VT8601 Via, VT8601 Datasheet - Page 83

• Manufacturer Part Number: VT8601
• Description: Slot-1 / Socket-370 PCI North Bridge
• Manufacturer: Via

Graphics Clock Synthesizer Control
SR18 – VCLK1 Frequency Control 0 .............................. RW
SR19 – VCLK1 Frequency Control 1 .............................. RW
SR1A – VCLK2 Frequency Control 0 ............................. RW
SR1B – VCLK2 Frequency Control 1 ............................. RW
Revision 1.3 September 8, 1999
7-0
7-6
5-0
7-0
7-6
5-0
7HFKQRORJLHV ,QF
VCLK1 Frequency Generator Numerator .... def=0
VCLK1 Frequency Generator K-Factor ....... def=0
VCLK1 Frequency Generator Denominator. def=0
VCLK2 Frequency Generator Numerator .... def=0
VCLK2 Frequency Generator K-Factor ....... def=0
VCLK2 Frequency Generator Denominator. def=0
:H &
:H &R R QQHFW
The clock frequency can be derived by multiplying the reference frequency times (N+8) / [(M+2) x 2
QQHFW
Denominator
Value
4A
88
89
88
83
85
84
84
84
43
46
42
43
43
48
46
44
44
42
44
44
44
44
44
04
07
02
03
05
05
05
Table 8. Graphics Clock Frequencies – 14.31818 MHz Reference
Numerator
Value
5A
5D
4A
1B
3B
4A
3C
3A
4B
3E
4F
30
42
43
48
33
18
21
23
63
53
43
33
34
22
39
42
44
22
19
22
90
62
79
93
48
74
66
67
72
27
51
24
33
35
99
83
67
51
52
34
57
59
66
68
74
34
60
25
34
58
75
N
M
10
8
9
8
3
5
4
4
4
3
6
2
3
3
8
6
4
4
2
4
4
4
4
4
4
7
2
3
5
5
5
-77
K
0
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
SR20 – Clock Synthesizer / RAMDAC Setup ................. RW
1-0
7
6
5
4
3
2
Frequency
200.455
100.227
108.182
118.125
120.273
135.000
169.773
Actual
25.057
28.311
36.153
40.091
41.932
44.148
44.744
47.727
50.114
52.798
57.273
58.705
61.568
63.835
65.148
67.116
70.398
71.591
75.170
77.557
79.943
88.295
90.682
97.841
Reserved
Multiplex Mode Sync Mechanism
Simultaneous VAFC and Playback
VAFC and Playback Display Overlay
DAC Test Mode
Video Mode
Video Mode Select
x0 5-5-5 Hi-color ..................................default = 0
x1 5-6-5 XGA-color
0x Video Playback, True-color
1x Video Playback, 256-color
0
1
0
1
0
1
0
1
0
1
Normal Mode......................................... default
Enable synchronization in multiplexed mode
for high VCLK tracking
Simultaneous VAFC / playback display default
Playback only
VAFC is on top...................................... default
Playback is on top
Disable................................................... default
Enable
Disable................................................... default
Enable
Frequency
Expected
200.000
100.000
108.000
118.000
120.000
135.000
170.000
25.175
28.322
36.000
40.000
42.000
44.000
44.900
48.000
50.350
52.800
57.270
58.800
61.600
64.000
65.000
67.200
70.400
72.000
75.000
77.000
80.000
88.000
90.000
98.000
........................................always reads 0
VT8601 Apollo ProMedia
Frequency
Error %
VGA Extended Registers
-0.0047
-0.0004
-0.0016
-0.0035
-0.0057
-0.0047
-0.0016
-0.0005
-0.0026
-0.0012
-0.0057
-0.0007
-0.0016
-0.0013
0.0023
0.0043
0.0023
0.0034
0.0000
0.0000
0.0023
0.0000
0.0023
0.0072
0.0034
0.0076
0.0023
0.0017
0.0011
0.0023
0.0000
K
]