Yamaha V9938

The Yamaha V9938 is a video display processor (VDP) used on the MSX2 home computer, as well as on the Geneve 9640 enhanced TI-99/4A clone and the Tatung Einstein 256. It was also used in a few MSX1 computers, in a configuration with 16kB VRAM.

Yamaha V9938 in an MSX2

The Yamaha V9938, also known as MSX-Video or VDP (Video Display Processor), is the successor of the Texas Instruments TMS9918 used in the MSX1 and other systems. The V9938 was in turn succeeded by the Yamaha V9958.

Specifications

• Video RAM: 16–192 KB
• Text modes: 80 × 24, 40 × 24 and 32 × 24
• Resolution: 512 × 212 (16 colors from 512), 256 × 212 (16 colors from 512) and 256 × 212 (256 colors)
• Sprites: 32, 16 colors, max 8 per horizontal line
• Hardware acceleration for copy, line, fill and logical operations available
• Interlacing to double vertical resolution
• Vertical scroll register

Detailed specifications

• Video RAM: 4 possible configurations
  • 16 KB (modes G4 up to G7 will not be available)
  • 64 KB (modes G6 and G7 will not be available)
  • 128 KB: most common configuration
  • 192 KB, where 64 KB is extended-VRAM (only available as back-buffer for G4 and G5 modes)
• Clock: 21 MHz
• Video output frequency: 15 kHz
• Color encoding: Software switchable between 50 Hz PAL mode and 60 Hz NTSC mode
• Sprites: 32, 16 colors (1 per line. 3, 7 or 15 colors/line by using the CC attribute), max 8 per horizontal line
• Hardware acceleration, with copy, line, fill etc. With or without logical operations.
• Vertical scroll register
• Capable of superimposition and digitization
• Support for connecting a lightpen and a mouse
• Resolution:
  • Horizontal: 256 or 512
  • Vertical: 192p, 212p, 384i or 424i
• Color modes:
  • Paletted RGB: 16 colors out of 512 (9-bit RGB)
  • Fixed RGB: 256 colors
• Screen modes
  • Text modes:
    • T1: 40 × 24 with 2 colors (out of 512)
    • T2: 80 × 24 with 4 colors (out of 512)
    • All text modes can have 26.5 rows as well.
  • Pattern modes
    • G1: 256 × 192 with 16 paletted colors and 1 table of 8×8 patterns
    • G2: 256 × 192 with 16 paletted colors and 3 tables of 8×8 patterns
    • G3: 256 × 192 with 16 paletted colors and 3 tables of 8×8 patterns
    • MC: 64 × 48 with 16 paletted colors and 8×2 patterns
    • All modes with 192 lines can have 212 lines as well (similarly 48 → 53 in MC)
  • Bitmap modes:
    • G4: 256 × 212 with 16 paletted colors
    • G5: 512 × 212 with 4 paletted colors
    • G6: 512 × 212 with 16 paletted colors
    • G7: 256 × 212 with 256 fixed-colors
    • All modes with 212 lines can have 192 lines as well (similarly 48 → 53 in MC)
    • All vertical resolutions can be doubled by interlacing

MSX-specific terminology

On MSX, the screen modes are often referred to by their assigned number in MSX-Basic. This mapping is as follows:

Basic mode	VDP mode	MSX system
Screen 0 (width 40)	T1	MSX 1
Screen 0 (width 80)	T2	MSX 2
Screen 1	G1	MSX 1
Screen 2	G2	MSX 1
Screen 3	MC	MSX 1
Screen 4	G3	MSX 2
Screen 5	G4	MSX 2
Screen 6	G5	MSX 2
Screen 7	G6	MSX 2
Screen 8	G7	MSX 2

See also

• Texas Instruments TMS9918
• Yamaha V9958

External links

MSX-Video Technical Data Book, for Yamaha V9938 (August 1985) bitsavers.org

V9938 programmer guide http://rs.gr8bit.ru/Documentation/V9938-programmers-guide.pdf