Daring Fireball: A Tale of Two Modems

By John Gruber

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Day One — The journal you actually keep. Start with a chat, end with a journal entry. ⭐ 4.8 (400k)

A Tale of Two Modems

Wednesday, 1 July 2026

Marko Zivkovic, reporting for AppleInsider regarding some of the data revealed by Tata Electronics’s massive data breach:

For the U.S. variant of the iPhone 18 Pro, which will feature<br>mmWave compatibility, Apple seemingly plans to use Qualcomm modem<br>hardware. Multiple Qualcomm components, including the SDX80M,<br>SDR875, QDM8771, QDM8720, PMK75, PMX75, and QET7100A, are<br>referenced in a bill of materials related to the iPhone 18 Pro<br>model Apple plans to sell in the United States.

As for the iPhone 18 models which will be sold elsewhere, Tata<br>documentation suggests these configurations will use Apple’s<br>proprietary C2 modem. While this approach may sound unusual, there<br>is at least one possible explanation.

Apple’s current in-house modems, the C1 and the C1X, do not<br>support 5G mmWave, and it looks as though the C2 will continue<br>this trend. Until Apple develops a modem compatible with mmWave,<br>it looks as though the company will offer mmWave support to iPhone<br>18 Pro users by using Qualcomm hardware.

This immediately raises the question of which modem is “better”, and I suspect the answer requires nuance. Apple’s C1 and C1X modems are, by all accounts, noticeably more power efficient than Qualcomm’s. An iPhone with an Apple C-series modem should get longer battery life than an otherwise identical iPhone with a Qualcomm modem. The obvious advantage to the Qualcomm modems is support for 5G mmWave, the super high-speed 5G bands primarily offered by Verizon.

Personally, I don’t care about mmWave speeds. It literally makes no difference in my experience compared to regular 5G speeds. In fact, ever since WWDC a few weeks ago, I’ve had my iPhone 17 Pro set to use LTE instead of 5G. (Settings: Cellular: Cellular Data Options: Voice & Data.) I literally notice no difference in speed and I presume that battery life is improved. Battery life certainly isn’t worse. (I switched to LTE after a friend at WWDC suggested that LTE has better range/penetration in places like airports, especially when you’ve boarded a plane but haven’t taken off yet.)

Just now I used Ookla’s Speedtest app to test the difference here in my office. I got 80 Mbps down / 15 Mbps up on LTE; 320 Mbps down / 18 Mbps up on 5G. That’s on Verizon’s network (which does offer mmWave throughout center city Philly, but seemingly not here at my house), with my iPhone 17 Pro (which uses a Qualcomm modem). I tested again, minutes later, using an iPhone Air (which uses Apple’s C1X modem) and got 390 Mbps down / 21 Mbps up on 5G (and similar 80 Mbps down / 13 Mbps up on LTE).

So 5G is clearly faster than LTE here at home for me, using either iPhone model. But why should I care about that difference? Having a phone that can pull 320 Mbps down over cellular is like having a car that can go 320 MPH — an interesting technical feat, but of no practical value to me whatsoever. I never feel like I’m waiting for anything to load because I’m on LTE. LTE is fast enough, and regular 5G is more than fast enough. 5G mmWave is simply a waste of battery life as far as I’m concerned.

So Apple’s C-series modems win on battery life, and Qualcomm’s modems win for high-speed mmWave support. But Qualcomm’s speed edge is theoretical, not practical. Apple’s C1/C1X energy efficiency edge is very much practical. I’ve used both the 17 Pro and iPhone Air in a variety of places over the last year, and I’ve noticed no real difference in being able to get a decent signal in rural areas, either.

On the surface it sounds like a tradeoff — that Qualcomm’s modems consume more battery but deliver higher download speeds. But in practice that tradeoff only comes into play if you’re a Verizon user and happen to be within 50 meters or so of a mmWave-equipped cell tower, and that crazy high bandwidth doesn’t really make anything you do with your phone any faster than regular 5G (or LTE, I say). In reality I’d rather have an Apple C-series modem — I’d get better battery efficiency all the time, the same network performance almost all the time, and I don’t care at all about the rare times when I could get the crazy-high-speed mmWave bandwidth that Apple’s C1 and C1X modems don’t support (and perhaps still won’t support with the upcoming C2). Cellular download speed and reception is nearly a solved problem for my needs. Battery life is not.

So why wouldn’t Apple just use the C2 everywhere, including the U.S.? I suspect Apple is hoist not with their own, but with Verizon’s petard here. Faster-than-you-practically-need download speeds are a carrier bragging point. Longer battery life and plenty-fast-enough download speeds are an Apple bragging point. Verizon — and to a lesser extent, AT&T — spent a...