Big idea first (this matters) …
The AS/400 (now IBM i on Power Systems) was never about raw GHz or core counts. Its performance model is based on :
- Tightly integrated hardware and Operating System
- Specialized instruction sets
- Workload-oriented benchmarks, not generic ones
So if you compare it directly to x86 servers on specs alone, you’ll get wildly misleading conclusions. Here is the evolution of AS/400 processors …
From 1988 to 1994 : CISC-era AS/400
Processors :
- Custom 48-bit CISC processors designed by IBM (called “IMPI”)
- Not compatible with any other architecture
Key traits :
- Extremely advanced for their time
- Single-level storage (disk and memory abstracted as one space)
- Hardware enforced object-based security
Performance reality :
- Clock speeds were low
- Real-world business workloads (DB2, RPG, COBOL) ran shockingly fast
- Migration between hardware generations was painless because programs weren’t tied to the CPU
From 1995 to 2000 : Transition to RISC
Processors :
- POWER / PowerPC-based CPUs
- Internally still abstracted from applications
Why this was huge :
- IBM recompiled system code automatically
- Customers upgraded hardware without recompiling apps
- Performance jumped dramatically with no application changes
Performance gain :
- Often 5–10× improvement generation-to-generation
- Especially strong in database-heavy workloads
From 2000 to 2006 : iSeries era
Processors :
- From POWER4 to POWER5+
Major advances :
- True 64-bit
- SMP scaling
- Logical Partitioning (LPARs)
Performance model introduced :
- CPW (Commercial Processing Workload) benchmark
- This became the way AS/400 performance was measured.
From 2006 to 2014 : From “System i” to “Power Systems”
Processors:
- POWER6
- POWER7
Performance highlights :
- Massive single-core performance
- Hardware-accelerated I/O
- Extremely efficient DB2 execution
- A midrange POWER7 box could replace dozens of x86 servers for ERP workloads.
From 2014 to Present : IBM i on modern POWER
Processors :
- POWER8
- POWER9
- Power10
- Power11 (current)
What’s special now :
- High core density
- Huge memory bandwidth
- SMT (Simultaneous Multithreading)
- Built-in crypto, compression, AI accelerators (POWER10)
Performance reality today :
- IBM i workloads scale linearly far better than most platforms
- Single-thread performance is still a major strength
- Reliability > raw speed (years of uptime are common)