[Xperia Z General] Haldi4803:
How to Overclock/Undervolt the Sony Xperia Z with Doomkernel (v09)

Disclaimer: This might Damage your phone! Do it on your own Risk

Things you Need:

Doomkernel v09 (or any other Kernel that Supports Overclocking / Voltage Control

Apps for Controling CPU:

My choice of Apps:

Kernel Tuner: Is needed because ATM its the only app that can keep 4 Cores awake/active: But Warning! Make sure to disable "Restore Settings After Reboot" in the General Settings of the App!

Incredicontrol: my favorite app for Voltage control! But you could also use Kernel Tuner (only down to 700mv) or Faux Kernel app, or trickster

No Frills CPU control: My favorite CPU control app, because you can select CPU speed from a dropdown menue and don't need to aim with a slider! Any other CPU Control app will do !

AnTuTu Benchmark: Mainly for the Stress Test, and because it increases CPU speed to maximum when running.

Qualcomm Trepn Profiler: Graphical Overlay that shows CPU/ GPU Frequency, good for checking throttling/ core activity.

Overclocking and Undervolting, basically the same:

It doesn't really matter if you want to overclock or undervolt, you want a certain frequency stable and need a specific Voltage to get it running!

But be aware! Running doesn't mean stable! I had to realize this when i ran 702mhz with 725mV, seemed all to work, except when i tried to take a Screenshot. (Picture below) increasing Voltage to 750mV and the Problem is gone!

How do i realize it is stable ?

If it's not crashing it seems stable!

i prefer the hard way of aproaching, decrease Voltage as long as the phone does not crash.

There are some other tricks to see if the phone is stable or not:

DO not use Performance governor

If you run Antutu Stress test or Performance Governor your phone might seem stable! But the qualcomm SoC mostly crash when changing frequencys and not when running under full load! Thats why i dislike Performance Governor, just quit Antutu and you can see the CPU speed dropping, if it is still stable then it will most likely run.

Try taking a Screenshot! Especially on Low frequncys if you don't have enough Voltage Screenshots will have graphical errors.

DO not limit Lower Frequencys, because that would have a similar effect as Performance governor.

Increase the heat of the CPU: Especially on high frequency. The hotter the CPU the more instable it becomes. If you run around 65-70°C (thats around when it starts throttling) This is especially important on lower frequencys! if you set 192mhz on 625mV that might seem stable at this frequency only, but when you play a game and have 70°C Core Temp, and then core goes into low power stat of 192mhz it might crash

Connecting USB cable and Charge the phone! This results in a way hotter SoC and also results in crash if its not 100% stable.

What is the correct way of overclocking?

There is none! Everyone has his own way of doing things, what i do is this:

(Optional) Startup Trepn Profiler for Feedback on CPU clocks and throttling.

Start Kernel Tuner and go into CPU settings: This is important to keep all 4 cores awake! This also shows the Core Temp.

Start NoFrills CPU Control and Set Maximum Clock to desired Clock (in this case 1512mhz) Leave Minimum clock at default, Governor should NOT be Performance / BatterySave / Min Max, every other governor that scales trough a few frequencys is OK

Start IncrediControl, and change the Voltage of the current Frequency. Just decrease the current Voltage by 25mV

Start AntuTu Benchmark and do a Stress Test, if the phone is stable for more than 15-30 seconds, check your Temperatur, if the Temperatur is NOT increasing anymore stop benchmark and quit Antutu.

Make sure the phone relaxes and clocks down, do some normal activity, open launcher, take a screenshot... (10-20 seconds)

If Everything works! Congrats, go to Incredicontrol an decrease the Voltage by another 25mv

Repeate Step 4-7 untill the phone crashes.

After the phone rebooted do everything again from step 1, just take the Voltage you last used +25mV and most of the time you're Stable!

Repeat everything with the next frequency.

Benchmark Stable and Daily usage Stable:

This above was Benchmark Stable! Because switching frequencys a lot and using NFC / WiFi / 3G Bluetooth or a lot other things might cause a crash you have to test this frequency/voltages in daily usage.

If you encounter a lot of crashes there are two ways. The Easy Way, The Proper Way!

Easy Way: Increase on the whole Voltage table +25mV or even +50mV, this should make it stable.

The Proper Way: because its most likely only one or two frequencys that could need a little more Voltage you have to figure out which one causes the crash! The More crashes you have the easier to figure out.

Split the Voltage table in half! Lower and Upper frequencys. 192-810 and 918-1512 leave one half on stock voltage, and use undervolted settings on the other half! If it still crashes you know its in the one you undervolted . In case we set original Voltage on 918-1512 and Undervolted on 192-810 and it sill crashes we know its cause by one of this frequency. in that case again Split in two 192-486 and 594-810, and leave stock voltages on 594-810 and undervolt on 192-486, if it still crashes you know its one of these 3 frequencies. Test each of these 3 frequencys alone, and see if you have crashes.

This might take a few days to figure out, but its the only way to be absolutly sure.

Short notice about OC:

You won't be able to overclock to 1944mhz because your phone will throttle really soon!

Check that out via Trepn Profiler. Even when Antutu benchmark says you have 1944mhz, if you didn't set Kernel Tuner to CPU settings that mostly didn't even affect all CPU cores, and throttled down to 1242mhz or even 1026mhz.

The only way to keep 1944mhz stable is to put the Phone into a Fridge for 20-40 minutes and get -20°C battery Temp and around 10-20°C Core Temp! Or you could put your phone into an ice block.

GPU Overclocking:

The same Problem applys to GPU Overclocking. The Adreno 320 in our APQ8064 is extremly hot! So even when you overclock just a little it whil start throttling nearly immdeiately. If you still want to try....

You need the Root explorer and go to the folder "/sys/devices/platform/kgsl-3d0.0/kgsl/kgsl-3d0/" and open the file "max_gpuclk" with an editor.

This should show the Value "400000000" You can change this Value to either "487500000" or "533333000" save the file, make sure your phone does not idle the GPU (aka start up benchmark really fast!)

You can check the current GPU clock by Doomlords awesome SmallAPP.

Here a Pictures of FireStrik Benchmark OC 533mhz GPU and 1944mhz CPU on a 4.1.2 ROM vs 400mhz GPU and 1512mhz CPU on 4.2.2 (the grey values indicate whats normal for other users who uploaded Xperia Z Benchmarks!)

What are good values?

I don't know! Every phone is different, even if you have the same stock voltage levels (PVS1-3) (find out what PVS is here) that does not mean you can use the same Voltage as the others.

thats all i wanted to say :) Hope it helps someone.

You think this is usefull? Did i miss something crucial? please tell me your opinion. :cowboy: