SemiAccurate appears to have uncovered reports of a potentially serious issue with certain Asustek Computer motherboards that could leave customers seeing their boards fail sooner than expected, and may even cause damage to other system components such as the CPU.
Tipped off by reports in various user forums, SemiAccurate's says that motherboard owners are discovering what looks to be rusted chokes on their boards. The boards include those that are new, or released within the past year or so.
Chokes, the usually square component found clustered around the CPU socket and sometimes other parts of a motherboard, act as a "short-term storage area" for electrical charge as it passes from the MOSFETs to the capacitors and onto the CPU. Good quality chokes are able to hold a higher charge for longer meaning the MOSFETs can switch off more frequently.
On the other hand, old, damaged or degraded chokes are unable to retain their charge which forces the MOSFETs to open more frequently. This causes the system to draw more power, reducing the overall efficiency of the motherboard while producing more heat, and increases the workload of other components – the MOSFETs, capacitors, and PSU – which over time could eventually lead to these parts failing also. The result is a dead motherboard or PSU, and if the user is unlucky, whatever component lies beyond the capacitors, usually the CPU, could also get damaged.
High-quality chokes are made from ferrite, which doesn't rust, while motherboard makers may use cheaper chokes made from iron in their low-end and mid-range boards to reduce costs. This suggests that owners of Asustek's high-end boards aren't likely to be affected by this issue, but that still leaves the cheaper (i.e. the high-volume) segments potentially exposed, meaning Asustek could face a large number of RMA cases down the road.
It's possible for rusting as seen in SemiAccurate's images to be caused by water or condensation which accumulated on the boards sometime after they shipped from Asustek. However, such cases are usually isolated (the result of end-user error) or in regions known for high humidity, such as near the coast.
But since current reports are coming from users as far apart as Taiwan and Singapore, and include claims of brand-new off-the-shelf boards already showing signs of corrosion, it's much more likely that the problem originated somewhere within Asustek's supply chain, most likely during the production of the chokes themselves.
A followup post by SemiAccurate in which the site opened up some of the affected chokes and discovered that the corrosion is not just on the surface of the components, and in fact extends right through to the core appears to back the hypothesis that the issue arose at some point during the manufacturing of the chokes, possibly by contamination, or that the parts were not allowed to dry thoroughly.
Despite it being almost a week since SemiAccurate first publicized the claims, Asustek has not yet acknowledged the reports or contacted the site. Asustek did acknowledge receipt of our email inquiries, but said the relevant spokesperson was currently unavailable and would get back to as soon as possible. We will continue to update this story as it develops.
Update: A representative for Asustek in Taiwan has responded saying there have been no reported cases of anomalous motherboard behavior resulting from the alleged rusty chokes issue to date. The company added is saying, "We are unable to comment on the specific article published on SemiAccurate, as no one from the site has approached us for clarification." The company finished in saying that its service center engineers are happy to assist customers with any questions or concerns.
SemiAccurate maintains that it did reach out to Asustek's offices in the US with no response.
Chokes showing apparent rust corrosion
Photo: SemiAccurate, used with permission