Intel C2518 FH8065501516710 Data Sheet

Intel

®

 Atom™ Processor C2000 Product Family for Microserver

Datasheet, Vol. 2 of 3

September 2014

66

Order Number: 330061-002US

The root complex provides primary transaction routing utilizing positive and negative 

decode. Positive decode routing is based on matching attributes between the 

internally-routed transaction and the attached root complex agents. The root complex 

has internal knowledge of its attached agent attributes to enable this decode.

Internal transaction routing is shown in 

Table 4-3

. Transactions not listed in this table 

cause a negative decode. These negative-decode transaction include:

• Lock transaction
• I/O space transaction other than to a root port aperture
• Message transaction with a downstream destination
• Unsupported source-destination pair
• Transaction to disabled memory or I/O region
• Unrecognized transaction type
• Unrecognized address
• Unrecognized ID

The SoC Negative Decode Handler (NDH) mentioned in 

Table 4-3

 sends an 

Unsupported Request (UR) completion on reads and drops writes and completions. 

NDH event error logging occurs.

Memory Space

Base Address Register (BAR)

Any

PCIe* Root Ports

Aperture in Memory Space

Any

PCIe Root Ports

Refetchable Aperture

Any

PCIe Root Ports

Message Signalled Interrupt 

(MSI)

Any

SoC System Agent

HMBound Address

Any

SoC System Agent

Address in the DOS Region

Any

SoC System Agent

I/O Space

Aperture in I/O Space

Any

PCIe Root Ports

Configuration 

Space

Type 0

SoC System Agent PCIe Root Ports, Integrated devices

Type 1 (Bridge)

SoC System Agent PCIe Root Ports

Completion

ID Route

Any

PCIe Root Ports, SoC System Agent

Any

Negative Decode

Any

Integrated Devices

Negative-decode 

transactions that have 

characteristics not capable of 

the integrated devices, such 

as an address width greater 

than 36 bits, or a payload of 

more than 64 bytes, are 

instead sent to the SoC 

Negative Decode Handler 

(NDH).