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VIC-II Kawari

What is VIC-II Kawari?

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. The bitstream is generated by the ISE 14.7 toolchain from Xilinx and is flashed to compatible hardware. The hardware is available for purchase.

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.

Forking VIC-II Kawari?

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

What kind of video output options are there?

The core supports these video options:

DVI (i.e. over an HDMI connector)
Analog RGB (i.e VGA or RGB for a 1084 monitor) using a custom cable
    R,G,B - .7Vp-p (75 ohm termination)
    H,V   - TTL
Luma/Chroma (later mixed by the C64's RF modulator for composite video)

The core can be configured to support all three or any subset of these options. 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. However, the resolution scaling can be turned off for both width and height.

More video stuff

The DVI video modes are not standard and may not work with older monitors/TVs or capture cards. The 15khz modes require a monitor that can handle that horizontal refresh rate. If the device is configured for 15khz, DVI will not work.

The PCB has 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.

FEMALE 6-PIN PORT AS VIEWED FROM REAR OF 1084-S

   _______       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

MALE 9-PIN PORT AS VIEWED FROM REAR OF 1080/1084-D (Analog RGB Mode)

                 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.

How can I find out if my VGA/DVI/HDMI monitor supports the video?

TODO : xrandr or windows equiv to test monitor

What chip models can this replace?

It can replace the 6567R8(NTSC),6567R56A(NTSC),6569R3(PAL-B),6569R1(PAL-B) models. It 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.)

Will this work in C64-C (short board) models?

It will function if plugged into a C64-C 'short' board. The VDD pin is not connected so there is no voltage compatibility issue like with the real 8562/8565 models. Keep in mind that the board will behave as a 6567/6569 even when replacing a 8562/8565 (the differences are minor).

Isn't the quality of 6567R56A composite video bad?

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.

What about the 6569R4/R5?

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).

What about the 6572?

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.)

Do I need a functioning clock circuit on my motherboard?

This depends on how the VIC-II Kawari PCB has been populated and configured. VIC-II Kawari boards can come with on-board oscillators for both NTSC and PAL-B standards. In that case, the motherboard's clock circuit is not used. However, the board can be configured to use the motherboard's clock for the machine's 'native' standard. 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. Refer to the table below for C.SRC jumper settings.

How do the C.SRC jumpers work?

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:

Do I need to modify my C64 motherboard?

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.

How accurate is it?

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 KNOWN_ISSUES.md doc for a list of programs and/or demos that are known to have issues. Although perhaps not perfect, it is safe to say it is a faithful reproduction of the original chips.

Is this emulation?

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.

Will digital video make my C64 look like an emulator?

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.

Will DVI/VGA add delay to the video output?

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.

Do light pens work?

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.)

This is more expensive. Why not just buy a real one?

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:

• 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 available
• Four chip models supported (6567R56A, 6567R8, 6569R1, 6569R3)
• An 80 column mode and new graphics modes
• An 80 column Novaterm driver
• 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.

What extra features are available?

A configurable color palette

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.

An 80 column text mode

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.

Novaterm 9.6c 80 column driver

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!

New graphics modes

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

640x200 16 color - Every 8x8 cell can be one of 16 foreground colors or the background color.
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.

Notes about sprites in hires-modes

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.

Software switch between PAL-B and NTSC

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.

Hardware switch between PAL-B and NTSC

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.

What are the installation options?

Composite - No mod

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

VGA + RF Modulator Removal or Replacement

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.

DVI + RF Modulator Removal or Replacement

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.

Config RESET

You can reset the board by temporarily shorting the jumper pads labeled 'Reset' while the device is powered on. Then cold boot. (It's difficult to tell whether you've shorted them so you may have to try a couple times.) 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.

Limitations/Caveats

Cartridges that use DOT clock pin (pin 6)

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.

Pi1541

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).

Function Lock Jumpers

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)
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)