Production of a new 21-inch iMac featuring a 4096 by 2304 screen kicked off in early September and will be launched in the fourth quarter, with shipments in the quarter estimated at 1.4-1.5 million units, according to Taiwan-based supply chain makers.

With shipments from existing iMac products, Apple's overall all-in-one PC shipments could surpass those of Lenovo in the second half.

The sources pointed out that the new 21-inch iMac only has a limited change in industrial design, but is upgraded with better hardware specifications, especially the Ultra HD display.

Currently, Apple is able to ship about four million iMacs each year, about the same as Lenovo, but iMacs have a much higher ASP. Apple's lowest-end iMac is priced starting at US$1,099, while Lenovo's high-end all-in-one PCs start at the same price point. Lenovo's mid-range and entry-level models are priced starting US$599.99 and US$399,99, respectively.

Worldwide all-in-one PC sales have started recovering recently mainly thanks to strong demand from Internet cafes and industrial applications mainly in China.