MOS Technology VIC-II
The VIC-II (Video Interface Chip II), specifically known as the MOS Technology 6567/8562/8564 (NTSC versions), 6569/8565/8566 (PAL), is the integrated circuit chip tasked with generating composite video graphics and DRAM refresh signals in the Commodore 64 and C128 home computers.Succeeding MOS' original VIC (used in the VIC-20), the VIC-II was one of the two chips mainly responsible for the C64's success as the best-selling computer model of all time (the other chip being the 6581 SID). One of the engineers working on the VIC-II was SID chip designer Robert Yannes.
An improved version of VIC-II, VIC-III codenamed Bill, appeared in the Commodore 65 prototype but was never used.
The VIC-II was programmed by manipulating its 47 control registers (up from 16 in the VIC), memory mapped to the range $D000–$D02E in the C64 address space. Of all these registers, 34 dealt exclusively with sprite control (sprites being called MOBs, from Movable Object Blocks, in the VIC-II documentation). Like its predecessor, the VIC-II handled light pen input, and, with help from the C64s standard character ROM, provided the original PETSCII character set from 1977 on a similarly dimensioned display as the 40 column PET series, allowing some degree of PET BASIC program emulation on the C64.
By reloading the VIC-II's control registers via machine code hooked into the raster interrupt routine (the scanline interrupt), one could program the chip to generate significantly more than 8 concurrent sprites (a process known as sprite multiplexing), and generally give every program-defined slice of the screen different scrolling, resolution and color properties. The hardware limitation of 8 sprites per scanline could be increased further by letting the sprites flicker rapidly on and off. Mastery of the raster interrupt was essential in order to unleash the VIC-II's capabilities.
The 8564/8566 VIC-II in the Commodore 128 had two extra registers, one for accessing the numerical keypad and some extra keys, and the other for toggling between a 1 MHz and a 2 MHz system clock; at the higher speed the VIC-II's composite video output was disabled, suggesting use of the C128's 80-column mode at that speed (via the 8563 VDC RGB chip). Rather unofficially, the two extra registers were also available in the C128's C64 mode, permitting some use of the extra keys, as well as double-speed-no-video execution of CPU-bound code (i.e. numerical calculations) in self made C64 programs.
VIC-II features
Technical details
VIC-II ICs
References
External links