Sometimes it is a good idea to get all the bugs out of the way before investing too much money in a project. Unfortunately for Intel, a bug did slip into the Sandy Bridge P67 chipset in the form of a bad transistor in the controller subsystem (Fig. 1). Sandy Bridge is Intel's 32nm second generation of Core processors (Fig. 2). Intel was up front about the issue in a recent press release (see Intel Identifies Chipset Design Error, Implementing Solution).

Sandy Bridge was being shown with a lot of fanfare at CES 2011. Cost estimates are putting the total expense for Intel at around a billion dollars. That includes $700 million for handling the recall and $300 million in lost sales.

The problem occured in Intel’s 6-series H67/P67 chipsets that has two sets of SATA ports. One set handles four 3 Gbit/s drives and the other works with a pair of 6 Gbit/s drives. The transistor of concern is located in the PLL (phase lock loop) clock tree of the 3 Gbit/s controller. The circuit was biased at too high a voltage for the design and this resulted in an excessively high leakage current. This in turn changes the system's characteristics and causes the controller to fail. The other controller is unaffected as well as it has its own PLL.

It is possible to remove the voltage from the transistor but this is a major board change. Unfortunately a software fix will not work. This is why distributors have stopped shipping motherboards based on these chips.

The problem did not occur in the initial A-stepping chips that were used for design and test. The issue is with the B-stepping chips that were shipped in bulk and found on commercially available motherboards. The updated chip will likely have a C-step or D-step designation.

The problem does not always show up and tends to occur when the system is stressed. Intel found the problem while doing these kinds of tests although not soon enough to prevent many motherboards from being constructed with the bad chip.