Many of the Windows PC makers building ultraportable notebooks based on Intel's low-cost CULV platform are learning first-hand that their cheaper case designs aren't enough to sustain the systems, a research note from AmTech analyst Doug Freedman says. Many of the companies design the systems with plastic shells to keep their prices down but are discovering that the cases are cracking, often forcing major replacements. Which companies are affected aren't mentioned, but Lenovo and MSI are some of the first making systems in the category with the IdeaPad U350 and X-Slim line respectively.

The problem is endemic enough that the contractors tasked with assembling the systems are urging the designers to switch to metal shells to maintain their build quality. Plastic design techniques that have worked for trimming prices on netbooks and full-size netbooks are now believed to be ineffective.

"Cost-reduction features are going to be hard in that form factor on the industrial design side," Freedman says.

The discovery partly validates approaches embraced by companies like Apple and Dell, whose respective MacBook Air and Adamo systems are more expensive partly due to their uses of aluminum casing that maintains the rigidity of the system while simultaneously allowing even thinner cases than most CULV systems and using faster if more expensive components.

Intel for its part has told CNET that the the CULV platform itself isn't at the heart of the issue and that it's the designs framing the processor and mainboard that cause the failures.