POWER4

HistoryPredecessor(s)POWER3, RS64Successor(s)POWER5

POWER, PowerPC, and Power ISA architectures
NXP (formerly Freescale and Motorola)
PowerPC e series (2006) e200 e300 e500 e600 e5500 e6500 Qor series (2008) QorIQ Qorivva
IBM
Power series (1990) POWER1 POWER2 POWER3 POWER4 POWER5 POWER6 POWER7 POWER8 POWER9 Power10 PowerPC series (1992) 6xx 4xx 7xx 74xx 970 A2 (2010) A2I A2O RAD series (1997) RAD6000 RAD750 RAD5500 RS64 series (1996)
IBM/Nintendo
Gekko Broadway Espresso
Other
Titan PWRficient Cell Xenon X704
Related links
OpenPOWER Foundation AIM alliance RISC Blue Gene Power.org PAPR PReP CHRP AltiVec
Cancelled in gray, historic in italic
v t e

The POWER4 is a microprocessor developed by International Business Machines (IBM) that implemented the 64-bit PowerPC and PowerPC AS instruction set architectures. Released in 2001, the POWER4 succeeded the POWER3 and RS64 microprocessors, enabling RS/6000 and eServer iSeries models of AS/400 computer servers to run on the same processor, as a step toward converging the two lines. The POWER4 was a multicore microprocessor, with two cores on a single die, the first non-embedded microprocessor to do so.^[1] POWER4 Chip was first commercially available multiprocessor chip.^[2] The original POWER4 had a clock speed of 1.1 and 1.3 GHz, while an enhanced version, the POWER4+, reached a clock speed of 1.9 GHz. The PowerPC 970 is a derivative of the POWER4.

Functional layout

The POWER4 has a unified L2 cache, divided into three equal parts. Each has its own independent L2 controller which can feed 32 bytes of data per cycle.^{[clarification needed]} The Core Interface Unit (CIU) connects each L2 controller to either the data cache or instruction cache in either of the two processors. The Non-Cacheable (NC) Unit is responsible for handling instruction serializing functions and performing any noncacheable operations in the storage topology. There is an L3 cache controller, but the actual memory is off-chip. The GX bus controller controls I/O device communications, and there are two 4-byte wide GX buses, one incoming and the other outgoing. The Fabric Controller is the master controller for the network of buses, controlling communications for both L1/L2 controllers, communications between POWER4 chips {4-way, 8-way, 16-way, 32-way} and POWER4 MCM's. Trace-and-Debug, used for First Failure Data Capture, is provided. There is also a Built In Self Test function (BIST) and Performance Monitoring Unit (PMU). Power-on reset (POR) is supported.

Execution units

The POWER4 implements a superscalar microarchitecture through high-frequency speculative out-of-order execution using eight independent execution units. They are: two floating-point units (FP1-2), two load-store units (LD1-2), two fixed-point units (FX1-2), a branch unit (BR), and a conditional-register unit (CR). These execution units can complete up to eight operations per clock (not including the BR and CR units):

• each floating point unit can complete one fused multiply–add per clock (two operations),
• each load–store unit can complete one instruction per clock,
• each fixed-point unit can complete one instruction per clock.

The pipeline stages are:

• Branch Prediction
• Instruction Fetch
• Decode, Crack and Group Formation
• Group Dispatch and Instruction Issue
• Load–Store Unit Operation
  • Load Hit Store
  • Store Hit Load
  • Load Hit Load
• Instruction Execution Pipeline

Multi-chip configuration

The POWER4 also came in a configuration using a multi-chip module (MCM) containing four POWER4 dies in a single package, with up to 128 MB of shared L3 ECC cache per MCM.

Parametrics

POWER4 180 nm@CMOS 8S3 SOI

Clock GHz	1.3 GHz
Power	115 W	1.5 V @ 1.1 GHz
Transistors		174 million
Gate L	90 nm
Gate oxide		2.3 nm
Metal-layer	pitch	thickness
M1	500 nm	310 nm
M2	630 nm	310 nm
M3-M5	630 nm	20 nm
M6(MQ)	1260 nm	920 nm
M7(LM)	1260 nm	920 nm
Dielectric	~4.2
Vdd	1.6 V

POWER4+

The POWER4+, released in 2003, was an improved version of the POWER4 that ran at up to 1.9 GHz.^[3] It contained 184 million transistors, measured 267 mm², and was fabricated in a 0.13 μm SOI CMOS process with eight layers of copper interconnect.

See also

• PowerPC 970
• IBM Power microprocessors

Notes

References

• "Power4 Focuses on Memory Bandwidth". (6 October 1999). Microprocessor Report.
• "IBM's Power4 Unveiling Continues". (20 November 2000). Microprocessor Report.
• "POWER4 System Microarchitecture" (PDF). IBM. Archived from the original (PDF) on 2013-11-07. Retrieved 2012-06-07.
• J. M. Tendler; J. S. Dodson; J. S. Fields, Jr.; H. Le & B. Sinharoy (2002). "POWER4 system microarchitecture". IBM Journal of Research and Development. 46 (1): 5–26. doi:10.1147/rd.461.0005. ISSN 0018-8646. Retrieved 2006-07-21.
• J. D. Warnock; J. M. Keaty; J. Petrovick; J. G. Clabes; C. J. Kircher; B. L. Krauter; P. J. Restle; B. A. Zoric & C. J. Anderson (2002). "The circuit and physical design of the POWER4 microprocessor". IBM Journal of Research and Development. 46 (1): 27–52. doi:10.1147/rd.461.0027. ISSN 0018-8646. Retrieved 2006-07-21.