Weak sales of the Acer S3 and Asus Zenbook series Ultrabooks have forced both Acer and Asus to scale back orders by 40%, DigiTimes reported on Thursday. The two companies are said to have slashed orders from between 250,000 and 300,000 units to between 150,000 and 180,000 units. The high-end Ultrabooks, which are priced around $1,000, are not faring well in a PC market that has seen decreased global demand. Sources said to be familiar with Acer’s shipment plans said the company is still confident in Ultrabooks as a whole, and that shipments were on a par with its original expectations. Reportedly, notebook manufacturers are waiting for Microsoft’s new Windows 8 operating system to ship in October, when demand is expected to increase. Intel introduced Ultrabooks in May, and has invested $300 million in the powerful thin and light products that it expects will compete directly with Apple’s MacBook Air. Intel hopes the new products will gain 40% of the global notebook market by the end of 2012.