HP Vectra Technical Reference Manual page 39

Graphics Display Memory Organization
640 x 400 Graphics Display Memory
OB800:0H
OB800:2000H
OB800:4000H
OB800:6000H
Byte 0
I
Byte 1
I
Byte 2
I
• ••
I
Byte 79
•
•
•
Byte 0
I
Byte 1
I
Byte 2
I
• ••
I
Byte 79
•
•
•
Byte 0
I
Byte 1
I
Byte 2
I
• ••
I
Byte 79
·
•
•
Byte 0
I
Byte 1
I
Byte 2
I
• ••
I
Byte 79
•
•
•
Scan line
o
4
8
1
5
9
2
6
10
3
7
~
11
Byte I Pixel Organization
7 6 5 4 3 2 1 0 bit number
o
1 2 3 4 5 6 7 pixel number
o-
Background Color (Black)
1 - 1 of 16 Foreground Colors
Figure 3.3
In all the graphics modes, the memory used for scan lines is not sequential but it is interleaved at
fixed intervals of 8K. In the modes that are 200 scan lines, even scan lines start at offset 0 and
odd scan lines start at offset 2000H. In the modes that are 400 scan lines, the following table
can be used to determine the appropriate offset:
30 Video