In March, it became known that the Haswell-chipsets have a problem with their USB 3.0-controllers. After a system with a C1-stepping chipset is restored from standby (S3), the attached USB 3.0-devices are disconnected. Although no data is lost, opened files will have to be reopened.
As soon as the issue was raised, Intel started working on a new revision of the chipsets, but did decide to launch the C1-stepping, reasoning that the majority of consumers wouldn't be affected. The chip manufacturer has now stated that the first C2-stepping motherboards will be available July 29. This revision fixes the issue with the USB controller. Intel will launch its DH87MC, DH87RL, DZ87KLT-75K, DB85FL en DQ87PG and it highly likely that other motherboard manufacturers will follow with their new boards shortly after.
Revision 04 of the southbridge is the C1-stepping with USB 3.0-problems. Revision 05 is the new C2 stepping without the bug