A1286 820-2915-B CPU throttling

[cruiser_]

Good spot and an interesting idea. I wouldn't be surprised if Apple actually implemented something like that

[gurangax]

Maybe its looking for battery full charge capacity of more than 7000mAh for it to enable full speed

[cruiser_]

Re: A1286 820-2915-B CPU throttling

Finally, SOLVED!!!

Put it on a shelf for some time and in the meantime I got my hands on a replacement A1382 battery made by 2power. Yes, a non-genuine Chinese knock off...

Lo and behold, no more throttling!!!

So new replacement A1382 battery from unknown manufacturer, even though correctly reported, charging up and in 'good' OS condition = throttling
Original battery from A1278 (same connector but different capacity) = throttling

Turns out that apart from GPU throttling issue which was the initial problem, the last piece of the puzzle was 'incompatible' battery. This is unbelievable. Gotta love Apple...

I wonder what they did exactly... blacklisted the serial?

'throttling' battery #1

Model Information:
 Serial Number:	W01484ND2D3BA
 Manufacturer:	SMP
 Device Name:	bq20z451
 Pack Lot Code:	0
 PCB Lot Code:	0
 Firmware Version:	201
 Hardware Revision:	000a
 Cell Revision:	158
 Charge Information:
 Charge Remaining (mAh):	6575
 Fully Charged:	No
 Charging:	Yes
 Full Charge Capacity (mAh):	6976
 Health Information:
 Cycle Count:	5
 Condition:	Normal
 Battery Installed:	Yes
 Amperage (mA):	577
 Voltage (mV):	12466

Original A1278 battery (throttling):

Model Information:
 Serial Number:	W053001C9D3BB
 Manufacturer:	SMP
 Device Name:	bq20z451
 Pack Lot Code:	0
 PCB Lot Code:	0
 Firmware Version:	201
 Hardware Revision:	000a
 Cell Revision:	158
 Charge Information:
 Charge Remaining (mAh):	4837
 Fully Charged:	Yes
 Charging:	No
 Full Charge Capacity (mAh):	4927
 Health Information:
 Cycle Count:	1805
 Condition:	Normal
 Battery Installed:	Yes
 Amperage (mA):	0
 Voltage (mV):	12441

2power battery (working fine!)

 Model Information:
 Serial Number:	C01514309YEF90MA4
 Manufacturer:	2-power
 Device Name:	A1382
 Pack Lot Code:	3230
 PCB Lot Code:	30db
 Firmware Version:	ddae
 Hardware Revision:	dac2
 Cell Revision:	2b39
 Charge Information:
 Charge Remaining (mAh):	7359
 Fully Charged:	Yes
 Charging:	No
 Full Charge Capacity (mAh):	7360
 Health Information:
 Cycle Count:	1
 Condition:	Normal
 Battery Installed:	Yes
 Amperage (mA):	0
 Voltage (mV):	12233

[cruiser_]

Re: A1286 820-2915-B CPU throttling

so i spent a few hours on this again today - down to looking at SMBUS communications between SMC and U55* chips with logic analyzer.
All looked fairly ok.
Was suspecting 'airport proximity' readings to be wrong but it was a dead end.

i am now chasing rabbit hole of not having reads on VN0R, TG1D & TW0P.

@gurangax can you please check if you are getting the values at all? Presumingly you are on MBP8,2/EMC2563?

[gurangax]

Re: A1286 820-2915-B CPU throttling

Nah, haven't got around to it again. My hope sits with nongen battery but that is a long shot
Do you have a genuine battery?
Is you GPU working fine? Mine is and I don't want to remove it just to prove the theory.
I can imagine it could pull SDA/CLK lines if it were shorted, that could cause throttling since no temp reading could be made

Yup I have genuine original battery which comes with laptop. I bought this laptop for cheap from a guy who stored it after the screen went black. Turns out that it has been repaired before and I guess he doesnt want to repair it anymore probably because of high repair cost. The GPU was shorted before, it got too hot. So I removed the power coils for GPU core. that solve the problem which prevented the laptop to turn on. Soon (maybe a week later) it starts to throtle after using the cpu for high demanding app for long periods.

[cruiser_]

Re: A1286 820-2915-B CPU throttling

Just have this problem today. throtled cpu. did you fix yours?

