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Unusual throttling behavior shows the Core i7-8565U running both faster and slower than the i7-8550U

New Dell Inspiron 17 7786 can run slower than the last generation Dell Inspiron 17 7773
New Dell Inspiron 17 7786 can run slower than the last generation Dell Inspiron 17 7773
The new Dell Inspiron 17 7786 can run 20 percent faster than the last generation Inspiron 17 7773 for the first 10 to 20 minutes before clock rates begin to dip dramatically. At that point, CPU performance stabilizes at 10 percent slower than the older Core i7-8550U CPU. This "delayed" throttling behavior is uncommon on many laptops.

Yet another laptop has fallen victim to CPU throttling. After discovering performance discrepancies between the Core i5 and Core i7 SKUs of the ThinkPad tablet and EliteBook convertible, similar results can be observed on the new 17.3-inch Dell Inspiron 17 7786. More specifically, its Core i7-8565U Whiskey Lake-U CPU can perform slower than the Core i7-8550U in the last generation Dell Inspiron 17 7773 that it directly supplants.

To show this, we ran CineBench R15 Multi-Thread in a loop on both the Inspiron 17 7786 and 7773 with our results recorded below. The newer 7786 is able to maintain faster clock rates than the 7773 for the first 15 loops or so and the higher CineBench scores during the first half of the stress test reflect this. After some time has passed, however, the 7786 drops from 613 points all the way to 424 points to represent a performance dip of 30 percent. The 7786 never fully recovers and overall CPU performance remains lower than the 7773.

This throttling behavior is notable because it doesn't occur until much later in the stress test. In comparison, the 7773 begins throttling immediately after the first or second loop before stabilizing much sooner than on the 7786 as shown by the comparison graph below.

Users who intend to run heavy CPU workloads for long periods on the Inspiron 17 7786 should be wary of sudden performance degradation after 10 to 20 minutes of stress. For the average consumer who just wants to use the convertible for web browsing and multimedia playback, however, the throttling should have almost no impact on daily performance.

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Dell Inspiron 17-7786 Intel Core i7-8565U, Intel Core i7-8565U: Ø516 (424.95-657.14)
Dell Inspiron 17-7773-0043 Intel Core i7-8550U, Intel Core i7-8550U: Ø516 (503.63-652.06)
Acer Aspire 5 A517-51G-80L Intel Core i7-8550U, Intel Core i7-8550U: Ø546 (539.34-584.93)
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> Notebook / Laptop Reviews and News > News > News Archive > Newsarchive 2019 02 > Unusual throttling behavior shows the Core i7-8565U running both faster and slower than the i7-8550U
Allen Ngo, 2019-02- 4 (Update: 2019-02- 5)
Allen Ngo
Allen Ngo - US Editor in Chief
After graduating with a B.S. in environmental hydrodynamics from the University of California, I studied reactor physics to become licensed by the U.S. NRC to operate nuclear reactors. There's a striking level of appreciation you gain for everyday consumer electronics after working with modern nuclear reactivity systems astonishingly powered by computers from the 80s. When I'm not managing day-to-day activities and US review articles on Notebookcheck, you can catch me following the eSports scene and the latest gaming news.