Apple has yet to explain—or really say anything about—its decision to use a wireless modem chip made by Intel in some models of the new iPhone 7.

In last year’s iPhone 6S, Apple exclusively used modems from Qualcomm, which has been a market leader in wireless chip technology for decades. But this year, Apple opted to switch to an Intel modem chip for the portion of iPhone 7 models destined for use on AT&T and T-Mobile networks. Intel has only recently ramped up its effort to crack the wireless modem business.

It was already known that the Qualcomm iPhone 7 models have the ability to connect to more kinds of carrier networks than the Intel iPhone 7 models. Now comes news that the iPhone 7 with the Intel modem chip actually performs worse in download speeds than the model with Qualcomm’s chip.

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Phone testing firm Cellular Insights put both versions of the iPhone 7 through a battery of tests designed to measure how well the two modems connected to a wireless network at varying signal strengths. The aim was to simulate real world conditions, such as when a phone user is close to a cell tower and has a strong signal as well as when the user is farther from a tower and is connecting to a weaker signal. The firm also conducted the tests in three different LTE spectrum bands, because different countries and carriers offer LTE service in different bands.

The results showed that, nearly across the board, the iPhone 7 with the Qualcomm modem made stronger connections to the network that the Intel-toting model. On average, the Qualcomm chip outperformed the Intel chip by 30%. At the extreme, in the weakest signal simulation, the Qualcomm chip performed 75% better.

That means consumers with an iPhone 7 Qualcomm model could download files faster and get a connection in more places than those who had the iPhone 7 Intel model.

To see a demonstration of the iPhone 7, watch:

“In all tests, the iPhone 7 Plus with the Qualcomm modem had a significant performance edge over the iPhone 7 Plus with the Intel modem,” the firm concluded in its report on the two models. “We are not sure what was the main reason behind Apple’s decision to source two different modem suppliers for the newest iPhone.”

Intel and Qualcomm declined to comment.