IBM i Rack, Power, and Cooling Infrastructure

Will a new server actually fit in our existing rack?

Not always. Power server depth and weight requirements vary by generation, and older racks sized for previous hardware generations do not always accommodate current models cleanly without a rail kit mismatch or clearance issue.

Buyers planning a server refresh should confirm rack depth, rail kit compatibility, and floor loading capacity as part of the same project, rather than discovering a mismatch after the new hardware arrives.

What AS400 power requirements should we check before a hardware refresh?

Check the exact machine type, power supply configuration, rack depth, PDU capacity, UPS runtime, cooling capacity, and service clearance for the final configuration, not a generic platform label.

Power requirements matter before ordering because facilities work can delay a server deployment even when the hardware is available. The safest process is to review the final hardware quote with the facilities or data center team before committing to the migration timeline.

Who should sign off AS400 facilities readiness before a cutover?

The people who own the room and workload should sign off before the cutover.

• IT
• Facilities or data center staff
• Installer or reseller
• Workload owner
• Rack
• Power
• UPS
• PDU
• Cooling
• Cabling
• HMC
• Console
• Service-clearance plan

The sign-off should use the final configured system, not a generic model estimate. If the configuration changes after review, repeat the facilities check.

How much power does an AS400 server actually draw?

Far less than its rating. IBM publishes two different numbers for the same machine and they are not close.

The rated maximum is what the machine is permitted to pull, and it is the figure an electrician and an inspector work from. The measured figure comes from IBM's own filings under EU Regulation 2019/424, where IBM tests a high-end and a low-end configuration of each machine type and reports idle and maximum power for both.

Across the Power 9 family the measured maximum runs between 22 and 55 percent of the rated maximum. A two-socket Power S924 rated at 2,750 W measures just under 965 W flat out. A Power S914 rated at 1,600 W measures 350.5 W.

The practical rule that follows:

• Size the circuit to the rated maximum, because that is what codes and inspection require.
• Size the UPS and the cooling budget to the measured maximum plus a real margin, because sizing those to the rating buys capacity the machine will never ask for.
• Get your own measurement from a metered rack PDU once the machine is installed, because your configuration decides where inside the tested range it actually sits.

How many watts does each IBM Power generation need?

It depends far more on the machine type than the generation. Within a single generation the spread can be enormous, and the entry machines have been getting smaller while the enterprise machines have grown.

Rated maximum power for the entry model of each generation:

• Power 5, eServer i5 520 (9406-520): 750 W
• Power 6, Power 520 (8203-E4A): 770 W
• Power 7, Power 720 (8202-E4B): 750 W
• Power 8, Power S812 (8284-21A): 1,225 W
• Power 9, Power S914 (9009-41A): 1,600 W
• Power 10, Power S1014 (9105-41B): 1,075 W
• Power 11, Power S1112 (9242-21B): 550 W

Rated maximum power for the 4U scale-out model of each recent generation:

• Power 8, Power S824 (8286-42A): 2,300 W
• Power 9, Power S924 (9009-42A): 2,750 W
• Power 10, Power S1024 (9105-42A): 2,750 W
• Power 11, Power S1124 (9824-42A): 2,950 W

The enterprise machines publish per node rather than per system. A Power 9 E980 node is 4,130 W, a Power 10 E1080 node is 4,500 W and a Power 11 E1180 node is 4,850 W, and a fully populated system holds four of them plus a system control unit.

The oldest machines are the outliers in the other direction. A Power 5 eServer i5 595 (9406-595) is a three-phase 19.4 kW frame, which is as much as four Power 11 E1180 nodes.

How much cooling does an IBM Power server need?

Work from the thermal output IBM publishes for the machine type, then divide by 12,000 BTU per hour, which is one ton of refrigeration.

