IBM Power microprocessors

IBM has a series of high performance microprocessors called POWER followed by a number designating generation, ie POWER1, POWER2, POWER3 and so forth up to the latest POWER7+. These processor have been used by IBM in their RS/6000, AS/400, pSeries, iSeries, System p, System i and Power Systems line of servers and supercomputers. They have also been used in data storage devices by IBM and by other server manufactures like Bull and Hitachi.

The POWERn family of processors were introduced in the early 1990s and are still in active development more than 20 years later. In the beginning, the utilized the POWER instruction set architecture, but that evolved into PowerPC in later generations and then to Power Architecture. Today, only the naming scheme remains the same; modern POWER processors does not use the POWER instruction set.

History

Early development

The 801 research project

In 1974 IBM started a project to build a telephone switching computer with for the time immense computational power. Since the application was comparably simple, this machine would need only to perform I/O, branches, add register-register, move data between registers and memory, and would have no need for special instructions to perform heavy arithmetic. This simple design philosophy, whereby each step of a complex operation is specified explicitly by one machine instruction, and all instructions are required to complete in the same constant time, would later come to be known as RISC. When the telephone switch project was cancelled IBM kept the design for the general purpose processor and named it 801 after building #801 at Thomas J. Watson Research Center building #801.

The Cheetah project

By 1982 IBM continued to explore the superscalar limits of the 801 design by using multiple execution units to improve performance to determine if a RISC machine could maintain multiple instructions per cycle. Many changes were made to the 801 design to allow for multiple execution units and the Cheetah processor had separate branch prediction, fixed-point, and floating-point execution units. By 1984 CMOS was chosen since it allowed an increase in the level of circuit integration while improving transistor-logic performance.

The America project

In 1985, research on a second-generation RISC architecture started at the IBM Thomas J. Watson Research Center, producing the "AMERICA architecture"; in 1986, IBM Austin started developing the RS/6000 series computers based on that architecture. This was to become the first POWER processors.

POWER

In February 1990, the first computers from IBM to incorporate the POWER architecture were called the "RISC System/6000" or RS/6000. These RS/6000 computers were divided into two classes, workstations and servers, and hence introduced as the POWERstation and POWERserver. The RS/6000 CPU had 2 configurations, called the "RIOS-1" and "RIOS.9" (or more commonly the POWER1 CPU). A RIOS-1 configuration had a total of 10 discrete chips - an instruction cache chip, fixed-point chip, floating-point chip, 4 data L1 cache chips, storage control chip, input/output chips, and a clock chip. The lower cost RIOS.9 configuration had 8 discrete chips - an instruction cache chip, fixed-point chip, floating-point chip, 2 data cache chips, storage control chip, input/output chip, and a clock chip.

The POWER1 is the first microprocessor that used register renaming and out-of-order execution. A simplified and less powerful version of the 10 chip RIOS-1 was made in 1992 was developed for lower-end RS/6000's. It used only one chip and was called "RISC Single Chip" or RSC.

POWER1 processors

RIOS-1 - The original 10 chip version.
RIOS.9 - A less powerful version of RIOS-1.
POWER1+ - A faster version of RIOS-1 made on a reduced fabrication process.
POWER1++ - An even faster version of RIOS-1.
RSC - A single-chip implementation of RIOS-1.
RAD6000 - A radiation hardened version of the RSC was made available for primarily use in space. It was a very popular design and was used extensively on many high profile missions.

POWER2

IBM started the POWER2 processor effort as a successor to the POWER1. By adding a second fixed-point unit, a second powerful floating point unit, and other performance enhancements and new instructions to the design the POWER2 architecture had leadership performance when it was announced in November 1993. The POWER2 was a multi chip design but IBM also made a singe chip design of it, called the POWER2 Super Chip or P2SC that went into high performance servers and supercomputers. At the time of its introduction in 1996, the P2SC was the largest and the procesosr with the highest transistor count in the industry and was a leader in floating point operations.

POWER2 processors

POWER2 - The 6-8 chips was mounted on a ceramic multi chip module.
POWER2+ - A cheaper 6 chip version of POWER2 with support for external L2 caches.
P2SC - A faster and single chip version of POWER2.
P2SC+ - An even faster version or P2SC due to reduced fabrication process.

PowerPC

In 1991 Apple looked for a future alternative to Motorola's 68000 based CISC platform, and Motorola experimented with a RISC platform of its own, the 88000. IBM joined the discussion and the three founded AIM alliance to build the PowerPC architecture, heavily based on POWER architecture but with additions from both Apple and Motorola. It was ready in 1993 and was a complete 32/64 bit RISC architecture with a promise to range from very low end embedded microcontrollers to the very high end supercomputer and server applications.

After two years of development, the resulting PowerPC architecture was introduced in 1993. A modified version of the RSC architecture, PowerPC added single-precision floating point instructions and general register-to-register multiply and divide instructions, and removed some POWER feature. It also added a 64-bit version of the architecture and support for SMP.

