March 19, 2019
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Manufacturer: Apple

Power Mac G5 Dual 2 GHz
November 11, 2003 | Jean-Luc Dinsdale

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Inside - the guts

The Insides
The heart of Apple’s new systems are IBM’s new, POWER4 processor architecture-based PowerPC 970 chips. The 64-bit chip has been designed to access more memory and handle much larger chunks of data than the G4’s 32-bit architecture. In theory, a 64-bit chip can handle up to 18,400,000,000,000 megs of RAM, making the 512 megs that come with the unit look puny. On top of the increased RAM handling, the G5 chip features a large number of improvements, from increased clock speeds, instructions per cycle, floating point units, and integer units. Also increased are the chip’s L1 and L2 caches, which have both doubled. According to Apple, the new chips blow away the competition and promise to go even further in future iterations.

However, an improved CPU can’t run the show alone. Backing up the speedy new chip is a totally re-designed system architecture that takes advantage of the fastest components available. Feeding each G5 chip is a dedicated 64-bit frontside DDR bus that is split down the middle with two, single-direction data path – one each for data flow to and from the processor, allowing for uninterrupted data flow. The frontside bus runs at half the speed of the processor, a huge boost from the G4’s 167 MHz bus limit. On top of that, Apple’s previous dual processor models shared the same frontside bus, while, in the dual G5, each processor has its own bus, allowing data flow to reach speeds of up to 16 GBps.

The G5 uses 400 MHz, 128-bit DDR SDRAM as its memory. The memory bus accesses two banks of memory cards simultaneously, doubling the data transfer speed. The bad news, however, is that users need to install RAM in pairs. The mid- and high-end G5s feature four slots on each bank, meaning an 8 GB RAM limit with today’s RAM technology, while the low-end G5 tower has half the RAM slots, and can only hold four gigs. The G5’s new system controller also ensures that there is no dbottleneck as data flows through the various parts of the system.

Also improved are the computer’s AGP and PCI cards, its hard drives, and all its input/output systems. The new G5s feature AGP 8x Pro video card slot, for use with ATI and NVIDIA's new(ish) 8x AGP graphics cards. The “Pro” delineation means that the AGP slot is equipped with power for Apple’s ADC-equipped monitor. The PCI slots have been upgraded to the faster PCI-X standards. The mid- and high-end G5 models feature two 100 MHz PCI-X card and one 133 MHz PCI-X card for only the most sophisticated PCI cards out there (the low end model still runs on four 33MHz PCI slots).

The new G5’s hard drives have also been updated, with the new systems relying on Serial ATA hard drives. The systems contain two SATA-150 channels, meaning each system can pump 150 MBps of info into and out of the drives. Sadly, users can only put one drive on each channel, meaning the current crop of desktops will max out at two internal hard drives. The switch to serial ATA drives also means that users upgrading their systems won’t be able to yank out their drives from older systems and plop them into the G5. And no, parallel-to-serial adapters don’t work in the new G5s.

Finally, all of the desktop’s I/O systems have been updated. The new G5 desktops sport both Firewire 800 and 400 ports, Gigabit Ethernet, USB 2.0, analogue sound in & out, and the new, pro-level Sony/Philips Digital Interface (S/PDIF) for high-quality, digital audio output and input, another first for Mac users.

Power users will be glad to see such dramatic improvements in the Power Mac line. The combination of the 64-bit chips and the new system architecture, combined with the fastest RAM, AGP & PCI cards readily available, make the G5 a greatly improved and speedier system than its poky G4 predecessors, at least on paper. How does the new system actually compare in real world tests? Read on to find out.

The Bottom Line
Although comparing different processor classes is like comparing apples to mozza balls, a computer review is worthless without a battery of benchmark test results to back its claims. While I didn’t have the luxury of benchmarking any of the mirrored-drive G4s that power our office, I was able to compare the new G5 with the other two Macs we have lying around the house – a first generation 400 MHz G4 desktop and a 667 MHz G4 PowerBook. Comparing a first generation G4 with a first-gen G5 will demonstrate the great differences between the two classes of chips and demonstrate exactly how far the new chips have progressed.

We ran the older G4s and the new dual G5 through a series of five performance tests to see how well the machines would hold up. The tests are principally designed for the professional Mac users whom Apple is targeting with this unit. Being a gaming website, we were tempted to simply run a series of games through the unit and report back the frame rate; however, the graphic designers, video editors, 3D artists, visual effects compositors and scientists whom rely on the best machines available, will probably not be buying these units with the sole intention of snickering at BloodRayne’s tight leather pants.

All tests were run under OS X 10.2.8, with additional testing, as indicated, in Apple’s new OS X 10.3. All three computers were equipped with 512 megs of RAM. All tests were run with with a minimal number of drivers loaded, and, where applicable, all settings were set to high. Unfortunately, only some of the applications used for benchmarking have been optimized to take advantage of the chips’ 64-bit architecture, while other applications have been optimized for multiprocessor environments – as a result, while the tests reported here are a good gauge of the dual G5 in a working environment, some of the results reported here might not adequately represent the full power of the G5 computer.


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