I am now having questions about EG times. In "Inside X68000" there are two tables describing EG times (for a 4MHz clock), and in the YM2151 user manual there is one table describing the same things, but for a 3.579545MHz clock.
In the "Inside X68000" text, there is a formula:
Quote:
t = (10^4.202682)/(2^RATEH)*(1/(1+0.25*RATEL))*3.58/4.00
The last multiplication and division is obviously an adaptation from the "normal" YM2151 clock of 3.579545MHz rounded up to 3.58, to the 4MHz X68000 clock.
They also mention that the other values in the EG tables are just multiplied by a factor.
My questions are:
- Where is the value 4.202682 coming from, and why is it a power of 10? 10 ^ 4.202682 = 15947.110.
- For example, in the first table, dividing the 4th column by the second column gives a roughly constant 13.8219. Where does that come from?
- The next table divided by the second column in the first table gives ratios of roughly 0.56164 and 2.79452. Where do these come from?
Here is the jp text:
Quote:
EG の表の値はほぼ指数関数となっています。0~100%のアタック時間tは, RATEの上 位4ビットと下位2ビット(表の2番目, 3番目の数値)を使って計算されます。上位4ビッ トを RATEH, 下位2ビットを RATEL とすると,
t = (10^4.202682)/(2^RATEH)×(1/(1+0.25×RATEL))×3.58/4.00
で表されます。その他の時間は、この値にたんに係数をかけるだけで算出することができます。 OPMの時間の分解能の限界のために, tが小さくなってくると,この式で計算した値からずれ てしまいますので注意してください。
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Code:
●表......3 EG の各レート設定値と時間(0~100 %)
アタック ファーストディケイ/セカンド
ディケイ/リリース
AR×2+KS 時間(ms) XR×2+KS 時間(ms)
RR×4+2+KS
0: 0 0 無限大 0: 0 0 無限大
1: 0 1 恭限大 1: 0 1 無限大
2: 0 2 無限大 2: 0 2 無限大
3: 0 3 無限大 3: 0 3 無限大
4: 1 0 7136.33 4: 1 0 98637.69
5: 1 1 5709.06 5: 1 1 78910.15
6: 1 2 4757.55 6: 1 2 65758.46
7: 1 3 4077.90 7: 1 3 56364.40
8: 2 0 3568.16 8: 2 0 49318.84
9: 2 1 2854.53 9: 2 1 39455.07
10: 2 2 2378.78 10: 2 2 32879.23
11: 2 3 2038.95 11: 2 3 28182.20
12: 3 0 1784.08 12: 3 0 24659.42
13: 3 1 1427.27 13: 3 1 19727.54
14: 3 2 1189.38 14: 3 2 16439.61
15: 3 3 1019.48 15: 3 3 14091.09
16: 4 0 892.04 16: 4 0 12329.71
17: 4 1 713.63 17: 4 1 9863.77
18: 4 2 594.69 18: 4 2 8219.81
19: 4 3 509.74 19: 4 3 7045.55
20: 5 0 446.02 20: 5 0 6164.86
21: 5 1 356.82 21: 5 1 4931.89
22: 5 2 297.35 22: 5 2 4109.90
23: 5 3 254.87 23: 5 3 3522.77
24: 6 0 223.01 24: 6 0 3082.42
25: 6 1 178.41 25: 6 1 2465.94
26: 6 2 148.68 26: 6 2 2054.95
27: 6 3 127.43 27: 6 3 1761.38
28: 7 0 111.51 28: 7 0 1541.22
29: 7 1 89.20 29: 7 1 1232.97
30: 7 2 74.34 30: 7 2 1027.48
31: 7 3 63.72 31: 7 3 880.59
32: 8 0 55.75 32: 8 0 770.60
33: 8 1 44.60 33: 8 1 616.48
34: 8 2 37.16 34: 8 2 513.74
35: 8 3 31.86 35: 8 3 440.35
36: 9 0 27.88 36: 9 0 385.31
37: 9 1 22.30 37: 9 1 308.25
38: 9 2 18.58 38: 9 2 256.83
39: 9 3 15.93 39: 9 3 220.17
40: 10 0 13.94 40: 10 0 192.65
