Because TSMC still can't get enough 28nm HKMG wafer out - pay attention to TSMC transcript.
TSMC is aiming to increase HKMG output 50% in 2013.
Who says manufacturing does not matter ? for sure it isn't NVDA.
NVDA and AMD will be dogfighting of what is left from discrete graphic while Intel will unleash Haswell.
AMD is paying 6% to get money - they are living off their credit cards.
... Tegra 4 itself will be built on TSMC's 28nm HPL (low-power) process, and the the total die size is around 80mm. ... The i500 will be built on TSMC’s 28nm HP HKMG process....
Nvidia claims that the Icera softmodem approach saves a great deal of die space compared to a hardware radio, but die size isn’t going to be the only consideration. 4G/3G/WiFi radios consume a significant percentage of a smartphone or tablet’s power budget. There are only a handful of smartphones on the market that use Icera’s softmodem tech and none of them have decent battery life.
As far as technical details go, the i500 will be capable of category 3 LTE (100Mbps), WCDMA, HSPA+, EDGE, and GSM. VoLTE is supported as well. Support for category 4 LTE will be added later, via a software update (one of the neater aspects of a softmodem). The i500 will be built on TSMC’s 28nm HP HKMG process.