CPU Temperature Shenanigans - Printable Version

Code:
#Temperature Read code crap, works on Dolphin when you simulate fake THRM register bit responses on the read-only bits

#Wont work on Wii, intended for GC, not tested on real hardware



#SPR list

#1020 = THRM1

#1021 = THRM2

#1022 = THRM3 (the TAU aka Thermal Assist Unit)



#TAU is currently running, disable it. Clear any previous data.

li r0, 0

mtspr 1022, r0



#We want to use TAU in single mode, disable usage of THRM2

#Clear the V (SPR valid) bit; bit 31

#I might be able to just write null to the register to disable it, but it may cause a program exception due to possibly writing new values to the read-only bits. Play it safe.

mfspr r0, 1021

rlwinm r0, r0, 0, 0, 30

mtspr 1021, r0



#Prepare THRM1

#Enable it (V high)

#Disable Thermal Interrupts (TIE low)

#Set initial threshold of 0x40 degress celisus (bits 2 thru 8)

#Clear TID bit so when TIN is high, we know above threshold, and when TIN is low we below it

mfspr r0, 1020

andis. r0, r0, 0xC000 #Clear everything out but the read-only bits

oris r0, r0, 0x2000 #Bits 2 thru 8 are set to value of 0x40

ori r0, r0, 0x0001 #Flip V (spr valid) bit high

mtspr 1020, r0



#Prepare THRM3

#Enable it (E bit high)

#Don't have any calibration set

#Set timer cycles to max (0x1FFF); the more cycles, the more accurate the reading; bits 18 thru 30 all high

li r0, 0x3FFF



#Start the TAU!

mtspr 1022, r0



#The most you can poll is 5 times, due to temperature readings being in 4*C increments. Poll 5 times for the highest accuracy.

#Set loop to 5

li r0, 5

mtctr r0



#Set initial threshold increment/decrement value (0x20)

li r5, 0x40 #Will be halved before first iteration, hence why we first set it to 0x40



#Temperature Check Loop

loop:



#Read THRM1 

mfspr r3, 1020



#Temp is above threshold when following bits are this.. (combo only correct when TID is set to 0)

#TIN = 1

#TIV = 1



#Temp is below threshold when bits are this (only correct when TID is set to 0)

#TIN = 0

#TIV = 1



#Check if TIV is high (valid) 

#This tells temperature has crossed the threshold

andis. r0, r3, 0x4000

beq- loop



#Temperature has crossed threshold, figure out if it crossed above or below (check TIN bit)

andis. r0, r3, 0x8000



#Extract the threshold from THRM1 and right align it, divide r5 by 2, adjust current threshold by new amount in r5

rlwinm r4, r3, 9, 25, 31

srwi r5, r5, 1 



#Now branch

beq- lower_threshold



#Temperature is above threshold; raise it

add r0, r4, r5

b decrement_loop



#Temperature is below threshold; lower it

lower_threshold:

subf r0, r5, r4 #Equivalent to sub r0, r4, r5



#Place in new threshold value, update THRM1, decrement Loop

decrement_loop:

rlwimi r3, r0, 23, 2, 8 #Shift r0's value (new threshold) to be in bits 2 thru 8; then replace those bits into r3 while leaving all other r3's bits alone

mtspr 1020, r3

bdnz+ loop



#Loop is over, place latest iteration of r4 as the result; is this even accurate, lol?

mr r3, r4