Nah, haven't got around to it again. My hope sits with nongen battery but that is a long shot
Do you have a genuine battery?
Is you GPU working fine? Mine is and I don't want to remove it just to prove the theory.
I can imagine it could pull SDA/CLK lines if it were shorted, that could cause throttling since no temp reading could be made

[gurangax]

Re: A1286 820-2915-B CPU throttling

Excellent! Thanks for the update. Did you apply any special board straps after the GPU was removed?

sorry i dont get what you mean. i didnt put anything but just thermal pad for electrical insulation for the gpu heatsink, if thats what you meant.

[mon2]

Re: A1286 820-2915-B CPU throttling

Excellent! Thanks for the update. Did you apply any special board straps after the GPU was removed?

[gurangax]

Re: A1286 820-2915-B CPU throttling

I solved mine. It turns out that the discrete GPU even though it has been disabled through the efi bios and resistor mod, can give out many other problems. This includes cpu throtling. In the end i simply removed the GPU chip and my problems is solved. It passed ASD check no errors found so the GPU removal was my last option.

[gurangax]

Re: A1286 820-2915-B CPU throttling

this is super fun

I removed Q5059 - it pulls down CPU_PROCHOT_L if SMC_PROCHOT is high. No more CPU_PROCHOT_L being low, but lo and behold, super slow still!

I kept ASD OS running for a few hours, only testing sensors. No odd values reported. I would think ASD should catch any sensors that are off?

Just have this problem today. throtled cpu. did you fix yours?

[cruiser_]

Re: A1286 820-2915-B CPU throttling

this is super fun

I removed Q5059 - it pulls down CPU_PROCHOT_L if SMC_PROCHOT is high. No more CPU_PROCHOT_L being low, but lo and behold, super slow still!

I kept ASD OS running for a few hours, only testing sensors. No odd values reported. I would think ASD should catch any sensors that are off?

[mon2]

Re: A1286 820-2915-B CPU throttling

Locate the thermal sensors for the CPU and confirm it is ok.

[cruiser_]

Re: A1286 820-2915-B CPU throttling

CPU_PROCHOT_L is pulled low after a few seconds after powering on. What the heck...

[cruiser_]

Re: A1286 820-2915-B CPU throttling

Thanks, mon2. I have successfully reprogrammed gmux before with lattice before in bad case of shorted GPU, along with hardware brightness fix. However, don't want to lobotomy this board if I'm not 100% this is the culprit ;/
Tried two different batteries from a1278, no joy.
Fans hover around 2k rounds, would xpect them to be high.
Must be missing something obvious...

[mon2]

Re: A1286 820-2915-B CPU throttling

Google 'dosdude1' and you will find his bypass method for this model and how to disable the defective GPU. I recall that we donated to him a few times and his method worked for us.

Here is a (very) long thread on the topic:

https://forums.macrumors.com/threads...ypass.2134019/

but check out his main website as the above I believe is dated. He has better options.

and another (we have not tested this method - JTAG to reflash the MUX):

https://www.youtube.com/watch?v=n6ROPL2-5HA

[cruiser_]

Re: A1286 820-2915-B CPU throttling

a wee update... it looks as if it is dGPU related. Somewhat.

Was going through some possible throttle 'alerts' and found that U5550 lowers GPUTHMSNS_ALERT_L during boot up.
So I disabled dedicated GPU (with nvram stuff) & removed AMDRadeon drivers.

Now the GPUTHMSNS_ALERT_L stays high, yet the CPU throttling is still there

[cruiser_]

Re: A1286 820-2915-B CPU throttling

Don't think it's the same issue. Never had any errors in ASD, dGPU is working fine no glitches no slowdowns or hangs etc.
From time to time I am seeing 'jerky' cursor behaviour even in boot choice screen, where ext GPU isn't used.
Tried booting with no touchpad and keyboard, same throttling

I don't have original battery to try unfortunately as was also suggested in that post ;,(

[mon2]

Re: A1286 820-2915-B CPU throttling

Review the link above from the Rossmann forums. Appears to be the same issue as yours.

Try a SAFE MODE BOOT as well. The GPU is likely to blame.

[cruiser_]

Re: A1286 820-2915-B CPU throttling

Yup, exactly this one. Was shorted drain-source. Replaced now.

[mon2]

Re: A1286 820-2915-B CPU throttling

That is Q7055 in my schematic for 820-2915-B.