The Snapdragon S4 processor was made at 28nm, and since 28nm is a brand new process for Global Foundries (Qualcomm’s main foundry) and also for TSMC, which means that some unexpected issues may appear, or their planned production is much smaller than anticipated. This has already led to phones that were supposed to have the S4 processor, like the One S, to only get an S3 processor (although clocked at 1.7 Ghz) in certain Asian markets.
Qualcomm may have put the S4 processor on a high-priority list for certain phones models, like the One X and the US version of the Galaxy S3, since they can’t give everyone the S4 chip, even if they are asking for it. The S4 chip is popular not just because of its next-gen architecture, and higher performance, but also because of its integrated modem, which makes it cheaper and more efficient overall.
But Qualcomm has found a solution to increase the supply of the S4 and the rest of of their 28nm-made chip lineup, by partnering with TSMC, the world’s largest foundry, as well as other foundries who can deliver them 28nm chips.
The fact that Qualcomm is experiencing supply issues because of the lack of a mature 28nm is not bad news for them, but also for other companies who were using these foundries, like Texas Instruments and their expected OMAP 5 processor. Samsung is going to bypass this whole issue because they are making their own chips, and their Exynos 5250 processor will probably be made at either 28nm or 32nm, like the Exynos 4 quad.