PowerPC 970

Artist's rendering of a PowerPC 970 CPU
General information
Launched	2002
Designed by	IBM
Common manufacturer	IBM
Performance
Max.CPUclock rate	1.0 GHz  to 2.7 GHz
Physical specifications
Cores	1-2
Cache
L1cache	64 KB instruction 32 KB data
L2 cache	512–1024 KB
Architecture and classification
Application	Desktop
Technology node	130 nm to90 nm
Microarchitecture	ppc970,POWER4
Instruction set	32/64-bitPowerPC 2.01
Products, models, variants
Variant	970, 970FX, 970MP
History
Predecessor	POWER4

ThePowerPC 970,PowerPC 970FX, andPowerPC 970MP are64-bitPowerPCCPUs fromIBM introduced in 2002.Apple branded the 970 asPowerPC G5 for itsPower Mac G5.

Having created the PowerPC architecture in the early 1990s via theAIM alliance, the 970 family was created through a further collaboration between IBM andApple.^[1][2] The project wascodenamed GP-UL or Giga Processor Ultra Light, where Giga Processor is the codename for thePOWER4 from which the core was derived. When Apple introduced thePower Mac G5, it stated that this was a five-year collaborative effort, with multi-generation roadmap. This forecast however was short-lived when Apple later had to retract its promise to deliver a 3 GHz processor only one year after its introduction. IBM was also unable to reduce power consumption to levels necessary for laptop computers. Ultimately, Apple only used three variants of the processor.

IBM's JS20/JS21blade modules and some low-endworkstations andSystem p servers are based on the PowerPC 970. It is also used in some high end embedded systems likeMercury's Momentum XSA-200. IBM is also licensing the PowerPC 970 core for use in custom applications.

The PowerPC 970 is a single core derivative of thePOWER4 and can process both32-bit and64-bit PowerPCinstructions natively. It has a hardwareprefetch unit and a three waybranch prediction unit.

Like the POWER4, the front-end is nine stages long. The PowerPC 970 can fetch and decode up to eight instructions, dispatch up to five to reserve stations, issue up to eight to the execution units and retire up to five per cycle. The execution pipelines were lengthened compared to the POWER4 to achieve higherIPC. It has eight execution units: twoarithmetic logic units (ALUs), twodouble-precisionfloating-point units, two load/store units and twoAltiVec units.^[3]

One of the AltiVec units executes integer and floating-point instructions, and the other only permute instructions. The latter has three subunits for simple integer, complex integer and floating-point instructions. These units have pipelines of varying lengths: 10 stages for simple integer and permute instructions, 13 stages for complex integer instructions and 16 stage for floating-point instructions.^[3]

The processor has two unidirectional 32-bitdouble data rate (DDR) buses (one for reads, the other for writes) to the system controller chip (northbridge) running at one quarter of the processor core speed. The buses also carry addresses and control signals in addition to data so only a percentage of the peak bandwidth can be realized (6.4 GB/s at 450 MHz). As the buses are unidirectional, each direction can realize only half the aggregate bandwidth, or 3.2 GB/s.^[3]

All generations of 970 processors were manufactured in IBM's East Fishkill plant in New York on a white ceramic substrate that was typical for IBM's high end processors of the era.

The first PowerPC 970 was manufactured on a 130 nm process in week 20 of 2003.^[4]

The PowerPC 970FX was manufactured on a 90 nm process in week 25 of 2004,^[4] with the smaller die.

The PowerPC 970MP has two cores on the same die and twice the L2 cache per core than the 970FX so its size is much larger. It was manufactured in week 24 of 2005.^[4]

ThePowerPC 970 was announced by IBM in October 2002. It was released inApple Computer'sPower Mac G5 in June 2003. Like its naming convention of G3 and G4, Apple branded the PowerPC 970 based products as G5, for the fifth generation of PowerPC. IBM released its first PowerPC 970 blade servers, theBladeCenter JS20, in November 2003.

The PowerPC 970 has 512 KB of full-speedL2 cache and clock speeds from 1.6 to 2.0 GHz. The front side bus runs at half the processor's clock speed.

ThePowerPC 970FX has a90 nm manufacturing process and has a maximum power rating of 11 watts at 149 degrees Fahrenheit (65 °C) while clocked at 1 GHz and a maximum of 48 watts at 2 GHz.^[5]

It has 10 functional units – 2 Fixed-Point Units, 2 Load/Store Units, 2 Floating Point Units, 1 Branch Unit, 1 SIMD ALU unit, 1 SIMD Permute unit, and 1 Condition Register. It supports up to 215 instructions in-flight: 16 in the Instruction Fetch Unit, 67 in the Instruction Decode Unit, 100 in the Functional Units, and 32 in the Store Queue. It has 64 KBs of directly mapped Instruction Cache and 32 KBs of D-Cache.^[6]

Apple released 970FX-powered machines throughout 2004: theXserve G5 in January, the Power Mac G5 in June, and theiMac G5 in August. The Power Mac introduced a top clock speed of 2.5 GHz whileliquid-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.

