Lenovo ThinkCentre M91p Ultra-small Desktop PC

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TEST METHODOLOGY

Software and Measurement/Analysis Tools:


Device listing.

Testing Procedures

If available, the latest motherboard BIOS is installed prior to testing. Certain services/features like Indexing, Superfetch, System Restore, and Windows Defender are disabled to prevent them from causing spikes in CPU/HDD usage. We also make note if energy saving features like Cool'n'Quiet/SpeedStep or S3 suspend-to-RAM do not function properly.

Our test is a simple one, determine the overall AC power consumption, noise level, and heat output and at various states. To stress the CPU, we use either Prime95 (large FFTs setting) or CPUBurn depending on which produces higher system power consumption. To stress the IGP, we use FurMark, an OpenGL benchmarking and stability testing utility.

Test Results

System Measurements
System State
Temps
Power (AC)
dBA @1m
dBA @0.6m†
CPU
HDD
Ext*
Off
N/A
2W
N/A
Sleep (S3)
N/A
4W
N/A
Idle
34°C
32°C
27°C
22W
20
24
H.264 Playback
35°C
32°C
26°C
29W
20
24
CPU Load
69°C
33°C
30°C
78W
24
28
CPU + GPU Load
78°C
34°C
32°C
92W
24
28
Ambient: 22°C, 10~11 dBA.
*External temperature measured using an IR thermometer pointed at the hottest portion of the chassis.
We measure SPL at 0.6m for all devices meant to be used atop a desk, as it is more realistic a distance than the usual 1m. It also corresponds to the "seated user SPL" distance specified in the computer noise measurement standard ISO 7779.

Both the Core i5-2500S processor and the included 150W AC power adapter are very energy efficient. The M91p to consumed an impressive 22W when idle and 92W on full load, far less than a desktop using a traditional internal power supply. The hard drive, despite being positioned just above the CPU heatsink stayed under 35°C throughout testing and the case didn't heat up much either. CPU temperatures were not great on load, but that was to be expected given the system's tight confines.

We were concerned that noise would be an issue, but the system wasn't terrible loud considering the performance of the CPU and the form factor of the case. The machine generated 20 dBA@1m (24 dBA@0.6m) at idle and during H.264 video playback, and 24 dBA@1m (28 dBA@0.6m) on load. The BIOS lacks customizable fan control options and no tool we tried could monitor the fan speed, but the exhaust fan seemed to ramp up very gradually as the system heated up.



The Lenovo ThinkCentre M91p measured 24 dBA@0.6m and 28 dBA@0.6m when idle and on load respectively.

While the overall noise level was decent, the quality of the noise left much to be desired. At 0.6m inside our anechoic chamber we could detect an audible rattle and buzzing coming from the fan's motor. Small, high speed, ball bearing fans aren't typically smooth sounding, but it wasn't solely responsible for the noise being generated. The system produced a noticeable hum caused by hard drive vibration passed onto the case; We could feel the exterior shaking slightly. The CPU/VRM circuitry also generated some coil whine, a high-pitched squeal that presented at idle only, disappearing once any type of CPU load was introduced. This too was audible at 0.6m but dissipated with distance.



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