IMPORTANT PSA! The v1.17 firmware on some Kawari large boards shipped from VGP recently contained a bug causing DVI video instability. If you received one of these devices, please flash the updated v1.17 firmware from the FIRMWARE page to correct the issue. I apologize for the inconvenience. Refer to FLASHING for instructions on how to update the firmware.

VIC-II Kawari is a hardware replacement for the VIC-II (Video Interface Chip II) found in Commodore 64 home computers. In addition to being compatible with the original VIC-II 6567/6569 chips, some extra features are also available. See REGISTERS.md

This repository contains an open source VIC-II FPGA core written in Verilog. Three PCB designs/configurations are possible ranging from (approximately) $30 BOM cost to $80 BOM cost.

The PCB interfaces with a real C64 address and data bus through the VIC-II socket on the C64 motherboard. The board can replace all the functions of a real VIC-II chip including DRAM refresh, light pen interrupts (real CRT only), PHI2 clock source for the CPU and, of course, video output.

Utility and Demo Disks - Utilty and demo disk download area
Forum Server - Discussions, ask questions
Discord Server - Chat about stuff, ask questions
Report Issues - File bugs/issues

Firmware Downloads | Flashing Guide | Jumpers | Programming

If you intend to fork VIC-II Kawari to add your own features, please read FORKING.md

Please note that the video options available depends on the board design and configuration:

'POV' Stands for Plain Old VIC and is meant to be nothing more than a VIC-II replacement with no extra features other than the ability to flash the device. Kawari-POV has never been produced but is possible using the Mini PCB design with some parts omitted.

For a chart breaking down all features available or missing for a particular board design, please see MODELS.md

The core is flexible and can be configured to support all three or any subset of these video options provided the hardware can support it.

By default, the DVI/RGB signals double the horizontal frequency from ~15.7khz to ~31.4khz (for 2X native height). The horizontal resolution is also doubled to support the 80 column mode. The spartan boards support turning off scaling for both DVI and RGB output. The Trion boards no longer support 1x scaling (either width/height). (NOTE: Turning off horizontal scaling will prevent hires modes from working properly.)

The Trion board RGB firmware has resolutions identical to the spartan table above.

There are two firmware options for DVI output on the Trion boards but there are trade-offs to be aware of.

If you are not interested in the extended features and are having trouble with the PAL mode on your monitor, try the alternate firmware. The modes are summarized below:

The default DVI firmware (full 2x/2Y resolution) is reduced to the following values:

Video	Sample	Notes
NTSC		Less border area but new hires modes fully defined. Non-standard resolution may confuse some monitors.
NTSC(Old)		Less border area but new hires modes fully defined. Non-standard resolution may confuse some monitors.
PAL-B		Less compatibility but new hires modes fully defined. Non-standard resolution may confuse some monitors.

If your monitor does not support the non-standard PAL-B mode, see 'Alternate Trion DVI Firmware' below.

The default Trion DVI firmware may not work on all monitors/TVs as it outputs resolutions that are not standard. Also, the video tends to be more 'stretched' even using a 4:3 aspect ratio setting on the monitor. If your display doesn't show the PAL video mode, you can try an alternate DVI firmware with a mode closer to the 720x576 standard. This is more likely to work for older TVs/monitors. However, please be aware the C64's native video modes are scaled by 1.8x rather than 2x to get a better aspect ratio and more border space. Although regular C64 video modes will look okay, the Kawari's extended hi-resolution modes (80 column, 640x200) will look pixelated as those modes are effectively downscaled 10:9. This an unfortunate trade-off to using this video timing.

Video	Sample	Notes
NTSC		More border area but new hires modes will look pixelated. Regular C64 video modes not affected by scaling. More compatible resolution.
NTSC(Old)		More border area but new hires modes will look pixelated. Regular C64 video modes not affected by scaling. More compatible resolution.
PAL-B		Better compatibility but new hires modes will look pixelated. Regular C64 video modes not affected by scaling. More compatible resolution.

