If you need AIX UNIX CPU information for troubleshooting, capacity planning, or licensing audits, the fastest route is knowing which AIX commands map to the exact “CPU facts” you care about. AIX exposes CPU data through hardware inventory (lscfg), system configuration (prtconf), and virtualization context (lparstat).
This guide gives you repeatable command recipes and shows how to interpret the outputs so you can answer questions like: How many CPUs are online? What CPU model is installed? Are you capped by an LPAR setting? Is SMT enabled?
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All examples are standard AIX commands you can run on IBM Power Systems. Command output varies a bit by AIX version and firmware level, so focus on the specific fields called out below.
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“CPU information” isn’t one number. On AIX, you might be looking for any of the following:
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- Physical CPU inventory: what the server hardware contains.
- LPAR CPU entitlement and allocation: what your logical partition is allowed to use.
- Online processors: what AIX has brought online.
- Cores vs threads: physical cores and SMT threads (if supported/enabled).
- CPU type/model: Power processor generation and machine attributes.
- Frequency/clock: sometimes reported, sometimes not reliably depending on platform/firmware.
When numbers don’t match across commands, it’s usually because you’re mixing “physical” and “LPAR” views, or you’re comparing cores against threads.
Prerequisites and Where to Run Commands
Most CPU discovery commands are read-only. Still, you’ll get the cleanest results from an account with system access.
Run as a user with sufficient permissions
Try as your normal admin account first. If outputs are incomplete, switch to root (or use sudo) for commands like lsdev and lscfg.
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For compliance or ticket attachments, save command output with timestamps:
# mkdir -p /tmp/cpu_audit_$(date +%Y%m%d_%H%M%S)
# cd /tmp/cpu_audit_$(date +%Y%m%d_%H%M%S)
# ksh
# for c in uname -a prtconf lparstat -i lsattr -El sys0 lscfg -v; do
> $c >> ${c// /_}.txt 2>&1
> done
That way, you can compare after changes like firmware updates or LPAR settings adjustments.
High-Confidence CPU Facts: Use These Core Commands
If you want a quick, reliable baseline, run this set in order and compare the fields. It covers hardware inventory, OS view, and virtualization context.
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lscfg (Hardware inventory)
lscfg is one of the most useful commands for hardware-level CPU details on AIX. The output is detailed but sometimes verbose—filter it to the “processor” class or relevant device tree sections.
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Start with these:
lscfg -vp(list processors/processor-related details)lscfg -l <device_id> -v(when you know a specific processor device name)lscfg -r proc(processor-related devices on some systems/levels)
What to look for:
- Processor model/type fields (often near the top of processor blocks)
- Machine/adapter identifiers depending on platform
- Counts (sometimes core/thread info is present per processor block)
prtconf (System and device tree)
prtconf reports system configuration and device tree information from the kernel/ODM view. Use it for a stable “what AIX thinks exists” perspective.
Common variants:
prtconfprtconf -pv(more verbose)prtconf -v(varies by AIX version; expands processor-related sections)
What to look for:
- CPU/processor entries under the system description
- Hardware platform lines (useful for confirming CPU generation)
lparstat (LPAR vs physical CPU view)
lparstat is the go-to command when you care about virtualization allocation: entitlement, utilization, and processor allocations for the current LPAR.
Run:
lparstatlparstat -i(information-centric output)
What to look for in output (names vary slightly by AIX version):
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- Physical CPUs vs virtual processors (this is the mismatch source)
- Sharing mode (dedicated/shared)
If you’re troubleshooting “why apps see fewer CPUs,” this is typically the command that answers it.
lsattr (Attribute-level CPU details)
lsattr pulls ODM attributes for system devices. For CPU-related attributes, the system device sys0 is a frequent starting point.
Try:
lsattr -El sys0lsattr -E -l sys0(alternate formatting on some releases)
What to look for:
- Attributes that mention processor, sharing, or relevant CPU feature toggles
- Any fields tied to platform CPU behavior and SMT/virtualization (exact attribute names can differ)
If you don’t see anything obviously CPU-specific, it may be because your target attribute isn’t on sys0. Use lsdev first to find relevant device objects.
lsdev (CPU device visibility)
lsdev lists device objects registered in ODM. It’s useful when you suspect AIX isn’t recognizing a processor feature or processor devices are in an unexpected state.
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Start with:
lsdev -Cc processorlsdev -Cc sysplanar(sometimes helps on certain platforms)
Look for device state and class:
- Defined vs Available vs Active (as reported)
- Any “missing” processor-related device objects
Get CPU Counts: Cores, Threads, and Online Processors
Different stakeholders ask for different counts: “How many cores?” “How many CPUs does the OS use?” “How many threads are available with SMT?” AIX can show all of them, but not always via a single command.
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lsmpio / mpstat / psrinfo equivalents on AIX
AIX doesn’t have a single universal psrinfo equivalent like Solaris. However, you can still gather online CPU information using counters from system utilities.
Try these practical checks:
lsdev -Cc processorto confirm processor device objectsps -eLf | wc -lis not a reliable CPU count (process/thread dependent), so avoid it for auditsgetconfqueries (next section) for CPU sizing
getconf and related counters
getconf reads system configuration constants exposed by the OS. Use it to measure what your running kernel reports.
Common commands:
getconf _NPROCESSORS_ONLN(online CPUs as the kernel sees them)getconf _NPROCESSORS_CONF(configured CPUs)
If you see a difference between configured and online, it usually means some CPUs/features are disabled, not present to the OS, or blocked by partition settings.
