Chipset; Overview; I/O Hub; Quickpath Interconnect - Dell PowerEdge M610x Technical Manual

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8 Chipset

8.1 Overview

The Dell™ PowerEdge™ M610x system board incorporates the Intel 5500 chipset for I/O and processor
interfacing which was designed to support Intel Xeon Processor 5500 and 5600 Series, QuickPath
Interconnect, DDR3 memory technology, and PCI Express Generation 2. The chipset consists of the
I/O Hub (IOH) and Intel I/O Controller Hub 9 (ICH9).

8.2 I/O Hub

The M610x system board uses the Intel 5520 chipset 24D I/O hub (IOH) to provide a link between the
processor(s) and I/O components. The main components of the IOH consist of two full-width
QuickPath Interconnect links (one to each processor), 24 lanes of PCI Express Gen2, a x4 Direct Media
Interface (DMI), and an integrated IOxAPIC.
8.2.1

QuickPath Interconnect

The QuickPath Interconnect (QPI) architecture consists of serial point-to-point interconnects for the
processors and the IOH. The M610x has a total of three QPI links: one link connecting the processors
and two links connecting both processors with the IOH. Each link consists of 20 lanes (full-width) in
each direction with a link speed of 6.4 GT/s. An additional lane is reserved for a forwarded clock.
Data is sent over the QPI links as packets.
The QuickPath architecture implemented in the IOH and CPUs features four layers. The Physical layer
consists of the actual connection between components. It supports Polarity Inversion and Lane
Reversal for optimizing component placement and routing. The Link layer is responsible for flow
control and the reliable transmission of data. The Routing layer is responsible for the routing of QPI
data packets. Finally, the Protocol layer is responsible for high-level protocol communications,
including the implementation of a MESIF (Modify, Exclusive, Shared, Invalid, Forward) cache
coherence protocol.
8.2.2

PCI Express

PCI Express (PCIe) is a serial point-to-point interconnect for I/O devices. PCIe Generation 2 doubles
the signaling bit rate of Generation 1 from 2.5 Gb/s to 5 Gb/s. Each of the PCIe Gen2 ports are
backward-compatible with Gen1 transfer rates.
The IOH 24D has 24 PCI Express lanes. The lanes are partitioned as two x2 ports and combined as a x4
PCI Express Gen2 port for the LOM1. The next port is a x4 PCI Express Gen2 port for LOM2 and the
remaining x4 ports are combined as two x8 PCI Express Gen2 ports for the mezzanine cards. These
last two x8 Gen2 ports are the entities that provide communication for the M610x functionality.
8.2.3

Direct Media Interface

The Direct Media Interface (DMI) connects the IOH with the Intel I/O Controller Hub 9 (ICH9). The
DMI is equivalent to a x4 PCIe Gen1 link with a transfer rate of 1 GB/s in each direction.
8.2.4

I/O Controller Hub 9

The I/O Controller Hub 9 (ICH9) is a highly integrated I/O controller, supporting the following
functions:

Six x1 PCI Express Gen1 ports, with the capability of combining ports 1-4 as a x4 link (The x4 link
is routed to the storage controller card connector.)
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