The Amazon project

In 1990 IBM wanted to merge the low end server and mid range server architectures, the RS/6000 RISC architecture and AS/400 CISC architecture into one common RISC architecture that could host both IBM's AIX and OS/400 operating systems. The existing POWER and the upcoming PowerPC architectures were deemed unsuitable by the AS/400 team so an extension to the 64-bit PowerPC instruction set was developed called PowerPC AS for Advances Series or Amazon Series. Later, additions from the RS/6000 team and AIM Alliance PowerPC was included and by 2001 they were all joined into one architecture.

POWER3

The POWER3 began its life as "PowerPC 630" as a successor of the commercially unsuccessful PowerPC 620. It used a combination of the POWER2 instruction set and the 32/64-bit PowerPC instruction set with support for SMP and single chip implementation. It was used to great extent in IBM's RS/6000 computers and the second generation version, the POWER3-II was the first commercially available processor from IBM using copper interconnects. The POWER3 was the last processor using a POWER instruction set, from now on all used some version of the PowerPC instruction set.

POWER3 processors

POWER3 - Introduced in 1998, it combined the POWER and PowerPC instruction sets.
POWER3-II - An faster POWER3 fabricated on a reduced size, copper based process.

POWER4

The POWER4 merged the 32/64 bit PowerPC instruction set and the 64-bit PowerPC AS instruction set from the Amazon project to the new PowerPC v.2.0 specification, unifying IBM's RS/6000 and AS/400 families of computers. Besides the unification of the different platforms, POWER4 was also designed to reach very high frequencies and have large on die L2 caches. It was the first commercially available multi-core processor and came in singe die versions as well as in four chip multi chip modules. In 2002, BM also made a cost and feature reduced version of the POWER4 called PowerPC 970 by Apple's request.

POWER4 processors

POWER4 - The first dual core microprocessor and the first PowerPC processor to reach beyond 1 GHz.
POWER4+ - A faster POWER4 fabricated on a reduced process.

POWER5

The POWER5 processors built on the popular POWER4 and incorporated simultaneous multithreading into the design, a technology pioneered in the PowerPC AS based RS64-III processor, and on die memory controllers. It was designed for multi processing on a massive scale and came in multi chip modules with onboard large L3 cache chips.

POWER5 processors

POWER5 - The iconic setup with four POWER5 chips and four L3 cache chips on a large multi chip module.
POWER5+ - A faster POWER5 fabricated on a reduced process maily to reduce power consumption.

Power Architecture

A joint organization was founded in 2004 called Power.org with the mission to unify and coordinate future development of the PowerPC specifications. By then the PowerPC specification was fragmented since Freescale (née Motorola) and IBM had taken different paths in their respective development of it. Freescale had prioritized 32-bit embedded applications and IBM high end servers and supercomputers. There was also a collection of licensees of the specification like AMCC, Synopsys, Sony, Microsoft, P.A. Semi, CRAY and Xilinx that needed coordination. The joint effort was not only to streamline development of the technology but also to streamline marketing.

The new instruction set architecture was called Power Architecture and merged the PowerPC v.2.02 from the POWER5 with the PowerPC Book E specification from Freescale as well as some related technologies like AltiVec (called VMX by IBM) and hardware virtualization. This new ISA was called Power ISA v.2.03 and POWER5 was the first high end processor from IBM to use it. Older POWER and PowerPC specifications didn't make the cut and those instruction sets were henceforth deprecated for good. There's no active development on any processor type today that uses these older instruction sets.

POWER6

POWER6 was the fruit of the ambitions eCLipz Project, joining the I (AS/400), P (RS/6000) and Z (Mainframe) architectures under one common platform. I and P was already joined with the POWER4, but the eCLipz effort failed to include the CISC based z/Architecture and where the z10 processor became POWER6's eCLipz sibling. </Architecture remains a separate design track to this day not related to Power Architecture instruction set in any way.

Because of eCLipz the POWER6 is an unusual design as it aimed for very high frequencies and sacrificed out-of-order execution, something that's been a feature for POWER and PowerPC processors since their inception. POWER6 also introduced the decimal floating point unit to the Power ISA, something it shares with z/Architecture.

With the POWER6, in 2008 IBM merged the former System p and System i server and workstation families into one family calling it Power Systems. Power Systems machines can run different operating systems like AIX, Linux and IBM i.

POWER6 processors

POWER6 - Reached 5 GHz comes in modules with a singe chip on it , and in MCM with two L3 cache chips.
POWER6+ - A minor update, and fabricated on the same process as POWER6.

POWER7

The POWER7 symmetric multiprocessor architecture was a substantial evolution from the POWER6 design, focusing more on power efficiency through multiple cores, simultaneous multithreading (SMT), out of order execution and large on die L3 caches. The eight core chip could execute 32 threads in parallel, and has a mode in which it could disable cores to reach higher frequencies for the ones that's left. It uses a new high performance floating point unit called VSX that merges the functionality of the traditional FPU with AltiVec. Even while the POWER7 run at lower frequencies than POWER6 each POWER7 core performed faster than its POWER6 counterpart.