Checking SMT (Simultaneous Multi-Threading)
SMT changes the relationship between “cores” and “threads.” Some outputs include SMT thread counts, but the most actionable approach is to confirm SMT status and then interpret counts correctly.
On many Power/AIX environments, you can infer SMT configuration by combining:
lparstat -i(LPAR mode and processor configuration)lscfg -vp(processor block details can hint at thread support)- OS-level CPU counts from
getconf
When SMT is enabled, you may observe higher logical processor counts than physical cores. Don’t compare “threads” to “core entitlement” numbers directly—license and scheduling policies may use different units.
Get CPU Model, Platform, and Frequency
Model and generation matter for performance characteristics, microcode/firmware compatibility checks, and vendor support. Frequency is trickier on Power systems; outputs may be approximate or feature-dependent.
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To identify the CPU family/generation reliably, use a combination of OS identity and hardware inventory.
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Try:
uname -a(architecture/OS release context)prtconf | grep -i -E "processor|cpu|model|hardware"(filter noisy output)lscfg -vp(processor blocks usually include model identifiers)
On AIX, “CPU model” lines vary depending on whether you’re in an LPAR and how firmware reports processor identifiers. If the CPU generation matters for support, capture the full processor section from lscfg -vp rather than only grepping one line.
Clock speed and frequency constraints
For frequency, check:
prtconf -pvand scan for frequency or clock fieldslscfg -vpfor any per-processor speed/clock attributes
If you don’t see a clear frequency field, that’s not uncommon—some platforms report clock behavior via performance counters or firmware interfaces instead of static CPU inventory.
In those cases, focus on stable facts (model, cores, SMT/threading, entitlement) and use OS monitoring tools for runtime utilization and effective throughput.
Virtualization and LPAR Gotchas (Why Numbers Don’t Match)
This is the most frequent reason people think their commands are “wrong.” AIX reports what your partition has and is allowed to use, while hardware inventory commands can show physical system details.
- Physical vs LPAR view:
lscfgmay show installed processor inventory, whilelparstatreflects entitlement/allocation. - Cores vs threads: SMT can inflate logical processor counts compared to core counts.
- Online vs configured:
getconf _NPROCESSORS_ONLNcan be less than configured if CPUs aren’t available to the kernel.
If you’re preparing a statement for licensing (or a vendor ticket), include the exact commands used and mention whether the values represent physical CPU capacity or LPAR entitlement.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Aix Commands Cheatsheet (What to Run for What You Need)
| Goal | Command | What you’re hunting |
|---|---|---|
| OS sees how many CPUs | getconf _NPROCESSORS_ONLN |
Online processor count from the running kernel |
| What CPUs the kernel is configured for | getconf _NPROCESSORS_CONF |
Configured processor count (may exceed online) |
| LPAR allocation/entitlement context | lparstat -i |
Sharing mode, entitlement, and allocation constraints |
| Installed processor hardware details | lscfg -vp |
Processor model identifiers, per-processor inventory |
| General system configuration and device tree | prtconf -pv |
CPU/processor sections and platform descriptors |
| CPU-related ODM attributes | lsattr -El sys0 |
System device attributes that affect processor behavior |
| Processor device objects and states | lsdev -Cc processor |
Whether processor devices are available/active |
Troubleshooting: When Commands Show Empty or Confusing Output
If you don’t get the CPU details you expect, try these checks in order.
1) Confirm AIX release and kernel context
Different AIX levels output different fields. Run:
oslevel -runame -m
2) Use verbose hardware inventory
If lscfg -vp is too short, increase visibility:
lscfg -vp | moreprtconf -pv | more- Capture full processor blocks instead of grepping one line
3) Check for LPAR limits causing mismatches
If OS-visible CPUs are lower than physical counts, trust lparstat -i for entitlement/allocation. For example, licensing tools may count only entitled processors, while inventory reports physical cores.
4) Validate CPU device objects
If lsdev -Cc processor shows unexpected state or missing devices, it can indicate configuration drift, partial boot, or ODM inconsistencies.
- Verify expected processor device class exists
- Re-check with root privileges
- Confirm the system is fully booted and not in a maintenance state
5) Treat frequency as optional (unless your platform reports it)
When frequency isn’t present, don’t force it. Use runtime metrics instead of static frequency lines, and keep your CPU model and entitlement evidence for vendor escalation.
FAQ
Which command is best for a quick answer: online CPU count or CPU model?
For “how many CPUs does AIX use right now,” use getconf _NPROCESSORS_ONLN. For CPU model/generation, use lscfg -vp (and back it with prtconf -pv).
Why does lscfg show more processors than getconf?
That’s usually because lscfg reflects physical installed inventory, while getconf reflects what the kernel sees in the current LPAR and online state.
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How do I confirm SMT settings on AIX?
Use a combination of lparstat -i and processor details from lscfg -vp, then reconcile with logical/online counts from getconf. SMT affects how you interpret cores vs logical CPUs.
What should I include in a ticket to IBM or a vendor?
Include command outputs from oslevel -r, lparstat -i, getconf _NPROCESSORS_ONLN, and the processor sections from lscfg -vp or prtconf -pv.
Bottom Line
To find AIX UNIX CPU information reliably, separate “hardware inventory” (use lscfg -vp and prtconf -pv) from “LPAR entitlement/allocation” (use lparstat -i) and from “what the kernel is using now” (use getconf _NPROCESSORS_ONLN).
With that three-way split, the outputs stop contradicting each other—and you can produce numbers that match what licensing, monitoring, and vendor support teams expect.
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