
If we go by what Gartner analyst Ken Dulaney told iPod Observer, then Apple has ordered a second round, amounting to 10 million iPhones based on the 3G network. Apparently Ken's job is to keep a tab on iPhone developments for Gartner and he has based his observations on the rumors floating around in Asia. This second order is in in addition to the ten million first generation iPhones that Apple has said it will sell by the end of 2008. Ken also speculates that the 3G iPhone will use an Organic Light Emitting Diode (OLED) display making the body thinner plus consuming lesser power.
Reports also suggest that Apple didn't do that well in Europe with the 2.7G/EDGE network phone, hence the big movement to the 3G network iPhone.
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