41: 10 1 11.15 41: 10 1 154.12
42: 10 2 9.29 42: 10 2 128.43
43: 10 3 7.97 43: 10 3 110.09
44: 11 0 6.97 44: 11 0 96.33
45: 11 1 5.58 45: 11 1 77.06
46: 11 2 4.65 46: 11 2 64.22
47: 11 3 3.98 47: 11 3 55.04
48: 12 0 3.48 48: 12 0 48.16
49: 12 1 2.78 49: 12 1 38.53
50: 12 2 2.33 50: 12 2 32.11
51: 12 3 1.99 51: 12 3 27.52
52: 13 0 1.91 52: 13 0 24.08
53: 13 1 1.53 53: 13 1 19.27
54: 13 2 1.27 54: 13 2 16.06
55: 13 3 1.09 55: 13 3 13.77
56: 14 0 1.00 56: 14 0 12.04
57: 14 1 0.81 57: 14 1 9.63
58: 14 2 0.67 58: 14 2 8.03
59: 14 3 0.57 59: 14 3 6.88
60: 15 0 0.47 60: 15 0 6.02
61: 15 1 0.47 61: 15 1 6.02
62: 15 2 0.47 62: 15 2 6.02
63: 15 3 0.00 63: 15 3 6.02
Code:
●表.........4 EG D各一下設定值時間(10~90%)
アタック ファーストディケイ/セカンド
ディケイ/リリース
AR×2+KS 時間(ms) XR×2+KS 時間(ms)
RR×4+2+KS
0: 0 0 無限大 0: 0 0 無限大
1: 0 1 無限大 1: 0 1 無限大
2: 0 2 無限大 2: 0 2 無限大
3: 0 3 無限大 3: 0 3 無限大
4: 1 0 4008.07 4: 1 0 19942.60
5: 1 1 3206.45 5: 1 1 15954.08
6: 1 2 2672.05 6: 1 2 13295.07
7: 1 3 2290.32 7: 1 3 11395.78
8: 2 0 2004.04 8: 2 0 9971.30
9: 2 1 1603.23 9: 2 1 7977.05
10: 2 2 1336.02 10: 2 2 6647.53
11: 2 3 1145.16 11: 2 3 5697.88
12: 3 0 1002.02 12: 3 0 4985.65
13: 3 1 801.62 13: 3 1 3988.52
14: 3 2 668.01 14: 3 2 3323.77
15: 3 3 572.59 15: 3 3 2848.95
16: 4 0 501.01 16: 4 0 2492.83
17: 4 1 400.81 17: 4 1 1994.26
18: 4 2 334.01 18: 4 2 1661.88
19: 4 3 286.29 19: 4 3 1424.47
20: 5 0 250.50 20: 5 0 1246.41
21: 5 1 200.40 21: 5 1 997.13
22: 5 2 167.01 22: 5 2 830.94
23: 5 3 143.15 23: 5 3 712.23
24: 6 0 125.26 24: 6 0 623.21
25: 6 1 100.20 25: 6 1 498.57
26: 6 2 83.50 26: 6 2 415.47
27: 6 3 71.57 27: 6 3 356.12
28: 7 0 62.62 28: 7 0 311.60
29: 7 1 50.10 29: 7 1 249.28
30: 7 2 41.75 30: 7 2 207.74
31: 7 3 35.78 31: 7 3 178.04
32: 8 0 31.32 32: 8 0 155.80
33: 8 1 25.05 33: 8 1 124.64
34: 8 2 20.87 34: 8 2 103.86
35: 8 3 17.89 35: 8 3 89.03
36: 9 0 15.65 36: 9 0 77.90
37: 9 1 12.52 37: 9 1 62.32
38: 9 2 10.44 38: 9 2 52.83
39: 9 3 8.95 39: 9 3 44.52
40: 10 0 7.83 40: 10 0 38.95
41: 10 1 6.27 41: 10 1 31.16
42: 10 2 5.22 42: 10 2 25.96
43: 10 3 4.48 43: 10 3 22.26
44: 11 0 3.91 44: 11 0 19.48
45: 11 1 3.13 45: 11 1 15.58
46: 11 2 2.61 46: 11 2 12.98
47: 11 3 2.24 47: 11 3 11.12
48: 12 0 1.96 48: 12 0 9.74
49: 12 1 1.57 49: 12 1 7.79
50: 12 2 1.31 50: 12 2 6.49
51: 12 3 1.12 51: 12 3 5.57
52: 13 0 0.98 52: 13 0 4.87
53: 13 1 0.78 53: 13 1 3.89
54: 13 2 0.65 54: 13 2 3.26
55: 13 3 0.55 55: 13 3 2.78
56: 14 0 0.52 56: 14 0 2.43
57: 14 1 0.42 57: 14 1 1.95
58: 14 2 0.36 58: 14 2 1.62
59: 14 3 0.30 59: 14 3 1.39
60: 15 0 0.24 60: 15 0 1.22
61: 15 1 0.24 61: 15 1 1.22
62: 15 2 0.24 62: 15 2 1.22
63: 15 3 0.00 63: 15 3 1.22
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