Here is some details about the patch (BIOS version 1CCN26WW).
First of all temperature tables, in Celsius (BIOS file offset 0x9BAC):
1)
50 - 45
57 - 50
65 - 55
73 - 65
85 - 75
2)
50 - 45
57 - 50
65 - 55
73 - 65
80 - 70
3)
44 - 40
49 - 45
52 - 47
54 - 49
64 - 55
4)
60 - 55
60 - 55
60 - 55
70 - 60
76 - 65
5)
70 - 60
70 - 60
70 - 60
80 - 65
95 - 80
6)
00 - 10
55 - 50
60 - 55
65 - 60
70 - 65
7)
68 - 65
68 - 65
82 - 46
86 - 75
90 - 80
Each table is divided on 5 intervals. The first number in each interval is the upper limit, the second one is the lower limit.
When temperature intersects the upper limit, we automatically move into the next interval. When temperature intersects the lower limit, we go down into the previous interval. Fan speed is changed only when temperature intersects any limit, while temperature is within interval - fan speed is not changed.
Now about two fan speeds tables (BIOS file offsets 0x9C66 and 0x9C7E)
1)
FFFF
02CE
028D
0246
020E
01EA
2)
FFFF
01D5
019F
017A
015C
0138
Each table contains 6 speeds. Fan speed is driven by PWM (Pulse Width Modulation). The first byte of speed value is PWM base frequency divider, the second one denotes the duration of zero level in PWM impulse (0x00 - duty cycle is 100%, 0xFF - duty cycle is 0%). Lets take two values for example:
FFFF - the fan is completely OFF;
02CE - the base PWM frequency is divided by 2, duty cycle = 100% - 100% * (0xCE / 0xFF) = 19%.
So how does all this stuff work? Assume that U350 firmware uses the first temperature table and the second fan speeds table. In that case we have the following correspondence between temperatures and fan speeds:
50 (01D5) - 45 (FFFF)
57 (019F) - 50 (01D5)
65 (017A) - 55 (019F)
73 (015C) - 65 (017A)
85 (0138) - 75 (015C)
And finally what I did in the latest version of the patch. I changed two fan speeds tables:
1)
04E0
04E0
04E0
04E0
04E0
01EA
2)
04E0
04E0
04E0
04E0
04E0
0138
According to testers, the fan rotates at almost inaudible speed all the time and turns on full throttle only if CPU temperature is above 55-60 degrees in Celsius.
I hope using this information you can tune up the fan the way you want (if my patch doesn't suit you).
