The structure of G-VRAM differs depending on the actual screen size and the number of colors. A total of 512 KB of VRAM is divided and allocated.
The pixel representation is a linear type and in any mode one pixel is represented by one word. In the 16/256 color display mode only the lower 4/8 bits are effective.
X = X coordinate in normal mode Y = Y 〃 P = Plane number ADR = 65536 color display mode address (X,Y) BIT = 〃 bit position
Real screen 512×512 pixels、65536 color display
| Valid bits | Full 16 bits |
| 1 Row | 1024 bytes(512 words) |
| Page 0 | $c00000～$c7ffff |
Real screen 512×512 pixels、256 color display:
| Valid bits | Lower 8 bits |
| 1 Row | 1024 bytes(512 words) |
| Page 0 | $c00000～$c7ffff |
| Page 1 | $c80000～$cfffff |
ADR = $c00000＋Y×1024＋X×2 BIT = P×8 ～ P×8＋7 for 8 bits
Real screen 512×512 pixels、16 colors
| Valid bits | Lower 4 bits |
| 1 Row | 1024 bytes(512 words) |
| Page 0 | $c00000～$c7ffff |
| Page 1 | $c80000～$cfffff |
| Page 2 | $d00000～$d7ffff |
| Page 3 | $d80000～$dfffff |
ADR = $c00000＋Y×1024＋X×2 BIT = P×4 ～ P×4＋3 for 4 bits
Real screen 1024×1024 pixels、16 colors:
| Valid bits | Lower 4 bits |
| 1 Row | 2048 bytes(1024 words) |
| Page 0 | $c00000～$dfffff |
ADR = $c00000＋(Y＆511)×1024＋(X＆511)×2
BIT = (Y≧512)×8＋(X≧512)×4 ～
(Y≧512)×8＋(X≧512)×4＋3 for 4 bits
T-VRAM has a real screen size of 1024×1024 pixels fixed to 16 color display and 4 planes for a total of 512KB. Pixel representation is planar type, 1 word is 16 horizontal pixels. Each plane represents 1 bit of the 4-bit palette code.
| 1 Row | 128 bytes(64 words) |
| Page 0 | $e00000～$e1ffff |
| Page 1 | $e20000～$e3ffff |
| Page 2 | $e40000～$e5ffff |
| Page 3 | $e60000～$e7ffff |