Yamaha V9938

Yamaha V9938 in an MSX2

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.

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 various 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 colours from 512), 256 × 212 (16 colours from 512) and 256 × 212 (256 colours)
Sprites: 32, 16 colours, 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 G6 and 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 backbuffer for G4 and G5 modes)
Clock: 21 MHz
Video output frequency: 15 kHz
Sprites: 32, 16 colours (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
Colour modes:
- Paletted RGB: 16 colours out of 512
- Fixed RGB: 256 colours
Screen modes
- Text modes:
  - T1: 40 × 24 with 2 colours (out of 512)
  - T2: 80 × 24 with 4 colours (out of 512)
  - All text modes can have 26.5 rows as well.
- Pattern modes
  - G1: 256 × 192 with 16 paletted colours and 1 table of 8×8 patterns
  - G2: 256 × 192 with 16 paletted colours and 3 tables of 8×8 patterns
  - G3: 256 × 192 with 16 paletted colours and 3 tables of 8×8 patterns
  - MC: 64 × 48 with 16 paletted colours 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 colours
  - G5: 512 × 212 with 4 paletted colours
  - G6: 512 × 212 with 16 paletted colours
  - G7: 256 × 212 with 256 fixed-colours
  - 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

External links

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

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