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Yamaha V9938 in a MSX 2

The Yamaha V9938 is a Video Display Controller (VDC) used in the Geneve 9640 enhanced TI-99/4A clone, as well as MSX 80s home computers (more specifically, the MSX 2).

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: 64 KB to 128 KB
  • Text modes: 80 x 24, 40 x 24 and 32 x 24
  • Resolution: 512 x 212 (4 colours from 512) , 256 x 212 (16 colours from 512) and 256 x 212 (256 colours)
  • Sprites: 32, 16 colours, max 8 per horizontal line
  • Hardware acceleration for copy, line, fill, etc. Logical operations available.
  • Interlacing to double vertical resolution
  • Vertical scroll register

Detailed specifications

  • Video RAM: 128 kB
    • Optionally 64 kB, in which case screen modes G6 and G7 are not available
    • Optionally 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), 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: 192, 212, 384 (interlaced) or 424 (interlaced)
  • 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 tables of 8×8 patterns
      • G2: 256 × 192 with 16 paletted colours and 3 table 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







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