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

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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