IBM Power S1112 (9242-21B / 9242-21T)
The entry point into the IBM Power 11 generation: a single-socket, half-width 2U rack or tower system built for branch, edge, and smaller IBM i, AIX, and Linux deployments.
The 9242-21B is the rack form of the IBM Power S1112 and the 9242-21T is the deskside tower form of the same machine. They are the smallest Power 11 systems IBM sells, added to the line in July 2026, a year after the rest of the family. If you are looking up either number you are almost certainly pricing an entry IBM i refresh, because the 4-core build is the only Power 11 configuration that sits in software tier P05.
What makes this machine type worth understanding is the gap between what the platform holds and what IBM i can use on it. The chassis takes 512 GB of memory and 10 cores, but IBM i on the S1112 is bounded at 4 cores and 64 GB with mirrored internal storage. That is not a defect, it is the definition of the machine: a precise fit for a small IBM i footprint, and the wrong box the moment native IBM i growth becomes the real question.
S1112 at a glance
Processor options
S1112 processor feature codes
CPW and rPerf figures are IBM-published relative performance benchmarks, not raw clock speed comparisons. See our CPW and rPerf glossary entries for how to read them.
| Feature Code | Cores | Clock Speed | CPW | rPerf ST | rPerf SMT2 | rPerf SMT4 | rPerf SMT8 | Software Tier |
|---|---|---|---|---|---|---|---|---|
| EJMT | 4-core | 3.6-4.0 GHz | 117,300 | 39.9 | 81.8 | 119.9 | 148.8 | P05 |
| EJSV | 10-core | 3.05-4.0 GHz | 116,500 | 95.4 | 185.6 | 247.0 | 298.7 | P10 |
IBM i on the S1112 is limited to the P05 software tier on the 4-core EJMT (or P10 on the 10-core EJSV), with a hard cap of 4 activated virtual processors and 64 GB of usable memory for IBM i regardless of the physical processor or memory installed. Extra platform memory and cores beyond those IBM i limits (up to 256 GB usable) can still be assigned to AIX, Linux, or VIOS partitions.
Memory, storage, and I/O
Platform configuration limits
| Area | S1112 Detail |
|---|---|
| Memory (physical) | Up to 512 GB DDR5 DDIMM across 4 slots |
| Memory (usable, AIX/Linux/VIOS) | Up to 256 GB |
| Memory (usable, IBM i P05) | Up to 64 GB |
| Internal storage | Up to 12.8 TB raw NVMe U.2 across 4 slots |
| Direct I/O | 4 non-hot-plug PCIe Gen4 slots: 2x x16, 2x x8 |
| Expansion | Can utilize half of a Gen4 I/O expansion drawer when rack-mounted |
| Management | Embedded BMC plus dedicated 1 GbE HMC port; requires HMC v11 (7063-CR2 or vHMC) |
Specs per the IBM Power S1112 9242-21B product listing at Midland Information Systems.
How the S1112 compares to the S1122
S1112 vs S1122
| Question | S1112 | S1122 |
|---|---|---|
| Physical stance | Half-width 2U rack or tower | Full-width 2U rack |
| Processor scale | 4 or 10 cores, 1 socket | Up to 60 cores, 2 sockets |
| Platform memory | Up to 512 GB (64 GB usable for IBM i) | Up to 4 TB |
| IBM i positioning | Entry P05/P10 refresh, small mixed workloads | Broader IBM i growth and denser consolidation |
Choose the S1112 if
You are refreshing an older entry Power system, need a tower option for a smaller server room, or want the smallest current Power 11 footprint for a branch or edge site.
Choose the S1122 instead if
Your IBM i sizing needs more than 4-10 cores or 64 GB of memory, or you need dual-socket scale-out headroom for growth.
IBM 9242-21B datasheet
IBM Power S1112 (9242-21B / 9242-21T) published specifications
| Specification | Value |
|---|---|
| Machine type-model | 9242-21B (rack) / 9242-21T (tower) |
| Generation | IBM Power 11 |
| Sockets | 1 |
| Maximum cores | 10 |
| Memory | 512 GB DDR5 DDIMM platform maximum. 256 GB usable for AIX, Linux and VIOS; 64 GB usable for IBM i at P05 |
| Internal storage | 12.8 TB NVMe U.2 across 4 slots |
| PCIe | 4 non-hot-plug PCIe Gen4 slots: 2x x16, 2x x8 |
| I/O expansion | Can use half of a Gen4 I/O expansion drawer when rack-mounted |
| Management | Embedded BMC plus a dedicated 1 GbE HMC port. Requires HMC v11 on a 7063-CR2 or vHMC |
| Operating systems | IBM i, AIX, Linux, VIOS |
| Software tier | P05 with the EJMT feature, P10 with the EJSV feature |
Figures are the published maximums for this machine type. A specific installed system is defined by its processor feature code and activated core count, not by the machine type alone.
