IBM i series Handbook page 302

Towers and Racks
The external xSeries server has SPCN control. SPCN cabling for the external xseries server
follows the same rules as SPCN cabling for existing HSL attached towers.
The external xSeries server attaches to a Model 270 or Model 8xx server via a copper HSL
(optical HSL is not supported). The external xSeries server does not count against the
current limits of HSL towers on a per loop, or per system basis except on the Model 840. The
840 has a system tower limit that cannot support the maximum number of I/O towers in
addition to the maximum number of external xSeries servers. The Model 840 has a system
limit of 47 total towers.
The maximum external xSeries servers by model (these maximums are in addition to the
maximum number of I/O towers that can attach to these models) are:
• Model 270 - System maximum is 2
• Model 820 - System maximum is 4
• Model 830 - System maximum is 8
• Model 840 - System maximum is 16
The maximum external xSeries servers per HSL loop by model are:
• Model 270 - Maximum per loop is 2
• Model 820 - Maximum per loop is 4 (system limit)
• Model 830 - Maximum per loop is 5 (limit on first loop is one)
• Model 840 - Maximum per loop is 5 (limit on first loop is five)
These maximums are in addition to the maximum number of I/O towers that can attach per
HSL loop to these models.
For performance and stability reasons, place the external xSeries server in the middle of an
HSL loop on HSL loops without switched towers. That is, the end of the HSL strings attach to
each HSL port. No I/O tower should communicate with the system by having its data flow
through an external xSeries server. Switched towers are required to be adjacent to a tower
owned by the alternate system. If an external xSeries server must be on a loop with a
switched tower, place the external xSeries server so it does not communicate with the system
through a private tower.
Each external xSeries server is independent of the number of internal Integrated xSeries
Servers and Integrated Netfinity Servers.
For further information, refer to the AS/400e to iSeries Migration redbook, SG24-6055.
The latest information on which xSeries or Netfinity Servers can be ordered is contained on
the xSeries server Web site:
272
iSeries Handbook
http://www.iseries.ibm.com/windowsintegration/