The PCH controls certain data paths and support functions used in conjunction with Intel CPUs. These include clocking (the system clock), Flexible Display Interface (FDI) and Direct Media Interface (DMI), although FDI is only used when the chipset is required to support a processor with integrated graphics. As such, I/O functions are reassigned between this new central hub and the CPU compared to the previous architecture: some northbridge functions, the memory controller and PCI-e lanes, were integrated into the CPU while the PCH took over the remaining functions in addition to the traditional roles of the southbridge.
The PCH architecture supersedes Intel's previous Hub Architecture, with its design addressing the eventual problematic performance bottleneck between the processor and the motherboard. Over time, the speed of CPUs kept increasing but the bandwidth of the front-side bus (FSB) (connection between the CPU and the motherboard) did not, resulting in a performance bottleneck.
Under the Hub Architecture, a motherboard would have a two piece chipset consisting of a northbridge chip and a southbridge chip. As a solution to the bottleneck, several functions belonging to the traditional northbridge and southbridge chipsets were rearranged. The northbridge is now eliminated completely and its functions, the memory controller and PCI Express lanes for expansion cards, are now incorporated into the CPU die or package.
The PCH then incorporates a few of the remaining northbridge functions (e.g. clocking) in addition to all of the southbridge's functions. The system clock was previously a connection and is now fused in with the PCH. Two different connections exist between the PCH and the CPU: Flexible Display Interface (FDI) and Direct Media Interface (DMI). The FDI is only used when the chipset requires supporting a processor with integrated graphics. The Intel Management Engine was also moved to the PCH starting with the Nehalem processors and 5-Series chipsets.
With the northbridge functions integrated to the CPU, much of the bandwidth needed for chipsets is now relieved.
This style began in Nehalem and will remain for the foreseeable future, through Cannonlake.
Beginning with ultra-low-power Broadwells and continuing with mobile Skylake processors, Intel incorporated the clock, PCI controller, and southbridge IO controllers into the CPU package, eliminating the PCH for a system on a chip (SOC) design. Rather than DMI, these SOCs directly expose PCIe lanes, as well as SATA, USB, and HDA lines from integrated controllers, and SPI/I²C/UART/GPIO lines for sensors. Like PCH-compatible CPUs, they continue to expose DisplayPort, RAM, and SMBus lines. However, a fully integrated voltage regulator will be absent until Cannonlake.
Bogus USB ports will be detected by desktop PCHs equipped with 6 USB ports (3420, H55) on the first EHCI controller. This can happen when AC power is removed after entering ACPI S4. Applying AC power back and resuming from S4 may result in non detected or even non functioning USB device (erratum 12)
Bogus USB ports will be detected by mobile PCH equipped with 6 USB ports (HM55) on the first EHCI controller. This can happen when AC power and battery are removed after entering ACPI S4. Applying AC power or battery back and resuming from S4 may result in non detected or even non functioning USB device (erratum 13)
Reading the HPET comparator timer immediately after a write returns the old value (erratum 14)
SATA 6Gbit/s devices may not be detected at cold boot or after ACPI S3, S4 resume (erratum 21)
This section's factual accuracy may be compromised due to out-of-date information. Please update this article to reflect recent events or newly available information.(December 2012)
In the first month after Cougar Point's release, January 2011, Intel posted a press release stating a design error had been discovered. Specifically, a transistor in the 3 Gbit/s PLL clocking tree was receiving too high voltage. The projected result was a 5–15% failure rate within three years of 3 Gbit/s SATA ports, commonly used for storage devices such as hard drives and optical drives. Through OEMs, Intel plans to repair or replace all affected products at a cost of $700 million.
Patsburg is the codename of a PCH in Intel 7 Series chipsets for server and workstation using the LGA 2011 socket. It was initially launched in 2011 as part of Intel X79 for the desktop enthusiast Sandy Bridge-E processors in Waimea Bay platforms. Patsburg was then used for the Sandy Bridge-EP server platform (the platform was codenamed Romley and the CPUs codenamed Jaketown, and finally branded as Xeon E5-2600 series) launched in early 2012.
Launched in the fall of 2013, the Ivy Bridge-E/EP processors (the latter branded as Xeon E5-2600 v2 series) also work with Patsburg, typically with a BIOS update.
A design flaw causes devices connected to the Lynx Point's integrated USB 3.0 controller to be disconnected when the system wakes up from the S3 state (Suspend to RAM), forcing the USB devices to be reconnected although no data is lost. This issue is corrected in C2 stepping level of the Lynx Point chipset.