Power Mac G5

Apple Power Mac G5
Developer	Apple Computer, Inc.
Product family	Power Macintosh
Type	Desktop
Release date	June 23, 2003
Introductory price	US$1,999 (equivalent to $3,420 in 2024)
Discontinued	August 7, 2006
CPU	1.6 – 2.7 GHzPowerPC G5 Single-processor Dual-processors, single-core Dual-core Dual-processors, dual-core
Predecessor	Power Mac G4
Successor	Mac Pro
Related	iMac G5 PowerBook G4

ThePower Mac G5 is a series ofpersonal computers designed, manufactured, and sold byApple Computer, Inc. from 2003 to 2006 as part of thePower Mac series. When introduced, it was the most powerful computer in Apple'sMacintosh lineup, and was marketed by the company as the world's first 64-bit desktop computer.^[1] It was also the first desktop computer from Apple to use ananodizedaluminum alloy enclosure, and one of only three computers in Apple's lineup to utilize thePowerPC 970 CPU, the others being theiMac G5 and theXserve G5.

Three generations of Power Mac G5 were released before it was discontinued as part of theMac transition to Intel processors, making way for its replacement, theMac Pro. The Mac Pro retained a variation of the G5's enclosure design for seven more years, making it among the longest-lived designs in Apple's history.^[2]

Officially launched as part ofSteve Jobs'keynote presentation at theWorldwide Developers Conference in June 2003, the Power Mac G5 was introduced with three models, sharing the same physical case, but differing in features and performance. Although somewhat larger than the G4tower it replaced, the necessity for a complex cooling system meant that the G5 tower had room inside for only one optical drive and two hard drives.

Steve Jobs stated during his keynote presentation that the Power Mac G5 would reach 3 GHz "within 12 months." This would never come to pass; after three years, the G5 only reached 2.7 GHz before it was replaced by the IntelXeon-basedMac Pro, which debuted with processors running at speeds of up to 3 GHz.

During the presentation, Apple also showedVirginia Tech'sMac OS Xcomputer clustersupercomputer (a.k.a. supercluster) known asSystem X, consisting of 1,100 Power Mac G5 towers operating as processing nodes. The supercomputer managed to become one of the top five supercomputers that year. The computer was soon dismantled and replaced with a new cluster made of an equal number ofXserve G5 rack-mounted servers, which also used the G5 chip running at 2.3 GHz.

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The PowerPC G5 (called the PowerPC 970 by its manufacturer,IBM) is based upon IBM's 64-bitPOWER4 microprocessor. At the Power Mac G5's introduction, 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 US$3 billion in a new lab to produce these large, 300 mm wafers." This completely automated facility inEast Fishkill, New York figured heavily in IBM's larger microelectronics strategy.

The original PowerPC 970 had 50 million transistors and was manufactured using IBM CMOS 9S at 130nm fabrication process. CMOS 9S is the combination ofSOI, low-k dielectric insulation, and copper interconnect technology, which were invented at IBM research in the mid-1990s. Subsequent revisions of the "G5" processor have included IBM's PowerPC 970FX (same basic design on a 90 nm process), and the PowerPC 970MP (essentially two 970FX cores on one die). Apple refers to the dual-core PowerPC 970MP processors as either the "G5 Dual" (for single-socket, dual-core configurations), or Power Mac G5 Quad (fordual-socket, four-core configurations).

The Power Mac G5 line in 2006 consisted of three, dual-core PowerPC G5 configurations, which can communicate through itsHyperTransport at half its internal clock speed. Each processor in the Power Mac G5 has two unidirectional32-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 a128-bit, 162-instructionSIMD unit (AltiVec).

All modern 32-bit x86 processors since thePentium Pro have thePhysical Address Extension (PAE) feature, which permits them to use a 36-bit physical memory address to address a maximum of 2³⁶ bytes (64 gigabytes) ofphysical memory, while the PowerPC 970 processor is capable of addressing 2⁴² bytes (4terabytes) of physical memory and 2⁶⁴ bytes (16exabytes) ofvirtual memory. Due to its64-bit processor (and 42-bitMMU), the final revision of the Power Mac G5 can hold 16 GB ofDual-Channel DDR2 PC4200 RAM using eight memory slots, with support forECC memory.

• 2003 June: Initial release at speeds of Single 1.6, Single 1.8, Dual 2.0 GHz.
• 2003 November: Dual 1.8 replaces Single 1.8 GHz; price reduction on Single 1.6 GHz.
• 2004 June: 90 nm Dual 1.8, Dual 2.0 and Dual 2.5 GHz replace all previous models. The 2.5 GHz model is notable as the first major PC withliquid cooling included as stock.
• 2004 October: A new Single 1.8 reintroduced, with a slower, 600 MHz HyperTransport, PCI bus, based upon theiMac G5's architecture (U3lite and Shasta chips). Apple's official name for this machine is "Power Mac G5 (Late 2004)".
• 2005 April: CPU speed increased: Dual 2.5 GHz → Dual 2.7 GHz (PCI-X, more reliableliquid cooling), Dual 2.0 GHz → Dual 2.3 GHz (PCI-X), Dual 1.8 GHz → Dual 2.0 GHz (PCI). Newly introduced features were the 16x dual-layer SuperDrives across the line and increased storage, up to 800 GB for the higher-end models. The 1.8 GHz Single was not modified.
• 2005 June–July: The Single 1.8 model was discontinued in the United States and Europe.
• 2005 October: Shift to dual-core processors: Dual 2.0 GHz → DC 2.0 GHz, Dual 2.3 GHz → DC 2.3 GHz, Dual 2.7 GHz → Dual DC 2.5 GHz (termed a Quad Power Mac G5, with four CPU execution cores), all with DDR2 memory, andPCI Express expansion in place ofPCI-X.^[3][4][5] The older PCI-X, Dual 2.7 GHz model remained available for a while, but the slower speed single-core models were discontinued immediately.
• 2006 August: The Power Mac is replaced by its Intel successor, theMac Pro.

According to Apple, all of these models are obsolete.^[a][6]

Early versions of dual processor G5 computers havenoise problems. The first one isground loop-based interference,^[13] which sometimes causes noise leaks into the analog audio outputs. This bug was fixed in Rev. B G5.

The second noise problem came from the 'chirping' sound, which can be triggered by fluctuations in power draw. For example, usingExposé causes a brief chirp.^[14] A widely circulated work-around is to disable the CPUs' "nap" feature using Apple'sCHUD Tools, but this was not recommended by Apple. This noise problem was not fixed until the dual core generation of G5s was produced, however it did not affect the "Late 2004" model (at least there have never been any reports). The power draw fluctuation was later attributed to the lack of power management features in the single-core processors.^[15] Apple eventually posted the chirping bug information on its support site.^[16]

Although the noise problems did not prevent the affected computers from working, they were problematic for audio professionals and enthusiasts, especially for the liquid-cooled models, which had been expressly designed as mechanically quiet for discerning listeners.

A common problem among single processor G5s was the cyclic expansion and contraction of a metal plate soldered to the Logic Board connecting all eight of the RAM slots. Eventually, this can cause the computer to no longer detect the RAM, and refuse to boot. Fixes for this include having the plate re-soldered, or exposing the other side of the Logic Board to heat from a heat gun. The latter option is far easier, since it requires neither soldering nor the removal of the Logic Board from the computer.

All 2.5 GHz and 2.7 GHz dual processor models and the 2.5 GHz quad-processor model had a liquid cooling system that consisted of a radiator, coolant pump, and heat exchangers bolted to the processors. The cooling system was made byDelphi Automotive, a formerHarrison Radiator Division ofGeneral Motors. This was a bold step for Apple, and should have allowed the use of very fast processors, giving Apple an advantage in both performance and reliability, but the system turned out to be subject to coolant leakage, made worse by the system's use of GM Dexcool coolant, which is more corrosive than regular automotive coolant.^[17] If not caught in time, the leakage could destroy the processors, logic board, power supply unit, and even corrode the aluminum casing itself. While leakage was sometimes detectable by drops of green coolant in or beneath the machine, in many^[vague] machines the seepage is so slight that it was almost impossible to detect without dismantling the entire computer. Only the 2.7 GHz model was equipped with aPanasonic liquid cooling system which was much more reliable.^[17]

The liquid cooling system fits into the case where the heat sinks would normally go, so there is no easy way to distinguish the liquid-cooled versions from the air-cooled, although most, but not all,^[vague] of the liquid-cooled machines have a sticker inside warning about the possibility of leakage.^{[citation needed]}

WhenP.A. Semi announced the preliminary pre-production plan ofPWRficient processor,^[18] there had been persistent rumors that Apple would prepare for its use in its professional line of personal computers.^[19]

In 2006,The Register reported thatP.A. Semi had formed a tight relationship with Apple, which would result in P.A. Semi promptly delivering processor chips for Apple's personal computer notebook line and possibly desktops.^[20] Even in 2006, Apple did not have a laptop version of the G5 processor. The processor that would run the personal computers was P.A. Semi's preliminarily proposed processor,PWRficient 1682M (PA6T-1682M). The version that would be sampled for pre-production at third quarter of 2006 was a 2 GHz, dual-core CPU with two DDR2 memory controllers, 2 MB of L2 cache, and support for 8 PCI Express lanes. The sampled chip also has lower heat intensity than Intel'sCore Duo, which gives off 9–31 W under normal load.

According toThe Register article, P.A. Semi executives believed that they were all but assured of winning Apple's contract, and CEODan Dobberpuhl thought that Apple's hints of moving to Intel were just a persuading tactic. At the time, the companies were working for PWRficient software.

Despite the advantages of more compatible architecture, Apple moved to the Intel architecture officially for 'performance-per-watt' reasons. However, P.A. Semi would not be able to ship its low-power multicore product in volume until 2007, which, combined with P.A. Semi's status as a start-up company, seems to have been the final blow to the development of Power Mac computers. However, it was also speculated that Apple switched to Intel processor because Apple could no longer abide the constant delays in performance ramp up,^[21] desired nativeWindows compatibility, or it was Apple's strategy to shift its business focus away from desktop computing toiPod (and subsequentlyiOS) development.

Apple acquired P.A. Semi in 2008,^[22] using P.A. Semi's engineering resources to develop ARM CPUs for theiriPhone,iPod Touch,iPad, andApple TV product lines; and would go on to eventually come full circle withthese designs replacing Intel chips in Macs in 2020.^[23]

The PA6T-1682M processor would later be used by theAmigaOne X1000 personal computer.

Supported macOS releases

OS release	Mid 2003	Late 2004	Early 2005	Late 2005
10.2 Jaguar	10.2.7	—	—	—
10.3 Panther		10.3.4	—	—
10.4 Tiger				10.4.2
10.5 Leopard[Note 1]

Timeline of Power Macintosh, Pro, and Studio models v t e
See also:List of Mac models

• List of Macintosh models grouped by CPU type

Wikimedia Commons has media related toPower Mac G5.

• Ars Technica: Inside the PowerPC 970
• Ars Technica: A Brief Look at the PowerPC 970
• Ars Technica Review: Power Mac G5 Dual 2.5 GHz
• Forevermac.com: The Power Mac G5 Quad Core 2.5 GHz

• Macintosh towers
• Power Macintosh
• PowerPC Macintosh computers
• Macintosh case designs
• 64-bit computers
• Discontinued Apple Inc. products

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