Yamaha V9958 Explained
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. The main new features are three graphical YJK[5] [6] [7] 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 | |
Notes and References
- Book: IC Master . 2001 . United Technical Publications . en.
- Arqueología informática: los ordenadores MSX en los inicios de la microinformática doméstica . Universitat Politècnica de València . 2016-10-03 . Proyecto/Trabajo fin de carrera/grado . Sergio . Martín Sesma.
- Web site: Redazione . 2008-10-20 . MSX - Vari Costruttori- 1983 . 2022-11-13 . CyberLudus.com . it-IT.
- Alex . Wulms . 1995 . Schermen op MSX - De 2+ schermen . MSX Computer & Club Magazine . 72.
- Web site: MSX Licensing Corporation . 2022 . The YJK screen modes . MSX Assembly Page.
- Book: Niemietz, Ricardo Cancho . Issues on YJK colour model implemented in Yamaha V9958 VDP chip . 2014.
- Web site: VCFe Vortrag vom 2016.04.30 - Homecomputer und Spielkonsolen - Videoarchitekturen als visuelles Medium . 2022-11-13 . neil.franklin.ch.
