MOS Technology 8563
MOS Technology 8563 Video Display Controller (VDC) - MOS Technology integrated circuit. It was used on Commodore 128 to display an 80-column image at a resolution of 640 × 200.
The original was intended for a Unix computer that was not originally intended. Commodore installed it only in a few prototype copies of the machine. Unlike previous MOS video chips such as the VIC-II, the VDC had 16 KB of VRAM (expandable to 64 KB). This memory was not directly available to the processor. Initially, the product was not profitable and the production process was a bit more difficult compared to the rest of the MOS product range. Text editor displayed by VDC
Officially, the 8563 was capable of displaying only text, although a careful reading of the technical specifications resulted in the existence of a high resolution graphic mode. Commodore BASIC 7.0 built into C128 only supports 40-column high-resolution mode, via the VIC-II. Shortly after the launch of C128, the high-resolution graphic mode was thoroughly described in the Data Becker book published at the end of 1985. Along with the publication was provided a program to enable each pixel on the screen from the BASIC language. It also enabled the drawing of geometric shapes in 80-column graphic mode. In February 1986 RUN magazine published an article titled Ultra Hi-Res Graphics, which also describes this mode. The included program listing (in machine language) extended BASIC's ability to support 640 × 200 resolution using the 8563 system. Later, the authors, Lou Wallace and David Darus, released the Ultra Hi-Res program for BASIC 8.0. Finally, Commodore decided to publish the official VDC documentation. Commodore 128 Programmer's Guide. Graphical mode was used extensively by the GEOS operating system. Although VDC did not support sprite objects, it had the ability to copy Blocks directly to VRAM.
When addressing the internal MOS 8563 registers, the program had to know which 37 registers to access. Then the program had to wait for the system to be ready and allow access. The operation is as follows: ldx #regnum ;VDC register to access stx $d600 ;write to control register loop bit $d600 ;check bit 7 of status register bpl loop ;VDC not ready lda $d601 ;get contents of VDC register
The maximum number of frames per second you can get in graphical mode thanks to this VDC control method was too small to meet the demands of the game. Technical data
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