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2-3 Timing Chart
This section of the service manual describes the timing that the computer industry recognizes as standard
for computer-generated video signals.
Mode
VGA1/70 Hz
640 x 350
Timing
31.469
fH (kHz)
A µsec
31.778
3.813
B µsec
C µsec
1.589
26.058
D µsec
E µsec
0.318
70.086
fV (Hz)
O msec
14.268
0.064
P msec
Q msec
1.716
11.504
R msec
S msec
0.985
Clock
Frequency
25.175
(MHz)
Polarity
Positive
H.Sync
Negative
V.Sync
Separate
Remark
Separate Sync
Horizontal
Video
Video
C
D
E
C
D
E
Sync
Sync
Sync
B
B
A
A
A : Line time total
C : Back porch
E : Front porch
DS17BS*
Table 2-1 Timing Chart
IBM
VGA3/60 Hz
VGA2/70 Hz
640 x 480
720 x 400
31.469
31.469
31.777
31.778
3.813
3.813
1.589
1.589
26.058
26.058
0.318
0.318
70.087
59.940
14.268
16.683
0.064
0.064
0.858
0.794
13.155
15.761
0.191
0.064
28.322
25.175
Negative
Negative
Positive
Negative
Separate
Separate
Vertical
Video
Video
Q
R
S
Q
R
S
Sync
Sync
Sync
P
P
P
O
O
O
B : Horizontal sync width
D : Active time
VESA
640/72 Hz
640/75 Hz
640 x 480
640 x 480
37.861
37.500
26.413
26.667
1.270
2.032
3.810
3.810
20.825
20.317
0.508
0.508
72.809
75.000
13.735
13.333
0.079
0.080
0.528
0.427
13.100
12.800
0.026
0.027
31.500
31.500
Negative
Negative
Negative
Negative
Separate
Separate
H/V Composite Sync
A
Horizontal
Vertical
P
B
O : Frame time total
Q : Back porch
S : Front porch
2 Product Specifications
800/60 Hz
800/56 Hz
800 x 600
800 x 600
37.879
35.156
28.444
26.400
3.200
2.000
2.200
3.556
20.000
22.222
1.000
0.667
60.317
56.250
16.579
17.778
0.106
0.057
0.607
0.626
17.067
15.840
0.026
0.028
40.000
36.000
Positive
Positive
Negative
Positive
Separate
Separate
VIDEO
Q
S
R
O
P : Vertical sync width
R : Active time
2-3
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