Yamaha V9938

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Yamaha V9938 in a MSX 2

The Yamaha V9938 was 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, is the successor of the Texas Instruments TMS9918 (used in the MSX1). 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: 21MHz
• Video output frequency: 15kHz
• 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
• 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: