Power Mac G5

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Power Mac G5

The Power Mac G5 is Apple Computer's name for models of the Power Mac which utilize the PowerPC G5 CPU. The professional-grade computer is the most powerful of all the computers Apple makes.



The current revision of the Power Mac G5 is available in three PowerPC G5 dual-processor configurations, clocked at 2.0, 2.3, and 2.7GHz, as well as a single-processor, 1.8GHz model. Prices range from $1499 (USD) for the single-processor 1.8GHz configuration to $2999 (USD) for a dual-processor 2.7GHz configuration. The dual-processor G5 configuration can communicate through its front side bus (FSB) at half its internal clock speed, while the 1.8GHz single-processor model communicates through a front side bus one-third the clock speed of its processor (600MHz). Each processor in the Power Mac G5 has two unidirectional 32-bit pathways: one leading to the processor and the other from the processor. These result in a total bandwidth of up to 20 GB/s. The processor at the heart of the Power Mac G5 has a "superscalar, superpipelined" execution core that can handle up to 216 in-flight instructions, and uses a 128-bit, 162-instruction SIMD unit.

In addition, due to the 64-bit processor (and therefore 42-bit MMU) the Power Mac G5 has a RAM capacity greater than the four gigabyte addressable memory limit of 32 bit processors. Currently the Power Mac G5 can hold eight gigabytes using eight RAM slots with 1 GB per stick. This is a full four gigabytes above current theoretical limits on 32-bit processors, though it should be noted that, despite Apple's eight-gigabyte claim, it can most likely hold sixteen gigabytes due to the U3 memory controller limits, using 2GB RAM sticks. The Power Mac G5's PowerPC 970 processor itself is capable of addressing 242 bytes (4 terabytes) of physical RAM and 264 bytes (8 exabytes) of Virtual RAM. Obviously there are no RAM modules of that density, but the potential alone inspires appreciation in some. The memory in the Power Mac G5 is the equivalent of Dual-Channel DDR400, but Apple likes to call it "128-bit DDR" instead of Dual-Channel. This means there is a theoretical bandwidth of 6.4 GB/s.

The large case has room, after installing the mounting plate, for six 500GB internally-powered SATA hard drives for a total inner capacity of 3 TB (3072 GB). Two 500GB external SATA drives bring the G5's total capacity to around 4 TB. (see G5Jam)

1100 Power Mac G5s formed the processing nodes of Virginia Tech's original Mac OS X computer cluster supercomputer (a.k.a. supercluster) known as The Big Mac. The computer was soon dismantled and replaced with a new cluster made of an equal number of Apple's Xserve rack-mounted servers, which also use the G5 chip running at 2.3 GHz.

In 2003 Steve Jobs promised that the Power Mac G5 would reach 3GHz one year after it was announced. However, today the G5 has only reached 2.7GHz and for this many Macintosh users are disgruntled.

PowerPC G5 processor

The PowerPC G5 (called the PowerPC 970FX by its manufacturer, IBM) is based upon IBM's dual-core POWER4 microprocessor. At the introduction of the Power Mac G5, Apple announced a partnership with IBM in which IBM would continue to produce PowerPC variants of their Power processors. According to IBM's Dr. John E. Kelly, "The goal of this partnership is for Apple and IBM to come together so that Apple customers get the best of both worlds, the tremendous creativity from the Apple corporation and the tremendous technology from the IBM corporation. IBM invested over 3 billion dollars in a new lab to produce these large, 300-millimetre wafers." (This lab is a completely automated facility located in East Fishkill, New York, and figures heavily in IBM's microelectronics strategy above and beyond the partnership with Apple.) The PowerPC G5 microprocessor has 58 million transistors and is manufactured using IBM CMOS 9S at 90nm fabrication process. That's 1/1000th the diameter of a human hair. CMOS 9S is the combination of SOI, Low-k dielectric insulation, and Copper interconnect technology, which were invented at IBM research in the mid-90's.

Also, IBM has already built the POWER5, which is rumored to be the basis for the next generation of PowerPC processors. The POWER5 has numerous improvements over the POWER4, including simultaneous multithreading, further power management features, dedicated single-tasking mode, Hypervisor (virtualization technology), and eFuse (self-tuning logic). Due to the SMT capability and quad-core nature of the POWER5, it would appear to the operating system as 8 CPUs -- 4 physical cores with two logical CPUs per core.

Product revision history

(Note: DP designates a Dual-Processor machine, and SP designates a Single-Processor machine)

  • 2003 June: Initial release at speeds of SP 1.6, SP 1.8, DP 2.0GHz
  • 2003 November: DP 1.8 replaces SP 1.8GHz; a price reduction on SP 1.6GHz
  • 2004 June: 90nm DP 1.8, DP 2.0 and liquid-cooled DP 2.5GHz replace all previous models
  • 2004 October: A new SP 1.8 reintroduced, with a slower, 600MHz FSB (Frontside Bus), likely based upon the iMac G5's architecture
  • 2005 April: A new DP 2.3 (1.15ghz FSB) and DP 2.7 (1.35ghz FSB) were released while keeping the SP 1.8 and the DP 2.0. Newly introduced features were the 16x Double-Layer SuperDrives across the line and increased storage, up to 800GB for the higher-end models. The SP 1.8 model was discontinued in June 2005.

A partial list of official firmware updates


External links


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