Market demand was intense for a faster laptop CPU than the G4, but Apple never delivered a G5 series CPU inPowerBook laptops. The original 970 uses far too much power and was never seriously viewed as a candidate for a portable computer. The 970FX reducedthermal design power (TDP) to about 30W at 1.5 GHz, which led many users to believe a PowerBook G5 might be possible. However, several obstacles prevented even the 970FX from being used in this application. At 1.5 GHz, the G5 was not substantially faster than the 1.5 and 1.67 GHz G4 processors, which Apple used in PowerBooks instead. Furthermore, the northbridge chips available to interface the 970FX to memory and other devices were not designed for portable computers, and consumed too much power. Finally, the 970FX had inadequate power saving features for a portable CPU. Its minimum (idle) power was much too high, which would have led to poor battery life figures in a notebook computer.^{[citation needed]}

IBM announced thePowerPC 970MP,codenamed "Antares", on July 7, 2005, at the Power Everywhere forum in Tokyo. The 970MP is a dual-core derivative of the 970FX with clock speeds between 1.2 and 2.5 GHz, and a maximum power usage of 75 W at 1.8 GHz and 100 W at 2.0 GHz. Each core has 1 MB ofL2 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.^[7] The 970MP also includes partitioning and virtualization features.^[8][9]

The PowerPC 970MP replaced the PowerPC 970FX in Apple's high-endPower Mac G5 computers, while theiMac G5 and the legacyPCI-X Power Mac G5 continued to use the PowerPC 970FX processor. The PowerPC 970MP is used in IBM's JS21 blade modules, IBM Intellistation POWER 185 workstation and YDL PowerStation byFixstars Solutions (Yellow Dog Linux (YDL) PowerStation).

Due to high power requirements, IBM discontinued units above 2.0 GHz.

Two dedicatednorthbridges for PowerPC 970-based computers were manufactured by IBM:

• CPC925 – Designed by Apple^[10] and called theU3 or theU3H (which supportsECC memory). It is capable of supporting up to two PowerPC 970s or PowerPC 970FXs and has two 550 MHz unidirectional processor buses, a 400 MHzDDR memory controller, x8AGP and a 400 MHz 16-bitHyperTransport tunnel. It fabricated on a 130 nm process. Additionally, there was an unreleased U3Lite northbridge in development for the PowerBook G5, which never made it to market.
• CPC945 – Designed by IBM and calledU4 by Apple, it is capable of supporting two PowerPC 970MPs and has two 625 MHz unidirectional processor buses, two memory controllers that support up to 64 GB of 533 MHz DDR2 SDRAM with ECC capability and has a x16PCIe lane and an 800 MHz 16-bit HyperTransport tunnel. It is fabricated on a 90 nm process.

A CPC965 northbridge was canceled. Slated for release in 2007, it was to be a uniprocessor-only northbridge. Its features were a 533 MHz DDR2 controller that supported up to 8 GB ECC memory, a 8x PCIe bus, integrated four-portGigabit Ethernet withIPv4TCP/UDP offloading, USB 2.0 ports, aFlash-interface. The northbridge contains an integratedPowerPC 405 core to provide system management and configuration capabilities.^[11]

IBM uses its proprietaryElastic Interface (EI) bus in the modules.

• Supercomputers using the PowerPC 970:
  • System X
  • Some previous models of supercomputers in theSpanish Supercomputing Network used PowerPC processors, such asMagerit version 1 andMareNostrum version 2.
• List of Macintosh models grouped by CPU type

• "IBM's PPC970 Becomes Apple's G5". (July 7, 2003).Microprocessor Report.
• "IBM Takes the Lead". (February 9, 2004).Microprocessor Report.
• "IBM's Double-Shot of PowerPC". (November 7, 2005).Microprocessor Report.

• Ars Technica article, part I
• Ars Technica article, part II
• IBM PowerPC 970FX RISC Microprocessor User's Manual
• Understanding 64-bit PowerPC architecture
• ISSCC 2006: IBM PowerPC 970MP
• IBM Documentation:PowerPC 9XX Microprocessors

• PowerPC microprocessors
• IBM microprocessors
• Power microprocessors
• 64-bit microprocessors

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