The Yamaha V9938 VDP

Early Rev A model

Description

The Yamaha V9938 is a Video Display Processor (VDP) used in most MSX2 computers. It is the successor of the Texas Instruments TMS9918 used in the MSX1 and various other systems. The V9938 was succeeded by the Yamaha V9958.

A few MSX1 computers have also this VDP without the corresponding VRAM, but the MSX2 screen modes are normally not accessible, as they require more than 16kB VRAM. See the list below.

Specifications

• VRAM: 64 kB, 128 kB or 192 kB
• Text modes: 80 x 24, 40 x 24 and 32 x 24
• Resolution: 512 x 212 (4 or 16 colors from 512) , 256 x 212 (16 colors from 512) and 256 x 212 (256 colors)
• Sprites: 32, 16 colors, 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

• VRAM: 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 colors (1 color per line), maximum 8 per horizontal line
• Hardware acceleration, with copy, line, fill etc. (logical operations possible)
• 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)
• Color modes:
  • Paletted RGB: 16 colors out of 512
  • Fixed RGB: 256 colors
• Screen modes
  • Text modes:
    • T1: 40 × 24 with 2 colors (out of 512)
    • T2: 80 × 24 with 4 colors (out of 512)
    • All text modes can have 26.5 rows as well.
  • Pattern modes
    • G1: 256 × 192 with 16 paletted colors and 1 tables of 8×8 patterns
    • G2: 256 × 192 with 16 paletted colors and 3 table of 8×8 patterns
    • G3: 256 × 192 with 16 paletted colors and 3 tables of 8×8 patterns
    • MC: 64 × 48 with 16 paletted colors and 8×2 patterns
    • All modes with 192 lines can have 212 lines as well.
  • Bitmap modes:
    • G4: 256 × 212 with 16 paletted colors
    • G5: 512 × 212 with 4 paletted colors
    • G6: 512 × 212 with 16 paletted colors
    • G7: 256 × 212 with 256 fixed-colors
    • All modes with 212 lines can have 192 lines as well (similarly 48 ? 53 in MC).
    • All vertical resolutions can be doubled by interlacing
• Packaging: 64 pin "Shrink" DIP (SDIP) or Ceramic DIP (CDIP)

Variants

A few variants exist. The first variation is the foundry where Yamaha had the chips produced. Chips with the markings 2302 were manufactured by Sharp, while those with 2701 were manufactured by Hitachi.

The second variant, is the revision. Early revisions have no additional letter, and are effectively A revisions. Later revisions are marked either B or C. The difference between these revisions is documented in the V9938 Technical Data Book. Page 134 shows how to identify revisions. Page 124 show how version A and B have different timing towards VRAM. Page 126 shows differences in video output level for revision C compared to A and B.

Known variations

MSX1 computers with MSX2 VDP

A few MSX1 machines have the MSX2 VDP (V9938). The MSX2 screen modes are normally not accessible, as they require more than 16kB VRAM.

• Sakhr AX-200
• Sakhr AX-330 (2nd version)
• Spectravideo SVI-738
• Talent DPC-200A
• Yamaha CX11
• Yamaha CX5MII - note: this computer has an extra ROM allowing to use 80 columns in screen 0
• Yamaha YIS-503II
• Yamaha YIS-503IIR
• Yamaha YIS-603

MSX screens

On MSX, the documented screen modes are often referred to by their assigned number in MSX-BASIC (see SCREEN page for more info). This mapping is as follows:

Links

• V9938 Programmer's guide
• V9938 Technical Data Book