Update 9/18: We discovered that the product page for the Japanese (Qualcomm) model of the iPhone 8 claims the phone has 800Mbps LTE, which is better than the 600Mbps we thought it had. That note is missing from the product pages for the two models of the phone which will be available in the US.

This doesn't change our recommendation—it's better to get an all carrier-compatible phone than a some carrier-compatible phone—but it throws into question what the overall LTE capabilities of these phones will be. We'll see when we get to test them.

Original Story 9/15:
Apple did it again. With the iPhone 7 generation, Apple split its modem orders across Qualcomm and Intel. Because Intel's modems don't support the CDMA system used by Sprint and Verizon, the Intel versions of the phone couldn't connect to those carriers.

The tech specs for the iPhone 8, 8 Plus, and iPhone X look like Apple is taking the same strategy, though Apple has not confirmed its modem suppliers. First, let's note that the three phones seem to have the exact same LTE capabilities.

The modems, as listed, aren't exactly cutting-edge. While they include Band 66, used by T-Mobile and Verizon, they lack T-Mobile's new Band 71, which the carrier is using to extend rural coverage. (Right now, only the LG V30 has Band 71.) There's no word on whether or not the phone supports Sprint's coverage-extending HPUE technology.

But the split between CDMA/non-CDMA looks like confirmation that Apple is using some mix of an unnamed Qualcomm modem and the Intel XMM7480, which doesn't support CDMA. The XMM7480 has a maximum speed of 600Mbps, because it also doesn't support 4x4 MIMO, one of the three components of Gigabit LTE. If what we saw with the iPhone 7 holds, the Qualcomm model will be limited to the same basic modem features as the Intel unit.

That's going to put the iPhone 8/X noticeably behind the Samsung Galaxy S8 and LG V30 when it comes to LTE efficiency and speeds. It'll be on par with the Essential PH-1, which an analysis earlier this week showed also hits the 600Mbps mark. Yes, we know that none of these phones hit 600Mbps or a gigabit in real life. But as we saw in our Fastest Mobile Networks tests, faster modems are still faster in real-life conditions.

The CDMA-lacking version won't just mean you can't connect to Verizon and Sprint. It also locks you out from Virgin, Boost, and low-cost carriers like Tello, Total Wireless, and Twigby that use those networks.

As we saw with the iPhone 7, your best bet is to get a Verizon or carrier-free unit of the iPhone 8/X, which will come with the more flexible modem. (All Verizon phones are unlocked.) We hope to get more details as the phones become available; Sept. 22 for iPhone 8 and Nov. 3 for iPhone X.

Here's how the different global models shake out, according to Apple. The only visible difference on the spec sheet is the lack of CDMA. (There is also a Japan-only model.)

Qualcomm Modem

iPhone 8 model A1863; iPhone 8 Plus model A1864; iPhone X model A1865
FDD-LTE (Bands 1, 2, 3, 4, 5, 7, 8, 12, 13, 17, 18, 19, 20, 25, 26, 28, 29, 30, 66)
TD-LTE (Bands 34, 38, 39, 40, 41)
TD-SCDMA 1900 (F), 2000 (A)
CDMA EV-DO Rev. A (800, 1900, 2100 MHz)
UMTS/HSPA+/DC-HSDPA (850, 900, 1700/2100, 1900, 2100 MHz)
GSM/EDGE (850, 900, 1800, 1900 MHz)

Intel Modem

iPhone 8 model A1905; iPhone 8 Plus model A1897; iPhone X model A1901
FDD-LTE (Bands 1, 2, 3, 4, 5, 7, 8, 12, 13, 17, 18, 19, 20, 25, 26, 28, 29, 30, 66)
TD-LTE (Bands 34, 38, 39, 40, 41)
UMTS/HSPA+/DC-HSDPA (850, 900, 1700/2100, 1900, 2100 MHz)
GSM/EDGE (850, 900, 1800, 1900 MHz)