Both the Spartan & Trion PCBs have an unpopulated 10 pin analog header (1 +5V, 6 signal, 3 GND) that can wired to a monitor with a custom built cable.

+5V CLK GND RED GRN
GND VSY HSY BLU GND

For 1080/1084-D monitors, a CSYNC option can be enabled to output composite sync over the horizontal sync pin. 1084-S monitors use the default separated HSYNC and VSYNC signals.

NOTE: The CLK pin (dot clock) is disabled as it is not necessary for analog connections. If you need it, it can be enabled with a firmware update.

   _______       Pin#      Signal
  /   3   \      Pin 1     G  Green
 / 2     4 \     Pin 2     HSYNC Horizontal Sync
|     6     |    Pin 3     GND Ground
 \ 1  _  5 /     Pin 4     R  Red
  \__/ \__/      Pin 5     B  Blue
                 Pin 6     VSYNC Vertical Sync

                 Pin  Name     Signal
_____________     1   GND      Ground
\ 1 2 3 4 5 /     2   GND      Ground
 \_6_7_8_9_/      3   R        Red
                  4   G        Green
                  5   B        Blue
                  6   I        not used
                  7   CSYNC    Composite Sync (Enable CSYNC option in config)
                  8   HSYNC    not used
                  9   VSYNC    not used

The x2 native width video modes work on 1080/1084 monitors (requred for 80 column/hires modes).

A SCART adapter should be possible but has not been built/tested.

You can try the xrandr helper scripts inside monitor_tests directory in this repository. These are scripts meant to test the 60hz/50hz modes from your Ubuntu Linux machine. See README.md for a description on how to use them.

1. May not work on older monitors or TVs (non-standard resolutions)
2. You won't get a 4:3 aspect ratio unless your display has the option
3. You may have to turn off the display or use an HDMI switch to boot the C64
4. Using the motherboard oscillator may result in loss of sync

1. The resolution/timing the board outputs is not a standard resolution. Some older TVs/monitors may not sync to it. Some HD Capture cards only accept standard resolutions as well (like 720p or 1080p) and will also not sync.

2. The display will be horizontally stretched on most HDMI displays. You will not be able to get a perfect 4:3 aspect ratio. Some displays have a aspect ratio option that can yield a better result. There are no plans to do any processing on the output (i.e. scaling).

3. HDMI monitors can power the FPGA core through the HDMI cable. This prevents the core from booting properly (or sometimes booting at all). It's an unwanted side-effect of driving the TMDS lines directly from the FPGA core. This device is not an HDMI device, it is DVI over an HDMI connector. A buffer IC is required to avoid this but would add more cost to the board. The work around is to either power off the monitor or use an HDMI switch.

4. The quality of the mother board clock is not sufficient to derive the 40x dot clock required for the DVI signals. It appears the high jitter on the crystal is the cause. The motherboard clock was never meant to go through a clock multiplier to high frequencies. This appears to cause sync loss especially on NTSC boards. For this reason, the on-board oscillators should be used to drive the digital display modes.

The 'Large' and 'Mini' models can replace the 6567R8(NTSC),6567R56A(NTSC),6569R3(PAL-B),6569R1(PAL-B) models. They can assume the functionality of either video standard with a simple configuration change followed by a cold boot. This means your C64 can be both an NTSC and PAL machine. (PAL-N / PAL-M are not supported but it can be added with some hardware modifications.) The 'POV' model cannot behave as 'old' chip models (R56A/R1) and are fixed to either a 6567R8 or 6569R3.

The 'Mini/POV' boards will fit into revisions 250407, 250425, 326298 & KU-14194HB. For 250425 boards, the RF sheild must be removed. For 250407, 326298 and KU-14194HB, the 'top' cover of the RF sheild compartment must be removed.

