S-XPS 1645 AC Power Throttle Issue Investigation

[ikjadoon]

Originally Posted by eblock12

Yeah I had tried disabling PowerPlay too, it was one of the first things. It kinda "fixes" the issue in that it locks the GPU into a "medium" clock rate and it doesn't draw enough power anymore to hit the issue. You need to stress the CPU and GPU at the same time. However, it may be an acceptible workaround for you if you're running a less intensive game.

I was talking about SpeedStep/EIST, not PowerPlay. PowerPlay = GPU ; SpeedStep/EIST = CPU.

~Ibrahim~

[Siphen]

Originally Posted by ikjadoon

I was talking about SpeedStep/EIST, not PowerPlay. PowerPlay = GPU ; SpeedStep/EIST = CPU.

~Ibrahim~

If you disable speedstep it locks the CPU at it's slowest setting.

The 130w slim was the one I linked to

[Tonkadan]

Where can I disable PowerPlay and SpeedStep?

On another note i found something strange that may be related to the power supply problem.

I was playing Assasin Creed without the AC adaptor on max performances and full brightness. About an hour later, as expected Windows told me that I must connect the laptop to a power source because I was running out of battery. At this time the Windows battery indicator was at 10% so I plugged in the AC adaptor (didn't see any lag on the game..) but 10 minute later the game stopped and my computer wanted to shut down. I double clicked on the battery icon on the task bar and the level was at 3% and showing (3% - Plugged In - Not charging). I tried rebooting the laptop but I got a message just after the Dell logo telling me that my laptop could not charge the battery because the battery was not recognized.

After a complete power cycle I was able to boot the laptop and now my battery is charging. Strange....

[khaledseif]

Consistent with what we have found so far. At full load the charger is not supplying enough power to the machine and not able to charge the battery.
I found that the charging rate rate was 5mW while playing.

[khaledseif]

@Ibrahim
RGBLED is not the cause of the problem as several people with WLED including me are reporting the problem.
RGBLED consumes more power and this is the reason the performance drop is more severe for the people with RGBLED.

[ikjadoon]

@Siphen

Yeah, I've found that disabling it in the BIOS causes the CPU to be locked to 7x on the i7-720QM. But disabling it in Real Temp allows the CPU to run at 13x, full brightness, adapter plugged in whereas it on makes the CPU bounce between 8-11x.

@khaledseif

Right...I think, Zlog, it might be best, then, to change the first post to brightness and remove the words 'RBG'.

@Tonkadan

PowerPlay can be disabled/enabled in CCC. SpeedStep can be disabled/enabled in the BIOS or in Real Temp. The difference, at least for me, is noted above in my response to Siphen.

~Ibrahim~

[khaledseif]

Originally Posted by ikjadoon

@khaledseif

Right...I think, Zlog, it might be best, then, to change the first post to brightness and remove the words 'RBG'.


@Tonkadan

PowerPlay can be disabled/enabled in CCC. SpeedStep can be disabled/enabled in the BIOS or in Real Temp. The difference, at least for me, is noted above in my response to Siphen.

~Ibrahim~

Some people reported that there is no performance drop if the LED is turned off and an external monitor is connected. I think Brightness increase the power consumption which makes it worse but not the main suspect.

Are you stressing the CPU only or both the GPU and the CPU. I am using Crysis benchmark on window and prime95 to stress both.

Disabling PowerPlay lets the GPU to work at a max of 300 vs the max 675 which will decrease power consumption. It is the case when you use power saver plan or DELL recommended on battery.

I found that the performance for the different plans as follows
Maximum brightness, Crysis GPU benchmark on high in window mode, Prime95 to stress the CPU, RivaTuner to monitor the GPU, RealTemp to monitor the clocks, and BatteryMon to display the discharging rate. 100%CPU and 100%GPU load.

1. Power saver
on battery
GPU 300 CPU at 7x
on charger
GPU 300 CPU at 12x

Observation
on charger performs better

my analysis
The power saved from underclocking the GPU helps in improving the power for the CPU.

2. DELL recommended
on battery
GPU 300 CPU at 11-12x
on charger
GPU 675 CPU at 7-10x
with GPU switching from time to time when CPU is at 7x due to lack of CPU orders

Observation
on battery is slightly better

My analysis
Battery provide enough power while the charger sometimes doesn't provide enough power which lead to the downclock of the CPU. the sudden downclock of the CPU lead the GPU to sense a decrease of activity and downclocks to 300.

3. Maximum Performance with PowerPlay changed to maximum performance under battery in the advanced power options
on battery
GPU 675 CPU at 11-12x
on charger
GPU 675 CPU at 7x

Observation
on battery is 20-30% better

My analysis
Battery provide enough power while the charger doesn't provide enough power which lead to the downclock of the CPU.

My conclusion is either the charger or BIOS, with the charger being my first suspect as it simply doesn't charge in Dell recommended and High Performance, and to the reporting that there is no problem on running on an external monitor

[Zlog]

Ikjadoon, are you still getting general stuttering performance with speedstep off and can yo uconfirm that the CPU DOES reach 13x multiplier? Some one below your post indicated that it gets the CPU locked at 1.6ghz.

[khaledseif]

Envy 15 consumes up to 109.5 watts Link
Studio 1557 with ATI4570 consumes upto 90.2W Link
Dv6t comes is 720p and a more efficient video card, yet equipped with a 120W charger
All the i7 laptops in the market now comes with 120+ watts charger

XPS 1640 +ATI 4670+ P9700 consumes up to 85.4W Link

[DeathWalking]

Originally Posted by khaledseif

Envy 15 consumes up to 109.5 watts Link
Studio 1557 with ATI4570 consumes upto 90.2W Link
Dv6t comes is 720p and a more efficient video card, yet equipped with a 120W charger
All the i7 laptops in the market now comes with 120+ watts charger

XPS 1640 +ATI 4670+ P9700 consumes up to 85.4W Link

Also known as the 1645 definitely consumes more than 90W. I don't care what Zlog says about TDP and electrical wattage. He's absolutely right that you don't know exactly how much wattage the chip is using, but TDP is rating of waste heat watts at max load. Since one watt of heat has to come from a watt of electricity, you are guaranteed at least 45 watts of electricity draw at load from the CPU. Add that to the (probable) increase power draw of the RGB screen, plus the fact that we're using a 4670 over the 4570 that combined with a C2D to draw 90.2...we're definitely drawing over 90.

I have no substantiation for even thinking this, but I've been afraid that the charging circuit won't be able to use as much current as we need it to! I'm really looking forward to the 130W test.