IBM Power 780 Technical Overview And Introduction page 105

General rule for the 12X I/O drawer configuration
To optimize performance and distribute workload, use as many multiple GX++ buses as
possible. Figure 2-30 shows several examples of a 12X I/O drawer configuration.
770
780
770
780
One I/O Drawer
770
780
770
780
Two I/O Drawers
Figure 2-30 12X I/O Drawer configuration
Supported 12X cable length for PCI-DDR 12X Expansion Drawer
Each drawer requires one Dual Port PCI DDR 12X Channel Adapter, either short run
(FC 6446 CCIN 520B) or long run (FC 6457 CCIN 520A). The choice of adapters depends on
the distance to the next 12X channel connection in the loop, either to another I/O drawer or to
the system unit. Table 2-26 identifies the supported cable lengths for each 12X channel
adapter. I/O drawers that contains the short range adapter can be mixed in a single loop with
I/O drawers that contain the long range adapter. In Table 2-26, a value of Yes indicates that
the 12X cable identified in that column can be used to connect the drawer configuration
identified to the left. A value of No means that it cannot be used.
Table 2-26 Supported 12X cable lengths
Connection type
FC 5796 to FC 5796 with FC 6446 in both drawers
FC 5796 with FC 6446 adapter to FC 5796 with FC 6457
adapter
FC 5796 to FC 5796 with FC 6457 adapter in both drawers
FC 5796 with FC 6446 adapter to system unit
FC 5796 with FC 6457 adapter to system unit
770
PCIe
780
770
780
Three I/O Drawers
770
780
PCIe
770
PCIe 780
Four I/O Drawers
Chapter 2. Architecture and technical overview
PCIe
PCIe
PCIe
PCIe
PCI-X
PCIe
PCIe
12X cable options
0.6 m 1.5 m 3.0 m
Yes Yes No
Yes Yes Yes
Yes Yes Yes
No Yes Yes
No Yes Yes
8.0 m
No
No
Yes
No
Yes
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