The 'large" board will fit into revisions 250407, 250425, 326298 & KU-1419HB provided an extra socket is included to give the PCB enough height to clear some of the clock circuit components. However, if present, the RF sheild surrounding the video circuitry will prevent an HDMI cable from being plugged in even with an extra socket. For better HDMI port access, the large board is recommended for boards that do not have an RF sheild surrounding the video circuit. Also, it is better if the RF modulator is unpopulated or replaced with a RF modulator bypass board. This leaves room for a cable to be plugged in and exit the machine through unused holes at the back. Strain relief is up to the user.

Although the board will (mostly) function if plugged into a C64-C 'short' board (i.e. 250469), the current versions of VIC-II Kawari are not recommended for these motherboards.

1. It is difficult to close the machine. The 'Mini' PCB sits too high off the motherboard which presses up on the sheilding (required to be installed due to keyboard support brackets being attached). The large also requires an extra socket to clear some motherboard components and causes the same issue with the sheild. If you are willing to replace the sheild with 3D printed keyboard support brackets (or other solutions), you may be able to get it to fit into a closed machine. However, this has not been tested.

2. The 8562/8565 CAS/RAS timing is slightly different than the older generation 6567/6569 chips. You can try flashing an alternate firmware that adjusts the timing. However, there are still some issues that can cause some games/demos to fail. For this reason, I am not recommending VIC-II Kawari for C64-C short boards.

NOTE: The VDD pin is not connected so there is no voltage compatibility issue like with the real 8562/8565 models. It won't damage the Kawari to plug it into a C64-C 'short' board. You may run into the issues described above, however.

The 6567R56A composite signal is known to be worse than the 6567R8. The cycle schedule (and hence timing) is slighly different in the 6567R56A. It generates a signal slightly out of range from the expected 15.734khz horizontal frequency for NTSC (it generates 15.980khz instead). Some composite LCD monitors don't like this and even the real chips produced unwanted artifacts on those types of displays. You will get the same unwanted artifacts from a VIC-II Kawari producing composite video when configured as a 6567R56A. Most CRTs, however, are more forgiving and you may not notice the difference. Some TVs still show a bad picture. When using DVI or RGB output, this is of no concern as long as your monitor can handle the frequency (the image will look just as good as any other mode). There may be some NTSC programs that depend on 6567R56A to run properly due to the cycle schedule but I'm not aware of any. The default config defines only 5 luminance levels for the 6567R56A.

There are subtle differences between the PAL-B revisions mostly to do with luminance levels. I included the 6569R1 as an option. Keep in mind the default luma config has only 5 luminance levels instead of 8 and also has a light pen irq trigger bug. (There's nothing stopping you from defining 8 lumanance levels for the 6569R1 though).

It is, in theory, possible to re-purpose one of the video standards to be a 6572 (South America PAL-N). It would require a firmware change and the board would have to be configured to use the motherboard's clock (or one of the oscillators changed to match PAL-N frequency). Either NTSC or PAL-B could be replaced with PAL-N. As far as I can tell, the only reason to do this would be to get real Argentinian CRTs/TVs to display a composite signal correctly while being (mostly) compatible with NTSC software. (This is a lower priority project but if someone else wants to take on the challenge, it could appear as a fork.)

This depends on how the VIC-II Kawari PCB has been populated and configured. The 'Large' and 'Mini' boards come with on-board oscillators for both NTSC and PAL-B standards. In that case, the motherboard's clock circuit can be bypassed. However, the board can be configured to use the motherboard's clock for the machine's 'native' standard via jumper config. In that case, one of the two video standards can be driven by the motherboard's clock. Please see Limitations/Caveats below regarding pin 6 of the cartridge port. The 'POV' model must use the motherboard's clock and cannot switch video standards. Refer to the table below for C.SRC jumper settings.

