Datasheet
Intel
®
Xeon
®
Processor C5500/C3500 Series
February 2010 Datasheet, Volume 1
Order Number: 323103-001 137
PCI Express Non-Transparent Bridge
In contrast, a NTB provides logical isolation of resources in a system in addition to
providing electrical isolation and system expansion capability. The NTB connects a local
subsystem to a remote subsystem and provides isolation of memory space between the
two subsystems. The local host discovers and enumerates all local Endpoint devices
connected to the system. The NTB is discovered by the local host as a Root Complex
Integrated Endpoint (RCiEP), the NTB then exposes its CSRs with Type 0 header to the
local host. The local host stops enumeration beyond the NTB and marks the NTB as a
logical Endpoint in its memory space. Similarly, the remote host discovers and
enumerates all the Endpoint devices connected to it (directly or through TBs). When
the remote host discovers the NTB, the NTB exposes a CSR with Type 0 header on the
remote interface as well. Thus the NTB functions as an Endpoint to both domains,
terminates the enumeration process from each side and isolates the two domains from
each other.
Figure 46. Enumeration in System with Transparent Bridges and Endpoint Devices
CPU
Transparent
Bridge
Type 1
Transparent
Bridge
Type 1
Transparent
Bridge
Type 1
End
Point
End
Point
End
Point
End
Point
Type 0