While the Verizon iPhone is a CDMA-only device, it actually has a chipset capable of supporting both CDMA and GSM.According to the team at iFixit, the CDMA Verizon iPhone uses a Qualcomm MDM6600 chip, the same chip used by the Motorola Droid Pro to connect to both CDMA and GSM networks.  iFixit says that the chip supports 3G HSPA+ data rates that max out at over 14Mbps.
Kyle Wiens, the cofounder of iFixit, speculates that the new iPhone doesn't support GSM because it might have been "easier to design antennas for a CDMA-only phone" while also noting that "this phone supports two cellular frequency bands while Apple supports five bands in the GSM version."  Wiens says this is particular significant because it is "a sign that Apple may be considering unifying the CDMA and GSM iPhones in the future."
The Verizon iPhone: Seven key facts you need to know
The iPhone has been a big hit for Verizon so far, as JP Morgan analyst Phil Cusick said today that it had sold over 500,000 units on its first day of release alone.  Verizon first announced it would support the device on its 3G Ev-Do Rev. A network last month.  While Verizon is the only major American carrier to offer 4G LTE services, Apple decided to hold off for a bit before releasing an LTE iPhone, primarily because the first generation of LTE chips is so large that it would have forced Apple to make design compromises on its devices.
As it is, Wiens says that Apple has significantly reworked the interior of its phone for the CDMA iPhone, as it has changed the location and design of its electromagnetic interface shields, connector locations and board layout.  Even so, the CDMA iPhone faces two key limitations that don't affect its GSM counterpart.  First, it can't support simultaneous voice and data transmissions, and second, CDMA networks are far less common in the rest of the world than they are in the United States, so it's more difficult to find connectivity options on the Verizon iPhone when travelling abroad.  The CDMA Development Group has said that it plans to have an updated standard that allows for simultaneous voice and data use sometime this year, most likely by the summer.
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