How to confirm you have a 9242-21B
From IBM i
DSPSYSVAL QMODEL returns the model portion and DSPSYSVAL QPRCFEAT returns the processor feature code. Together those two values identify a 9242-21B build exactly, which is more than the S1112 name alone tells a vendor.
From AIX, Linux or VIOS
lsconf reports the machine type and model on the first lines of output. prtconf gives the same alongside processor implementation and clock speed.
From the HMC
Managed system properties shows the machine type-model and serial together, plus installed against activated cores. This is the view to screenshot when requesting a quote.
From the bezel
A 9242-21T is a floor-standing tower and a 9242-21B is a half-width 2U rack unit, so the two are impossible to confuse physically. The full machine type-model and serial are on the label at the front of the chassis.
Next steps for a 9242-21B or 9242-21T
Processor feature codes across the whole family are compared on the Power 11 CPU page, and the full model listing with CPW and rPerf detail is at IBM Power S1112. For configuration ceilings see the Power 11 specs page, for cost drivers see Power 11 pricing, and when you are ready to source one the quote checklist lists what a vendor needs from you.
Sources
- IBM Power 11 Scale-Out Servers Redbook ... IBM Redbooks
Reference Documents
Related
IBM Power S1122 (9824-22A)
A dense, dual-socket 2U scale-out server offering up to 60 Power 11 cores and 4 TB of DDR5 memory, IBM's mainstream choice for growing IBM i, AIX, and Linux environments.
IBM Power L1122 (9856-22H)
The Linux-optimized sibling of the S1122: a dual-socket 2U server with the same hardware ceiling but licensed for Linux-first environments, with limited AIX/IBM i core use.
IBM Power S1124 (9824-42A)
A quad-socket-capable, high-performance 4U scale-out server offering up to 60 Power 11 cores and 8 TB of DDR5 memory, built for enterprises and regional data centers.
IBM Power L1124 (9856-42H)
The Linux-optimized sibling of the S1124: a high-throughput scale-out server for open-source databases and Red Hat OpenShift, with the same DCM processor ceiling as the S1124.
Related Reading
Power 11 S1112 for Healthcare AI: Local Inference and IBM i Continuity
How the IBM Power S1112 fits healthcare AI infrastructure planning when hospitals and health-adjacent teams need compact Power 11 capacity, local inference, and IBM i continuity.
CPW and rPerf Explained: How to Actually Compare Power 11 Processor Options
CPW and rPerf are IBM's relative-performance benchmarks for IBM i and AIX/Linux respectively. Here is how to read them correctly when comparing Power 11 feature codes.
IBM i Licensing and Software Tiers on Power 11: P05, P10, P20, P30 Explained
IBM i software cost on Power 11 is set by the processor feature code's software tier, not the model name. Here is how P05 through P30 map across every current model.
Frequently Asked
What are the IBM Power 11 model numbers?
There are seven current IBM Power 11 models: the entry S1112 (machine type 9242-21B rack, 9242-21T tower), the scale-out S1122 (9824-22A) and S1124 (9824-42A), the Linux-optimized L1122 (9856-22H) and L1124 (9856-42H), and the enterprise scale-up E1150 (9043-MRU) and flagship E1180 (9080-HEU). See our full Power 11 model directory for structured specs on each.
What is the smallest IBM Power 11 model available?
The Power S1112 (9242-21B rack or 9242-21T tower) is the smallest and only current Power 11 model available in a tower form factor, with 4 or 10 processor cores and up to 512 GB of memory.
What PCIe generation does IBM Power 11 use?
Current Power 11 models use direct-chassis PCIe Gen4 slots. The entry S1112 carries 4 non-hot-plug Gen4 slots (2x x16, 2x x8); larger models add capacity through Gen4 I/O expansion drawers rather than a different slot generation. Confirm exact slot count and mix against your target model's spec page before ordering adapters.