Datasheet

PCI Express Non-Transparent Bridge
Intel
®
Xeon
®
Processor C5500/C3500 Series
Datasheet, Volume 1 February 2010
146 Order Number: 323103-001
Enumeration software can determine how much address space the device requires by
writing a value of all 1's to the BAR and then reading the value back. Unimplemented
Base Address registers are hardwired to zero.
The size of each BAR is determined based on the weight of the least significant bit that
is writable in the BAR address bits b[63:7] for a 64b BAR. (The minimum memory
address range defined in PCIE is 4KB). Table 80 shows the possible memory size that
can be specified by the BAR.
Note: Programming a value of ‘0’ or any other value other than (12-39) into any of the size
registers (PBAR23SZ, PBAR45SZ, SBAR23SZ, SBAR45SZ)will result in the associated
BAR being disabled.
The NTB accepts only those configuration and memory transactions that are addressed
to the bridge. It must return an unsupported request (UR) response to all other
Configuration Register transactions.
3.6.1 “A Priori” Configuration Knowledge
The PCIE x4/x8 port 0 is capable of operating as a RP, NTB/RP or NTB/NTB. The chipset
cannot dynamically make these determinations upon power up so this information must
be provided by BIOS prior to enumeration.
3.6.2 Power On Sequence for RP and NTB
Intel
®
Xeon
®
processor C5500/C3500 series systems and connecting devices/systems
through the RP/NTB will likely be cycled on at different times. The following sections
describe the power-on sequence and its impact to enumeration.
3.6.3 Crosslink Configuration
Crosslink configuration is required whenever two like PCIE ports are connected
together. E.g. two downstream ports or two upstream ports.
Crosslink configuration is also only required when the PCIE port is configured as back to
back NTB’s. Hardware will resolve RP and NTB/RP cases based on PPD Port definition.
Table 80. Memory Aperture Size Defined by BAR
least significant
bit set to 1
Size of Memory Block
11 2KB
12 4KB
13 8KB
... ...
32 4GB
33 8GB
34 16GB
35 32GB
36 64GB
37 128GB
38 256GB
39 512GB