TSMC's latest figures show that its largest customer orders in 2021 rose 20 percent to NT$405.4 billion ($14.3 billion), or nearly 26 percent of overall wafer revenue in 2021.

According to Digitimes, market watchers believe that Apple has been TSMC's largest customer, and TSMC has secured orders for almost all of Apple's custom chips used in iPhones, iPads, Apple Watches and other devices.

As Apple shifts its Mac processors from Intel to self-developed, the person pointed out that TSMC is the biggest beneficiary. TSMC has reportedly signed a contract with Apple to manufacture M-series Mac chips.

Observers also said that Apple's just-released iPhone SE, iPad Air, Mac Studio and Studio Display series all use self-developed chips manufactured by TSMC. For example, the M1 Ultra processor in Apple's new Mac Studio desktop is made using TSMC's 5nm process.

Apple claims the new Mac SoC is made up of 114 billion transistors, the most transistors ever in a PC chip. "Connecting two M1 Max chips with our UltraFusion package architecture enables the chip to scale to new heights never before possible," said Johny Srouji, Apple's senior vice president of hardware technology.

According to industry sources, TSMC is also a major production partner for Apple's UltraFusion package.

Apple is expected to launch a new generation of iPhones and iPads, as well as a new line of Macs, in the second half of 2022, with TSMC as its foundry partner, the sources said. Apple has asked TSMC to use the 4nm process in a series of orders for Apple's next-generation A-series iPhone processors. These orders are equivalent to nearly 150,000 wafers.

In addition, TSMC will also use its 4nm process to manufacture Apple's M2 chips, which will be featured in the new Mac lineup scheduled for the second half of this year. The upcoming iPad will feature Apple Silicon manufactured on TSMC's N3B process, the first Apple device to use foundry 3nm process technology.

Still, according to sources, Apple's shipment outlook this year has turned cautious due to some unfavorable macro factors. The company's iPhone shipments, for example, are only expected to see low-single-digit growth in 2022.