By Daniel Eran Dilger

Published: 05:00 PM EST (02:00 PM PST)

iFixit's teardown of the Verizon iPhone 4 reveals the use of Qualcomm's MDM6600 chip, a "world mode" baseband capable of supporting both CDMA/EVDO and GSM/UMTS networks, although the phone is still CDMA-only.

Prior to the discovery posted by the takeapart experts at iFixit, the new phone was expected to use a Qualcomm MDM (Mobile Data Modem) chip as its baseband processor in order to work on Verizon's CDMA-style network, but the revelation of its world mode chip is new, even if the phone's design prevents it from being used on both networks.

Is a phone without a SIM just as sweet?

iFixit points out that the new model lacks a SIM card slot necessary to be used on GSM/UMTS networks such as AT&T or Apple's other existing carrier partners globally. It also reasons that the new phone is limited to CDMA-only operation because supporting multiple mobile antennas would be more complex to fit in the existing phone's design.

Motorola's Droid Pro uses the same chip to work both on Verizon and roam globally on GSM carriers, but it is also taller, wider and thicker than iPhone 4, even while supplying a smaller screen.

The lack of a SIM slot also greatly complicates the efforts of Verizon iPhone 4 users to unlock the phone for use on other carriers, compared to the relative ease of unlocking previous iPhones for use with another company's SIM card (note that unlocking is not the same as jailbreaking, which removes the OS security of the computer side of the phone attached to the baseband modem.)

According to one report, unlocking Verizon's iPhone 4 will be virtually impossible to do because it would require using "an ESN/MEID from a donor phone with service. This technique is a US federal crime."



Unlocking CDMA phones from one provider and using them on another requires the support of both carriers. This is done, for example, by Verizon for its MVNO partners like Cricket or MetroPCS for some phones, although its unlikely that Verizon will support this with iPhone 4, at least initially.

Any possibility of using iPhone 4 on other CDMA carriers, from Sprint in the US to foreign carriers in China and India, will realistically require agreements between the carrier and Apple.

Other difference in the Verizon iPhone 4

The Verizon version of iPhone 4 partitions the "wrap around" antenna design of iPhone 4 into four segments rather than the three used on the existing version.

This allows it to support the 800 and 1900MHz CDMA EVDO bands used by Verizon, opposed to the existing version, which must support four GSM bands (850, 900, 1800 and 1900MHz) and four UMTS bands (850, 900, 1900, 2100MHz) to work across both US and foreign carriers' networks.

Initial reviews have noted that, just as with other phones on the market, one can still attenuate the signal by holding the phone in various ways, but that Verizon's service very rarely ever got weak enough to make that effect noticeable, let alone the problem that some AT&T users had to carefully account for to avoid dropping a call.

Apple describes the new model as lacking any user serviceable parts, and now uses "pentalobe" screws to deter users from opening up their phone. That makes cracking the device open dependent upon a specialty screwdriver that's even harder to find than the tiny precision Phillips screwdriver needed for the screws Apple had been using.

The logic board of the new iPhone 4 is entirely new, rather than simply sporting a drop-in style replacement of the different baseband chip. Even the shape is changed, in order to accommodate a new vibration motor for silent alerts.

"Rather than using a rotational electric motor with a counterweight," iFixit's report notes, "the Verizon iPhone appears to utilize a linear vibrator for call/message alerts." The site adds "our tests show that the new vibrator has quieter, softer feel, and makes a better sound when on a table."



On page 2 of 2: Repairability, WorldMode/4G iPhone 5.