PowerPC G5

The PowerPC 970, PowerPC 970FX, PowerPC 970GX, and PowerPC 970MP, are 64-bit Power Architecture processors from IBM introduced in 2002. The processor family was named the PowerPC G5 by Apple for use in the Power Mac G5 and iMac G5.

The 970 family was created through a collaboration between IBM and Apple[1][2]. The project went under the codename GP-UL or Giga Processor Ultra Light, where Giga Processor was the codename for the POWER4 from which the core was derived. When Apple introduced the Power Mac G5 they stated that this was a five year collaborative effort, with multiple future generations, but it was short-lived. Apple had to retract the promise to deliver a 3 GHz processor one year after its introduction and IBM could never get the power consumption down far enough for these processors to fit into a portable computer. Apple only used three variants of the processor.

IBM’s JS20/JS21 blade modules and some low-end workstations and System p servers are based on PowerPC 970. It is also used in some high end embedded systems like Mercury’s Momentum XSA-200. IBM is also licensing the PowerPC 970 core for use in custom applications. A common misconception is that the PowerPC 970 was the core in IBM's Xenon processor in Microsoft's Xbox 360, but this is false. That processor is using cores similar to the Power Processing Element (PPE) in the Cell microprocessor.

Design

PowerPC 970FX Processor

The PowerPC 970 is a single core, streamlined version of the POWER4 and can process both 32-bit and 64-bit PowerPC instructions natively. It has a hardware prefetch unit and a three way branch prediction unit which can track over 200 instructions simultaneously, issuing up to five instructions per cycle to any of eight processing units (two integer, two double precision floating point, two load/store units and two AltiVec SIMD units). The processor has a bi-directional 32-bit front side bus to the system controller chip (northbridge) running at up to half the processor core speed.

Processors

PowerPC 970

The PowerPC 970 was announced by IBM in October 2002. It was released in Apple Computer's Power Mac G5 in June 2003 (in keeping with its previous naming conventions, Apple termed the PowerPC 970 based products G5, for the fifth generation of PowerPC microprocessors). IBM released its first PowerPC 970 blade servers, the BladeCenter JS20, in November 2003.

The PowerPC 970 had 512 KiB of full-speed L2 cache and clock speeds from 1.6 to 2.0 GHz. The front side bus ran at half the processor's clock speed.

PowerPC 970FX

The PowerPC 970FX used a 90 nm manufacturing process and has a maximum power rating of 11 watts at 149 degrees Fahrenheit (65 °C) while clocked at 1GHz and a maximum of 48 watts at 2GHz.^{[citation needed]}

Apple released their 970FX-powered machines throughout 2004: the Xserve G5 in January, the Power Mac G5 in June, and the iMac G5 in August. The Power Mac introduced a top clock speed of 2.5 GHz while liquid-cooled (eventually reaching as high as 2.7 GHz in April 2005). The iMac ran the front side bus at a third of the clock speed.

PowerPC 970MP

IBM released the PowerPC 970MP, code-named "Antares", in the 3rd quarter of 2005. The 970MP is a dual-core processor with clock speeds between 1.2 and 2.5 GHz, and a maximum power usage of 75 watts at 1.8GHz and 100 watts at 2.0GHz. Each core has 1 MiB of L2 cache, twice that of the 970FX. Like the 970FX, this chip was produced at the 90 nm process. When one of the cores is idle, it will enter a "doze" state and shut down. [3] The 970MP also includes partitioning and virtualization features. [4][5]

The PowerPC 970MP replaced the PowerPC 970FX in Apple's high-end Power Mac G5 computers, while the iMac G5 and the legacy PCI-X Power Mac G5 continued to use the PowerPC 970FX processor. The PowerPC 970MP is used in IBM's JS21 blade modules.

Due to high power requirements IBM has chosen to discontinue parts running faster than 2.0 GHz.

Northbridges

There are two dedicated northbridges for PowerPC 970-based computers, both manufactured by IBM:

• CPC925 — Designed by Apple and called the U3 or the U3H (which supports ECC memory). It is capable of supporting up to two PowerPC 970s or PowerPC 970FXs and has two 550 MHz bi-directional processor buses, a 400 MHz DDR memory controller, x8 AGP and a 400 MHz 16-bit HyperTransport tunnel. It fabricated on a 130 nm process.

• CPC945 — Designed by IBM and called U4 by Apple, it is capable of supporting two PowerPC 970MPs and has two 625 MHz bi-directional processor buses, two memory controllers that support up to 64 GB of 533 MHz DDR2 SDRAM with ECC capability and has a x16 PCIe lane and an 800 MHz 16-bit HyperTransport tunnel. It is fabricated on a 90 nm process.

Buses

IBM uses its proprietary Elastic interface bus in the modules.^[1]

References

1. ^ Guillaume Peron, "IBM PowerPC 970FX power-on reset mechanism" 15 Dec 2005

See also

• POWER3, POWER4 and POWER5
• PowerPC G4 and Altivec
• Power Mac G5 and Xserve G5
• System X and MareNostrum — supercomputers using the PowerPC 970.

External links

• ArsTechnica article, part I
• ArsTechnica article, part II
• IBM PowerPC 970FX RISC Microprocessor User's Manual
• Understanding 64-bit PowerPC architecture
• PowerPC G5 operating systems from LynuxWorks for embedded systems
• ISSCC 2006: IBM PowerPC 970MP
• VME PowerPC 970 Rugged Blade Computer from Thales Computers