Datasheet

PCI Express Non-Transparent Bridge
Intel
®
Xeon
®
Processor C5500/C3500 Series
Datasheet, Volume 1 February 2010
152 Order Number: 323103-001
3.6.6 Address Translation
The NTB uses the BARs in the Type 0 configuration header specified above to define
apertures into the memory space on the other side of the NTB. The NTB supports two
sets of BARs, one on the local host interface and the other on the remote host
interface.
Each BAR has control and setup registers that are writable from the other side of the
bridge. The address translation register defines the address translation scheme. The
limit register is used to restrict the aperture size. These registers must be programmed
prior to allowing access from the remote subsystem.
3.6.6.1 Direct Address Translation
The Intel
®
Xeon
®
processor C5500/C3500 series NTB supports two Direct Address
Translation windows both inbound and outbound. These are BAR 2/3 and BAR 4/5.
Direct address translation is used to map one host address space into another host
address space. The NTB is the mechanism used to connect the two host domains and
translates all transactions sent across the NTB both inbound and outbound. This means
all transactions traversing from the secondary side of the NTB to the primary side of the
NTB are translated and all transactions traversing from the primary side of the NTB to
the secondary side of the NTB are translated.
Figure 55. Intel
®
Xeon
®
Processor C5500/C3500 Series NTB Port - BARs
SBAR 4/5
Window
Lo
Con
Par
cal
fig
ms
System
Memory
Map
System
Memory
Map
Primary Secondary
Cfg
Space
PBAR 0/1
PBAR 2/3
PBAR 4/5
PBAR 2/3
Window
PBAR 4/5
Window
Secondary
Memory
Window 2
Secondary
Memory
Window 1
CPU/
DMA
Cfg
Space
SBAR 0/1
SBAR 2/3
SBAR 4/5
Secondary
BAR2/3
Xlate
Secondary
BAR4/5
Xlate
Intel® Xeon® Processor C5500/C3500 Series System
CPU/
DMA
Remote System
Primary
Memory
Window 1
Primary
Memory
Window 2
0
Primary BAR4/5 Xlate Base
Primary BAR2/3 Xlate Base
Secondary BAR4/5 Xlate Base
Secondary BAR2/3 Xlate Base
SBAR 2/3
Window
Primary
BAR4/5
Xlate
Primary
BAR 2/3
Xlate