Disk” button.

Frodo offers three different modes for drive emulation (see here for details):

The file selection button opens a dialog where you can choose a .d64/.x64/.t64/LYNX file to mount in the corresponding drive on the emulator. To select a directory for Directory Mode, choose any file within the directory that is not of one of those image file types.

Clicking on the “Eject” button unmounts the selected file or directory from the respective drive. When full 1541 emulation is enabled, the drive will behave like it has no disk in it, otherwise the drive will be disconnected entirely.

The “Next Disk” button only works in Disk Image Mode and changes the mounted .d64/.x64/.g64 disk image file to the next one in a series. Frodo tries to be a bit clever about figuring out what that “next disk” actually is. If the image files have names ending with patterns like “Disk 1”/“Disk 2”, “Side A”/“Side B”, “(1)”/“(2)”, etc. it is usually successful.

If “Enable Full 1541 Emulation” is turned on, the four emulated 1541s are disabled and replaced by a single 1541 emulation (drive 8) that only operates on .d64/.x64/.g64 files, but emulates the entire 1541 hardware and is compatible with most fast loaders and some forms of copy protection, at the expense of considerably slower disk access. If you have a .d64 with a program that doesn't load with the normal emulation (see above), you may have better luck with the full 1541 processor emulation instead.

With “Map / ↔ \ in file names” you control whether a '/' in C64 filenames will be translated to '\' and vice versa for Directory Mode drives. On many systems, the '/' character is used to access subdirectories, but since the C64/1541 doesn't support subdirectories, that character is a valid part of a C64 file name. This is a problem if a program wants to create a file with a '/' in it, because the host system would interpret the part before the '/' as a directory name and, finding no such directory, would return an error and the operation would fail. If you activate this checkbox all '/'s will transparently be translated into '\', so in directory listings the '/' will still appear. If you turn off this option, you can actually use the '/' to access files in subdirectories from the C64.

Video/Sound

With “Display Type” you can choose whether the emulation shall run in a window or in full-screen mode. You can also switch between modes while Frodo is running by pressing the Enter key on the numeric keypad.

“Initial Window Size” allows you to select the factor by which the emulation window is initially scaled up compared to the original C64 display resolution. The window can also be resized later while Frodo is running.

The “Color Palette” setting switches between two color schemes for the C64 display: The “Pepto” palette produces vibrant colors, while the “Colodore” palette is more desaturated but more closely matches what the original video display on a C64 looked like.

With "Display Sprites" you can switch the display of sprites on and off. This setting should usually be on, unless you want to analyze the sprite layer of a graphical effect on the C64.

“Detect Sprite Collisions” determines whether collisions between sprites among themselves, and between sprites and background graphics should be detected by the C64. Turning off collisions may make you invincible in some older games (sadly, your enemies are likely to become invincible, too :-/).

Frodo normally uses the lower border of the C64 display to overlay some information about the emulation speed (unless it is running at 100%) and a representation of the activity/error LEDs of the emulated disk drives. By deselecting “Show Speed and Drive LED Status” you can turn off this display if you find that it distracts from the pure C64 experience.

The “Sound Emulation” selection controls the type of sound output. “None” means no sound, “Software” turns on the software sound emulation. Under Linux, there is another option, “Catweasel” for using a hardware SID chip on a Catweasel MK3 board (you also need Catweasel kernel drivers for this).

The “Software” setting also gives you two choices for the kind of C64 sound chip to emulate: The 6581 (recommended) is the original SID chip, while the 8580 is a newer revision with some audible differences. In Frodo, the setting affects the audio filters and the sound of combined waveforms. Some newer C64 software (1990s onwards) may only sound properly with the “8580” setting, some software also gives you a choice which SID chip to use. If in doubt, choose “6581”.

The “Enable SID Filters” field enables the software emulation of the SID sound filters. Actual SID chips have quite some variance in the performance of their filters, and some C64 music may sound a little better with the filter emulation disabled.

Input

“Joystick Port 1/2” allows you to select which connected game controller you want to use for each of the two C64 joystick ports. Note that most C64 games use a joystick in Port 2. If you don't want to use game controllers, Frodo also offers a joystick emulation on the numeric keypad.

With “Swap Joysticks” you can swap the assignments of the two joystick ports without having to re-select the attached game controllers. If, for example, you only have one controller mapped to Port 2 but the game expects a joystick in port 1, then you can simply activate “Swap joysticks” and continue to use your already assigned controller.

Options

When the field “Limit Speed to 100%” is active, Frodo caps the speed of the emulation at 100% of that of an original C64. This is usually what you want when playing games.

With the setting “Fast Reset” you can bypass the memory test which the C64 normally performs on a reset, and which takes about three seconds to complete. Under emulation, this test is not necessary and resetting the C64 (F12 key) gets much faster when it is bypassed.

The “Expansion Slot” group allows you to attach various devices to the expansion slot of the emulated C64. Under “Memory Expansion” you can set the type and size of a RAM expansion module emulated by Frodo, or turn the emulation off (“None”). Very few C64 software actually uses a RAM expansion (operating systems like ACE and GEOS, some disk copy utilities, and the port of the “Sonic the Hedgehog” game, for example), so you can usually leave this at the “None” setting.

If the “Memory Expansion” is set to “None”, you can use the “Cartridge” file selection button to choose a .crt cartridge image file to attach to the C64. At the moment, Frodo only supports simple 8K and 16K game cartridges (that means no Ultimax, Action Replay, or other funny things). When attaching a new cartridge, Frodo will reset the C64 to allow the cartridge software to start properly. Click on the “Eject” button to remove the cartridge from the emulated C64 and return it to normal operation, ready to load disk-based games again.

Advanced

The settings in this group are only available in Frodo Lite.

“Cycles per line (CPU)” and “Cycles per Bad Line (CPU)” set the number of clock cycles available to the C64 CPU per normal raster line and per Bad Line. If a program shows flickering lines or graphical flaws you can try to slightly alter both values.

With “Cycles per line (CIA)” you can control the speed of the CIA timers. Entering a higher value increases the frequency of cursor blinking and key repeat. Some programs don't run correcly with the default value.

“Cycles per line (1541)” sets the number of cycles available to the 1541 processor emulation per raster line. There is normally no need to change this value. This setting has no effect if 1541 processor emulation is turned off.

The settings for the four “cycles” coming closest to an original PAL C64 are (63, 23, 63, 64).

The setting “Clear CIA ICR on write” is necessary to make some programs (such as the games “Gyruss” and “Motos”) run that would otherwise hang in an endless interrupt loop because they use an unusual technique to acknowledge CIA interrupts (sometimes by accident, it appears...). It should normally be turned off.

Menus and Other Buttons

Clicking “Start”/“Continue” or selecting the respective command from the “File” menu will close the settings window and start the actual emulation or return to it. Likewise, "Quit" will discard your changes to the settings and quit Frodo.

With “Create Disk Image File...” in the “File” menu you can create an empty .d64 image file if you need one, for example to save your progress in a game. You can mount the created image file in the “Drive Paths” settings.

Once the emulation has been started you can use the “Save snapshot...” command in the “File” menu to save the current state of the emulated C64 to a file which you can then restore later using the “Load Snapshot...” command.

Warning: The format of snapshot files is expected to change in future versions of Frodo, so don't get too attached to your saved snapshots.

The “SAM Monitor...” command in the “Tools” menu starts the SAM machine language monitor which allows you to inspect the state of the running C64 program.