For 'Large' and 'Mini' boards, the C.SRC jumpers let you select the clock source for the two video standards the board supports. By default, both video standards are driven by on-board oscillators (if the board has been populated with them). However, you have the option of using the machine's 'native' clock source for one of the video standards. This is an option in case some specialty cartridges require the use of Pin 6 on the cartridge port. See Limitations/Caveats

Here is a table describing the valid jumper configurations:

The board will function without any modifications to the motherboard. If you can find a way to get a video cable out of the machine, there is no reason to modify the machine. However, it is much easier if the RF modulator is removed. The hole previously used for the composite jack may then be used for an HDMI or VGA cable. Otherwise, there is no practical way for a video cable to exit the machine unless you drill a hole or fish the cable out the casette or user port space.

IMPORTANT! Strain relief on the cable is VERY important as it exits the machine. No matter the solution, it is imperative the cable not be allowed to pull on the board while it is seated in the motherboard socket.

To measure accuracy, I use the same suite of programs VICE (The Versatile Commodore Emulator) uses to catch regressions in their releases. Out of a total of 280 VIC-II tests, 280 are passing (at least by visual comparison).

I can't test every program but it supports the graphics tricks programmers used in their demos/games. Refer to the Hardware/Software compatibility matrix below. Although perhaps not perfect, it is safe to say it is a faithful reproduction of the original chips.

That's a matter of opinion. Some people consider an FPGA implementation that 'mimics' hardware to be emulation because some behavior is being re-implemented using a high level hardware description language. But it's important to note that the PCB is not 'running' a program like you would on a PC. The PCB is providing a real clock signal to drive the 6510 CPU. It's also generating real CAS/RAS timing signals to refresh DRAM. It is interacting with the same address and data bus that a genuine chip would.

Yes. The pixel perfect look on an HDMI monitor will resemble an emulator. There is an option that will render ever other line with half brightness giving a raster line effect. This makes the picture look slightly darker though. Other than that, there is no effort to make digital video look like a CRT. If you want the look of a CRT, you should chose the VGA or composite options and use a real CRT. Also, the resolution will not match an HDMI monitor's native resolution so there will always be some scaling taking place.

There is no frame buffer for video output. However, there is a single raster line buffer necessary to double the 15khz horizontal frequency. Although this adds a very small delay, it is a tiny fraction of the frame rate and is imperceivable by a human. For DVI, any additional latency will be from the monitor you use. Most TVs have a 'game mode' that turns off extra processing that can introduce latency and it is highly recommended you use that feature.

The video signals are output at native resolution (or 2x) and since there is no frame buffer, the aspect ratio of the image cannot be adjusted. It will be up to your monitor/TV to support 4:3 aspect ratio to display something that doesn't look 'stretched'. I have no plans on making the DVI/HDMI image look like an analog display.

Yes. However, light pens will only work using a real CRT with composite. (LCD/DVI/HDMI or even VGA monitors will not work with light pens.)

If you need a VIC-II to replace a broken one, you should just buy one off eBay. This project is for fun/interest and would certainly cost more than just buying the real thing. However, there are some advantages to using VIC-II Kawari ('Large/Mini' models):

• No 'VSP' bug
• Configurable color palette (262144 RGB color space, 262144 HSV color space)
• No need for a working clock circuit
• Can software switch between NTSC and PAL-B
• Optional NTSC/PAL-B hardware switch
• Four chip models supported (6567R56A, 6567R8, 6569R1, 6569R3)
• An 80 column mode and new graphics modes
• An 80 column Novaterm driver
• Some fun 'extras' to play around with
• It's not an almost 40 year old device that may fail at any time

Also, since the core is open source, hobbyests can add their own interesting new features (i.e. a math co-processor, more sprites, more colors, a new graphics mode, a display address translator, etc) See FORKING.md for some a list of possible add-ons.

Each of the Commodore 64's 16 colors can be changed for preference. For RGB based video (DVI/VGA), an 18-bit color space is available (262144 colors). For composite (luma/chroma) video, a 18-bit HSV color space is available (262144 colors). The color palette can be saved and restored on a cold boot and is configurable for each chip separately.

