Optimal performance guidelines for PCI adapters

For optimal adapter performance, use the following general placement guidelines, which are for adapters that are moderately to highly active.

POWER6 system units and the 5796 expansion unit

• The POWER6™ system units and 5796 expansion unit do not contain multi-adapter bridge slots but instead have direct host bridge slots, which can increase performance.
• Place high-bandwidth and extra-high bandwidth PCI-X DDR adapters in the PCI-X DDR slots in the system first, and then the PCI-X DDR slots in the expansion unit.
• Place PCIe adapters in PCIe slots only. For more information, see PCI Express.
• Limit to 2 the number of extra-high bandwidth adapters per PCI host bridge (PHB).
• Limit to 3 the number of high bandwidth adapters per PHB.
• Spread out high-bandwidth and extra-high bandwidth adapters across towers or drawers and HSL, HSL-2, or 12X loops. Place the towers or drawers with the most high-bandwidth and extra-high bandwidth adapters closest to the system unit on the HSL, HSL-2, or 12X loops.
• When more then 50% of a loop is used for the AIX® operating system, follow the System p® configuration rules for that loop. One of these rules is to limit the number of I/O expansion units to 4 per loop. For more information about these rules, see the PCI adapter placement for machine types 82xx and 91xx. For model 9406-MMA, see the rules for model 9117-MMA. For models 9407-M15 and 9408-M25, see the rules for model 8203-E4A. For model 9409-M50, see the rules for model 8204-E8A.

5088, 0588, 5094, 5096, 5294, 5296, 8294, 9194, 0595, 5095, or 5790 expansion unit

• Place high-bandwidth and extra-high bandwidth PCI-X adapters in the PCI-X slots in the expansion units.
• Limit to 1 the number of extra-high performance adapter per multi-adapter bridge, with no other extra-high performance adapters on the same multi-adapter bridge. PCI bridges for all the systems and expansion units covered in this publication are identified in Configuration tables for system units and expansion units.
• Limit to 2 the number of high-bandwidth adapters per multi-adapter bridge with no other extra-high bandwidth adapters in the same multi-adapter bridge.
• Spread out high-bandwidth and extra-high bandwidth adapters across multi-adapter bridges, towers or drawers and HSL, HSL-2, or 12X loops. Place the towers or drawers with the most high-bandwidth and extra-high bandwidth adapters closest to the system unit on the HSL, HSL-2, or 12X loops.
• When more then 50% of a loop is used for the AIX operating system, follow the System p configuration rules for that loop. One of these rules is to limit the number of I/O expansion units to 4 per loop. For more information about these rules, see the PCI adapter placement for machine types 82xx and 91xx. For model 9406-MMA, see the rules for model 9117-MMA. For models 9407-M15 and 9408-M25, see the rules for model 8203-E4A. For model 9409-M50, see the rules for model 8204-E8A.
• For more information about optimizing performance, see the Performance Capabilities Reference publications at http://www-03.ibm.com/servers/eserver/iseries/perfmgmt/resource.html.