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6 . 9
Q2 Internal Buffers
The Q2 has three internal buffers—a command buffer, source buffer, and work buffer—as shown in
figure 6-5.
Address
16 × (n + 1)
Display list
16 × (n + 2)
Address
Binary source
coordinates
or
16 × (k + 1)
multi-valued
source
16 × (k + 2)
coordinates
Address
Binary work
4 × (p + 1)
coordinates
4 × (p + 2)
Note: n, k, and p are natural numbers.
Figure 6-5
These buffers are used by the Q2 to temporarily store data held in the UGM. The Q2 uses the data
stored in these buffers when executing drawing.
The functions of these buffers are shown in (a) to (c) below.
(a) Command buffer: Used by the Q2 to store a display list held in the UGM
(b) Source buffer: Used by the Q2 to store a binary source or multi-valued source held in the UGM
(c) Work buffer: Used by the Q2 when performing drawing at binary work coordinates in the UGM
The size of these buffers is fixed: 16 words each for the command buffer and source buffer, and 4
words for the work buffer.
168
UGM
16 × n
A
B
16 × k
C
D
4 × p
E
F
Updating of Q2's Internal Buffers
Q2
Command buffer
A → B
Size: 16 words
Source buffer
C → D
Size: 16 words
Work buffer
E → F
Size: 4 words
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