A true 16 color 80 column text mode is available. This is NOT a soft-80 mode that uses bitmap graphics but rather a true text mode. Each character cell is a full 8x8 pixels. An 80 colum text screen occupies 4k of kawari video memory space (+4k character definition data). A small program (2k resident at $c800) can enable this for the basic programming environment. The basic text editor operates exactly as the 40 column mode does since the input/output routines are simply copies of the normal kernel routines compiled with new limits. This mode also takes advantage of hardware accelerated block copy/fill features of VIC-II Kawari so scrolling/clearing the text is fast.

NOTE: 40 column BASIC programs will not necessarily run without modification in the 80 column mode. If the program uses print statements exclusively, then there's a good chance it will work. If it uses POKEs to screen memory, it will have to be modified.

NOTE: The 80 column display was not intended for TVs or low resolution monitors. The mode will function using a composite signal but the bandwidth is too low and you will not get a sharp display. You may get a more usable image using a custom s-video cable (and possibly an upscaler).

A Novaterm 9.6c 80 column video driver is available. Use this driver with a user port or cartridge modem and relive the 80's BBS experience in 80 columns on your C64!

In addition to the 80 column text mode, three bitmap modes have been added for you to experiment with:

320x200 16 color - Every pixel can be set to one of 16 colors.
640x200 4 colors - Every pixel can be set to one of 4 colors.
160x200 16 colors - Every pixel can be set to one of 16 colors.

Low-res sprites will show up on the hi-res modes. However, they behave according to low-res mode rules. That means their x-positions are still low resolution. Background collisions will trigger based on hi-res screen data, but cannot detect collisions at the 'half' pixel resolution. Sprite to sprite collisions should work as expected. This was a compromise chosen between adding new hires sprite support (taking up a lot of FPGA space) and having no sprites at all. For the 320x200 and 640x200 bitmap modes, a pixel is considered to be background if it matches the background color register value. Otherwise, it is foreground.

There is an additional 64K of video ram. This is RAM that the video 'chip' can access directly for the new hires modes. It can also be used to store data and there is a DMA transfer function that can copy between DRAM and VRAM quickly without using CPU resources.

Hardware divide and multiply registers were added to avoid costly loops. Some programs can be modified to take advantage of these registers.

A blitter is availble to copy rectangular regions of memory quickly without using the CPU. There are also block copy and fill routines that can move or fill video ram. These features are useful for the new hi-res modes.

A configuration utility is provided which allows you to change the chip model at any time. Changes to the chip model will be reflected on the next cold boot. This means you can switch your C64 between NTSC and PAL-B with ease AND without opening up your machine!

The full featured config utility takes longer to load, so a smaller quick switch program dedicated to changing the chip is also included.

The 'switch' header on the PCB will toggle the chip model between the saved standard (switch open) and the opposite standard (switch closed). Please note that the 'older' revisions and 'newer' revisions will switch with each other.

Simply plug VIC-II Kawari into the VIC-II socket. No modifications are necessary.

In this configuration, the RF modulator is removed or replaced with a device that continues to generate the composite signal for the video output port. The hole previously used for RF out is used for a custom VGA cable connected to the header on Kawari.

NOTE: Strain relief is important!

NOTE: You can get away without removing the RF modulator but then you will have the challenge of getting the VGA cable out of a closed machine. I don't recommend drilling holes but this is an option. Another option is to fish the cable out the user port opening, if you don't plan on using any user port connections.

In this configuration, the RF modulator is removed or replaced with a device that continues to generate the composite signal for the video output port. The hole previously used for RF out is used for an HDMI cable connected to the Kawari.

NOTE: Strain relief is important!

NOTE: You can get away without removing the RF modulator but then you will have the challenge of getting the cable out of a closed machine. I don't recommend drilling holes but this is an option. Another option is to fish the cable out the user port opening, if you don't plan on using any user port connections.

