The majority of Acer's tablet orders returned back into the hand of Quanta Computer, which landed 60% of Acer's orders in the first half of the year, according to sources from the upstream supply chain. Quanta declined to comment about its orders, but said it will continue to focus on profits instead of pushing volumes.

With their advantages in costs, China's component suppliers and ODMs are gradually penetrating into the supply chain of Taiwan-based vendors, causing Taiwan makers to lose their orders.

Vendors such as Acer and Hewlett-Packard (HP) had both been increasing their tablet outsourcing to China-based makers to improve their costs.

With Quanta's quotes gradually approaching the level of China-based makers, Acer started shifting its orders back to Quanta at the end of the first quarter and the early second quarter, allowing the Taiwan-based ODM to become the largest tablet supplier of Acer, the sources said.

The sources also pointed out that China makers' quotes are lower, but Taiwan makers have better manufacturing ability. Quanta's automated production lines also helped the company to land orders from Acer.

Acer's remaining 40% orders are shared by two China-based makers.