POWER7 processors

POWER7 - Comes in single chip modules or in quad chip MCM-configurations for supercomputer applications.
POWER7+ - Reduced fabrication process, and increased L3 cache and frequency.

Devices

Name	ISA	bits	cores	Fab	Transistors	die size	L1	L2	L3	Clock	Package	Introduced
RIOS-1	POWER	32 bits	1	1.0 μm	6.9 M	1.284 mm²	8 kB I 64 kB D	n/a	n/a	20-30 MHz	10 chips in CPGA on PCB	1990
RIOS.9	POWER	32 bits	1	1.0 μm	6.9 M		8 kB I 32 kB D	n/a	n/a	20-30 MHz	8 chips in CPGA on PCB	1990
POWER1+	POWER	32 bits	1		6.9 M		8 kB I 64 kB D	n/a	n/a	25-41.6 MHz	8 chips in CPGA on PCB	1991
POWER1++	POWER	32 bits	1		6.9 M		8 kB I 64 kB D	n/a	n/a	25-62.5 MHz	8 chips in CPGA on PCB	1992
RSC	POWER	32 bits	1	0.8 μm	1 M	226.5 mm²	8 kB unified	n/a	n/a	33-45 MHz	201 pin CPGA	1992
POWER2	POWER2	32 bits	1	0.72 μm	23 M	1042.5 mm² 819 mm²	32 kB I 128-265 kB D	n/a	n/a	55-71.5 MHz	6-8 dies on ceramic 734 pin MCM	1993
POWER2+	POWER2	32 bits	1	0.72 μm	23 M	819 mm²	32 kB I 64-128 kB D	0.5 - 2 MB external	n/a	55-71.5 MHz	6 chips in CBGA on PCB	1994
P2SC	POWER2	32 bits	1	0.29 μm	15 M	335 mm²	32 kB I 128 kB D	n/a	n/a	120-135 MHz	CCGA	1996
P2SC+	POWER2	32 bits	1	0.25 μm	15 M		32 kB I 128 kB D	n/a	n/a	160 MHz	CCGA	1997
RAD6000	POWER	32 bits	1	0.5 μm	1.1 M		8 kB unified	n/a	n/a	20-33 MHz	Rad hard	1997
POWER3	POWER2 PowerPC 1.1	64 bits	1	0.35 μm	15 M	270 mm²	32 kB I 64 kB D	1-16 MB external	n/a	200-222 MHz	1088 pin CLGA	1998
POWER3-II	POWER2 PowerPC 1.1	64 bits	1	0.25 μm Cu	23 M	170 mm²	32 kB I 64 kB D	1-16 MB external	n/a	333-450 MHz	1088 pin CLGA	1999
POWER4	PowerPC 2.00 PowerPC-AS	64 bits	2	180 nm	174 M	412 mm²	64 kB I 32 kB D per core	1.41 MB per core	32 MB external	1-1.3 GHz	1024 pin CLGA ceramic MCM	2001
POWER4+	PowerPC 2.01 PowerPC-AS	64 bits	2	130 nm	184 M	267 mm²	64 kB I 32 kB D per core	1.41 MB per chip	32 MB external	1.2-1.9 GHz	1024 pin CLGA ceramic MCM	2002
POWER5	PowerPC 2.02 Power ISA 2.03	64 bits	2	130 nm	276 M	389 mm²	32 kB I 32 kB D per core	1.875 MB per chip	32 MB external	1.5-1.9 GHz	ceramic DCM ceramic QCM	2004
POWER5+	PowerPC 2.02 Power ISA 2.03	64 bits	2	90 nm	276 M	243 mm²	32 kB I 32 kB D per core	1.875 MB per chip	32 MB external	1.5-2.3 GHz	ceramic DCM ceramic QCM ceramic MCM	2005
POWER6	Power ISA 2.03	64 bits	2	65 nm	790 M	341 mm²	64 kB I 64 kB D per core	4 MB per core	32 MB external	3.6-5 GHz	CLGA OLGA	2007
POWER6+	Power ISA 2.03	64 bits	2	65 nm	790 M	341 mm²	64 kB I 64 kB D per core	4 MB per core	32 MB external	3.6-5 GHz	CLGA OLGA	2009
POWER7	Power ISA 2.06	45 bits	4-8	45 nm	1.2 B	567 mm²	32 kB I 32 kB D per core	256 kB per core	32 MB per chip	2.4-4.25 GHz	CLGA OLGA organic QCM	2010
POWER7+	Power ISA 2.06	64 bits	4-8	32 nm	2.2 B	567 mm²	32 kB I 32 kB D per core	256 kB per core	80 MB per chip	2.4-4.4 GHz	CLGA OLGA organic QCM	2012