You can reset the board by temporarily shorting the jumper pads labeled 'Reset' while the device is powered on. The background and border color will turn white to let you know a reset has been detected. Then cold boot. This will prevent the device from reading any persisted settings. The default palette will be used for all models. After a config reset, the next time you run any configuration utility, it will prompt you to initialize the device again.

Not really. That's up to you. That's why the project is open source. Consider my 'MAIN' variant one possibility of what you can do with the device. However, since my features take up practically all the fabric, you would most likely have to disable some of my 'extras' in favor of yours.

The FPGA can be powered by the monitor through the HDMI cable and even though the C64 is powered off, the video card continues to run and hold the most recent color register changes. The solution is to turn off your monitor for a few seconds and then turn on the C64/monitor again. (Or use an HDMI switch). This only happens if you are using the extended features. The same is true for hi-res modes. If you find you are 'stuck' in a hires mode, you need to cold boot (for real).

Same reason as above. Kawari detects the switch only after a cold boot but if your monitor is still providing power to the board, it's not really cold booting. Workaround is described above. The same problem will happen for other 'cold boot' settings.

As noted above, the DVI resolutions used are not standard and may not sync or display properly on all monitors. This table keeps track of known issues.

Please note that if you change color registers or enable hi-res modes, Kawari will not revert back to the default palette or lo-res modes with a soft reset (or even RUN/STOP restore). If you want the Kawari 'Large' model to detect soft resets, you can connect the through hole pad labeled RST in the upper left corner of the board to the 6510's RESET pin (or any other RESET location) using a jumper wire and grabber. The 'Mini' and 'POV' models cannot detect resets.

A cartridge that uses the DOT clock signal on pin 6 may not work when the clock source is set to the on-board oscillator. The signal that reaches pin 6 of the cartridge port comes from the motherboard clock circuit and will likely be out of phase/sync with the clock generated by the on-board oscillator. In this case, you can configure your Kawari to use the motherboard's 'native' clock instead of the on-board oscillator. Note, however, that only the machine's 'native' video standard will work with such a cartridge. Since the vast majority of cartridges do not use pin 6, this should not be a problem for most users. A list of cartridges that are known to have problems may appear here in the future.

The Pi1541 has a feature that displays the IEC bus information to its display. This can interfere with tight timing requirements on some demo fast loaders (even on a genuine VIC-II chip) and can lead to corrupted data loaded into memory. If you are experiencing random crashes on demos like 'Uncensored', 'Edge of Disgrace' or similar demos, this is likely the cause. It is recommended you turn this feature off by adding 'GraphIEC = 0' to your options.txt. (I also turn off the buzzer option).

VIC-II Kawari was built to be detected, flashed and re-configured from the C64 main CPU. To prevent a program from (intentionally or accidentally) 'bricking' your VIC-II Kawari, some functions can be locked from programmatic access.

See REGISTERS.md for a description of the lock jumpers.

By default, flash operations are DISABLED. This means you must physically remove the jumper on Pin 1 to allow the flash utility to work. (It is recommended you put the jumper back after you've flashed the device.)

Also by default, persistence (extended register changes persisting between reboots) is ENABLED. Once you've set your preferred color scheme or other preferences with the config apps, you can remove the jumper on Pin 2 to prevent any program changing them without your knowledge/permission. Programs will still be able to change colors. But they won't be able to save them.

Access to extension registers (extended features) are ENABLED by default. If you want your VIC-II Kawari to function as a regular 6567/6569 and be undetectable to any program (including Kawari config apps) then removing the extension lock jumper on Pin 2 will do that. (NOTE: That includes being able to software switch the video standard. However, a hardware switch will still work.)

Without the lock jumpers, here are some ways a misbehaving program can make it look like your VIC-II Kawari has died:

1. erase the flash memory making the device un-bootable (must be restored via JTAG/SPI programmer)
2. change all colors to black and save them, making it look like a black screen fault (restored by shorting CFG jumper pad)
3. change the hires modes to a resolution incompatible with your monitor, again making it look like a black screen fault (restored by shorting CFG jumper pad)