Symptoms of problem
Model # Dell E6430s with Intel i7-3520m processor with 8 GB RAM running windows7 64 bit ultimate.
Slow performance on large computational tasks: video processing, speech recognition, and excel pivot charting.
Low windows experience index for CPU 4.9 versus expected 7.2 for i7-3520m CPU (2.9 GHz)
Low voltage on the chip in the CPU-Z monitor
Observations of Problem:
The windows experience rating can only be performed while running on AC power.
Windows Resource Manager only showed CPU Maximum Frequency of 75% on AC power
CPU-Z monitor showed the CPU multiplier constantly stuck at 12 when running on AC power which translates to 1.2 Ghz CPU speed.
downloaded CPU-Z from http://www.cpuid.com/softwares/cpu-z.html
When unplugged from AC power the CPU multiplier would jump to 34 which translates to a 3.3 GHz CPU speed. The problem appeared only when the machine is running on AC power.
It limits the CPU multiplier to 12 (the minimum)
Steps to resolution
Swapped external AC power supplies – no change
Ran all Dell diagnostics via F12 at boot – all passed
Ran all Intel CPU diagnostics (downloaded file) – all passed
Changed setting in bios for CPU speed step and power management – no change
Changed all windows power management settings to every combination – no change
Upgraded BIOS – no change
Upgraded chipset drivers – no change
Upgrade Video drivers – no change
Dell wanted me to reload windows7 – refused
Dell replace motherboard and embedded CPU – fixed
Discussion of underlying problem
I had the original Dell power supply and it was recognized as a Dell product, so I had some other motherboard issue.
Dell has logic on the motherboard to control the power to the CPU that is ACPI compliant (advanced configuration and power interface)
Windows Experience Index Improvements
CPU 47% increase from 4.9 to 7.2
RAM increase 9% from 7.0 to 7.6
Graphics increase 30% from 5.0 to 6.5
Gaming increase 16% from 5.6 to 6.5
CPU-Z CPU Improvements
283% improvement for very CPU intense tasks, increase from 1.2 to 3.4 GHz
CPU now goes to 112% maximum frequency in windows resource manager.
Before the fix it maxed at about 75%.
Updated my answer. – AndrejaKo – 2011-10-09T10:04:08.417
2Too many processes in the background could definitely cause this, but you would've had to have installed something, or be running something at the time on both laptops when you ran the test to cause such a low CPU score. Something like a game, P2P software, video editing, or something very intensive would have to be running during the test. That's why I said to run the test with "all other applications closed". – bwall – 2011-10-10T17:45:37.883