Maximum thermal output by machine type:

• Power S1112 (9242-21B): 1,877 BTU/hr, about 0.16 tons
• Power S914 (9009-41A): 5,461 BTU/hr, about 0.46 tons
• Power S922 (9009-22A): 6,416 BTU/hr, about 0.53 tons
• Power S924 (9009-42A): 9,386 BTU/hr, about 0.78 tons
• Power S1024 (9105-42A): 9,383 BTU/hr, about 0.78 tons
• Power S1124 (9824-42A): 10,065 BTU/hr, about 0.84 tons
• Power E950 (9040-MR9): 14,403 BTU/hr, about 1.2 tons
• Power E1080 node (9080-HEX): 15,355 BTU/hr, about 1.28 tons
• Power E1050 (9043-MRX): 16,889 BTU/hr, about 1.41 tons
• Power E1180 node (9080-HEU): 16,548 BTU/hr, about 1.38 tons
• Power E1150 (9043-MRU): 18,245 BTU/hr, about 1.52 tons

A single 4U scale-out machine is most of a ton on its own. Four of them in a rack is a three to three and a half ton problem before storage, networking, or the HMC are counted, and a four-node enterprise system runs to five and a half tons.

These are rated ceilings rather than steady-state loads, so a room built entirely to them will be over-provisioned. They are the right basis for the worst case, and the measured figures are the right basis for the day-to-day one.

Does a newer Power server need more electrical capacity than the one it replaces?

Usually less, and often much less. This surprises buyers who assume a newer machine must be hungrier.

The entry class has fallen sharply across three generations. A Power 9 S914 is rated at 1,600 W, the Power 10 S1014 that replaces it at 1,075 W, and the Power 11 S1112 at 550 W. That is roughly a third of the load in two generations, and the S1112 will run on a standard 120 V circuit where the S914 usually did not.

The scale-out class is broadly flat. A Power 9 S924 and a Power 10 S1024 carry the same 2,750 W rating and the same 4U footprint, and the Power 11 S1124 is 2,950 W. The rating barely moves while the work done inside it rises considerably.

The multi-drawer legacy machines are where the saving is largest. A 32-core Power 6 Power 570 is four stacked drawers at 5,600 W across 16 rack units and roughly 254 kg. A Power 11 S1124 replaces it in 4U at 2,950 W, which removes twelve rack units, about 210 kg and roughly half the electrical load.

The exception is the midrange four-socket line, which has grown each generation: E950 at 4,220 W, E1050 at 4,950 W, E1150 at 5,400 W. If you are moving up into that class rather than across, plan for more capacity rather than less.

What voltage does an IBM Power server need?

Most of them require 200 to 240 V ac, single phase, at 50 or 60 Hz. Only a small set of entry machines will accept a 100 to 127 V circuit, and getting this wrong is the most common electrical surprise in a hardware refresh.

Machine types that accept 100 to 127 V ac:

• Power S1112 (9242-21B and 9242-21T), Power 11
• Power S1014 (9105-41B) with 1200 W power supplies, Power 10
• Power S1022, S1022s and L1022 (9105-22A, 9105-22B, 9786-22H), Power 10
• Power S914 (9009-41A and 9009-41G), Power 9
• Power S812, S812L, S814 and S824 with 900 W supplies (8284-21A, 8247-21L, 8286-41A, 8286-42A), Power 8
• Power 720 (8202-E4B, E4C, E4D), Power 7
• Power 520 and Power 550 (8203-E4A, 8204-E8A, 9407-M15, 9408-M25, 9409-M50), Power 6

Everything else in the Power line requires 200 V or better. Two cases deserve extra care. On Power 8 the power supply feature decides the answer, so two machines with the same machine type can have different requirements, and the supply feature code needs to be confirmed in writing before a relocation. On the oldest enterprise frames the requirement is three phase entirely: a Power 5 eServer i5 595 takes 200 to 240, 380 to 415 or 480 V ac at three phase, and cannot be moved into a room wired for single-phase equipment whatever the rack space suggests.