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Yahoo group chameleon_64

FPGA examples on github https://github.com/pwsoft/fpga_examples

Individual Computers http://icomp.de


Turbo Chameleon FAQs


I still use a tv or svideo monitor, can the Chameleon be used without a VGA monitor?

Yes, although a few features of the cart will be unavailable. The 1541 drive emulation, freezer, clockport, MMU, REU and even the turbo are usable. Even with turbo mode enabled the VIC-II screen will be active and usable.

How can the VGA display the C64 screen?

Inside the Chameleon is a replica of the VIC-II chip. All register updates and memory accesses are send to both the original VIC-II chip and the replica. This "digital-cloning" approach gives much better VGA display quality compared to sampling and upscaling the composite signal.

How does the Chameleon deal with C128 machines?

The current firmwares (Beta-6 and Beta-7) are definitely NOT compatible with the C128 at all! Please, do not try as bus-conflicts will occur, which can cause damage to components inside the C128.

How does the Chameleon deal with SX-64 machines?

Chameleon is fully compatible with a SX-64 machine. On some machines the copying of the kernal ROM doesn't work. This option can be disabled in the menu until a fix is implemented.

How does the Chameleon deal with C-One machines?

There is a port of the Chameleon core for the C-One and can be downloaded for free. This replaces the FPGA-64 core (the PAL and NTSC C64 emulation core). The cartridge itself will NOT function correctly when placed in the C-One.

Is there SCPU (Super-CPU) / Flash-8 compatibility planned for the turbo mode?

No, the 6510 code comes from my FPGA-64 project. We don't have a 65816 compatible emulator yet. Also getting reliable 20Mhz cycle-exact operation with SDRAM is not easy. Especially as the VGA frame buffers, diskdrive emulation and REU are also using the SDRAM at the same time. The other issue is software support. The SCPU has additional ROMS that can't be copied without a license.

How fast is the 6510 based turbo?

Between 10 to 14 times faster for tight loops that only access memory (e.g. decrunchers) and between 4 and 6 times for I/O heavy apps. Basic programs run about 12 times faster on average.

Isn't the 6510 a bit limiting with its 64 Kbyte memory range, making the Chameleon a bankswitching nightmare?

Bankswitching is indeed supported (and sometimes necessary). You can for example map different kernals in the E000-FFFF area. Also rom cartridges at 8000-9FFF can be emulated with the bankswitching logic. A MMU block allows the 6510 to access all of the 32 Mbyte memory in 4 Kbyte blocks, but some areas are reserved for the freezer cartridge emulator and Chameleon configuration menu. The emulated REU can access large amounts of memory very quickly and transfer it into the lowest 64 Kbytes where the 6510 can access it. GeoRAM emulation can map 256 bytes out of a 4 Mbyte buffer into the C64 memory at DE00h-DEFFh.

Is there DTV compatibility planned for Chameleon?

No, unlikely to ever happen. The DTV started life as a C64 emulator. So then we are emulating an emulator (not a real good one either). Not all the quirks of the DTV are yet known and documented. Also it neither has a true 6510 cpu emulation nor is it 65816 like. So that would require designing a complete new processor based on reversed engineerd DTV specs.

If the 6510 CPU is emulated, can the tape still work? Can the original CPU work next to the emulated one?

No, the tape drive is inoperable when the Chameleon is used. The 6510-chip in the C64 is completely switched off. Although technically it is possible to run both CPUs at the same time, there is no software support yet that makes this possible.

What is stand-alone mode and does the cartridge needs external power?

When the cartridge is plugged in the expansion port it will gets its power from the C64 computer. There is no need for an external power source as the cartridge uses very little power. The cartridge can also function stand-alone. In this case the cartridge does need an external source (5 volt through USB cable). When it detects that it is not plugged in, the catridge will switch on some additional emulation blocks. The result is a C64 hardware emulator with all the Chameleon features in the small form factor of a C64 cartridge.

Is the VGA reprogrammable for more colors or higher resolutions?

Yes, Chameleon supports upto 8 bit/pixel color-depth (256 different colors arranged as 1 byte/pixel) and screen resolutions upto 1024x768. The VGA controller supports multiple layers of bitmaps of different resolution, sizes and color-depth. Each object can be positioned freely on the screen and supports smooth-scroll in all 4 directions. Each object can have a transparent color (index 0) so they can function as sprites (MOBs) too. There are a total of 256 slots to put objects in. The size and total number of objects that can actually be displayed at the same time is limited by the memory bandwidth.

Is dual monitor supported (C64 video port and VGA showing a different picture)?

The hardware can do this and the required register settings will be documented, but there is at the moment no software that supports this mode.

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