Yamaha V9958

Yamaha V9958

Yamaha V9958 in ceramic package

The Yamaha V9958 ^{[1] [2] [3]} is a Video Display Processor used in the MSX2+ ^[4] and MSX turbo R series of home computers, as the successor to the Yamaha V9938 used in the MSX2, as well as the "TI Image Maker" video expansion for the TI-99/4A home computer. ^[5] The main new features are three graphical YJK ^{[6] [7] [8]} modes with up to 19268 colors and horizontal scrolling registers. The V9958 was not as widely adopted as the V9938.

Specifications

• Video RAM: 128 KB + 64 KB of expanded VRAM
• Text modes: 80 × 24 and 32 × 24
• Resolution: 512 × 212 (4 or 16 colors out of 512) and 256 × 212 (16, 256, 12499 or 19268 colors)
• Sprites: 32, 16 colors, max 8 per horizontal line
• Hardware acceleration for copy, line, fill, etc.
• Interlacing to double vertical resolution
• Horizontal and vertical scroll registers

Feature changes from the V9938

The following features were added to or removed from the Yamaha V9938 specifications:

• Added horizontal scrolling registers
• Added YJK graphics modes (similar to YUV):
  • G7 + YJK + YAE: 256 x 212, 12499 colors + 16 color palette
  • G7 + YJK: 256 × 212, 19268 colors
• Added the ability to execute hardware accelerated commands in non-bitmap screen modes
• Removed lightpen and mouse functions
• Removed composite video output function

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
Screen 10	G7 with YJK and YAE	MSX 2+ and tR
Screen 11	G7 with YJK and YAE	MSX 2+ and tR
Screen 12	G7 with YJK	MSX 2+ and tR

References

1. IC Master. United Technical Publications. 2001.
2. Martín Sesma, Sergio (2016-10-03). Arqueología informática: los ordenadores MSX en los inicios de la microinformática doméstica (Proyecto/Trabajo fin de carrera/grado thesis). Universitat Politècnica de València.
3. Redazione (2008-10-20). "MSX - Vari Costruttori- 1983". CyberLudus.com (in Italian). Retrieved 2022-11-13.
4. Alex, Wulms (1995). "Schermen op MSX - De 2+ schermen" (PDF). MSX Computer & Club Magazine (72).
5. "TI Image Maker – Gary O . P . A " . Retrieved 2025-06-30.
6. MSX Licensing Corporation (2022). "The YJK screen modes". MSX Assembly Page.
7. Niemietz, Ricardo Cancho (2014). Issues on YJK colour model implemented in Yamaha V9958 VDP chip (PDF).
8. "VCFe Vortrag vom 2016.04.30 - Homecomputer und Spielkonsolen - Videoarchitekturen als visuelles Medium". neil.franklin.ch. Retrieved 2022-11-13.