Under the Desktop: Looking at the Next Generation of Macintosh
The dust is only now settling in the wake of Apple's announcement last week of forthcoming high-speed Power Macintosh G5 desktops. A debate now rages online about how fast is fast and the validity of abstract benchmark tests when comparing different families of processors and diverse platforms. "Whatever" will be the response of most creative professionals, especially those who use Windows!
While the determination of the models' performance must await their release in September, Apple CEO Steve Jobs and third-party software vendors offered some impressive demonstrations using professional graphics applications at the Apple Worldwide Developers Conference keynote. Regardless of the final outcome, certainly, their improved performance will be encouraging to content creators wanting to maintain their connection to the Macintosh platform.
The machines will feature a new aluminum style (see Figure 1) and cost from $1,999 to $2,999, with each configuration including a built-in SuperDrive providing DVD authoring. More ordering information can be found at the Apple Store.
Figure 1: There's no either/or when it comes to Apple's new retro case design. It's spare and very aluminum (dare I recall the 1980s industrial chic look?). Notice that there are ports in the front for quick and easy access to USB 2.0, FireWire 400, and audio ports. Be sure to budget enough for a small vacuum cleaner to keep the grille-work clear of dust and lint.
However, there is a significant difference between the low- and high-end models and if you're planning a purchase you should keep that in mind. To put those distinctions in focus, here's a look at some of the technologies offered in the new Mac line.
Tower of PowerPC
To no surprise, the new desktop models will run the 64-bit PowerPC 970 processor, dubbed the PowerPC G5, designating the fifth generation of the family. I took a look at some of its features in a column last October following its announcement by IBM. The 970 combines technologies from the familiar PowerPC G4 chip as well as from its POWER4 heritage, a very-high performance architecture used in servers and clustered computing applications.
In addition to the improved processor performance, the new models will incorporate a variety of system-level technologies sure to become checklist items for future mainstream content creation-class computers, including new standards for expansion buses, high-performance memory bus architectures, and support for advanced graphics cards and serial storage.
The new G5 processor architecture will improve performance with graphics apps through three primary changes to the older G4 layout: faster clock speeds, support for more memory, and a faster and better way of moving data between the processor and memory.
As I mentioned last fall, the G5 processor uses a variety of ways to boost its clock speed, the rate that operations are performed by the processor and the other components of the system. The question at that time was how fast would the chip run. The current top speed is 2 GHz, which is a gain from the 1.42-GHz speed of the current top-of-the-line -- and heading towards obsolescence -- Power Macintosh G4 (FireWire 800) model. Steve Jobs and an IBM executive said the production goal was to raise the speed of the G5 processor to 3-GHz during the next 12 months.
In addition, the G5 models will accommodate four times the memory of G4, up to 8 GB of 400-MHz DDR (double data-rate) SDRAM. This will improve the performance of graphics applications that want to be able to hold lots of items in memory, such as the image being edited, an Undo version, and maybe another image on the clipboard; and that list doesn't count the memory usage by processes from other programs running in the background.
In addition, the memory controller can address two DIMMs at once, helping to move data in and out of memory quickly. While these banks can physically hold the older 333-MHz DIMMs used in the G4 desktop machines, you will want to use new, faster memory modules for your G5 system.
Figure 2: This arty image, lifted from Apple's marketing pages for the new Power Macintosh G5, shows a pair of G5 processors at the top, each communicating separately with the system's new memory controller chip. To the right are the banks of DIMM slots and to the left is the AGP 8X Pro card. Readers should note that it's not illustrated to scale, nor do the connection channels give off a blue glow.
Changes in the way the G5 moves data between the processor and memory modules will help remove a significant performance bottleneck found in earlier machines. In techno-speak, a processor's face to the world is called a Frontside Bus (see Figure 2). The G5 supports a 64-bit bus running at speeds up to 1-GHz (the frontside bus speed depends on the speed of the processor), and according to industry analysts, this will be the fastest such bus offered in a desktop system for the rest of the year if not longer.
For the top-end models with dual processors, each chip will have its own frontside bus, instead of sharing a single channel. For more information about this bus architecture see Apple's G5 architecture page.
Of course, attendees at the keynote address wondered how fast these machines would perform, especially with content-creation applications.
Steve Jobs pointed to the results of benchmark testing performed by Veritest, an outside lab. Those test suites conformed to the Standard Performance Evaluation Corp. (SPEC) benchmark system. You can see the results on Apple's G5 performance page. Jobs proclaimed the G5 as "the fastest personal computer in the world."
This claim got every PC geek on the Internet up in arms and Mac fans responded. ExtremeTech.com provided a good roundup of the brouhaha. The PC advocates pointed out various inequities in the test parameters, and questioned the results of the tests.
To be fair, each system should run a suite of test applications that are optimized for the particular system. And it seems clear that wasn't followed to the letter for these tests.
At the same time, vendors of graphics tools demonstrated the performance of their Mac and PC versions running on a dual G5 system and a dual 3-GHz Intel Xeon system, respectively. The applications included image editing (Adobe Photoshop), 3-D animation, and audio processing. They reported that on the whole, the G5 machines ran their products twice as fast as comparable Windows systems.
That's a significant change upwards, especially when we consider the declining performance of the Mac over PCs over the past several years. Both Mac and PC content creators have given me grief when I've pointed out the Mac's performance deficit and that there could be other valid reasons beyond speed to use a Mac (or perhaps now a Windows machine).
For example, one test listed on Apple's page described a series of tests performed with Photoshop, running a 600-Mbyte image through "45 commonly used actions." Both platforms had 2 GB of RAM and were able to put the files into memory. The dual G5 ran the test suite twice as fast as the dual Xeon system. At the keynote, Adobe Vice President of Engineering Greg Gilley confirmed that result. "Our customers will love this box," he said.
Still, some people questioned the vendors' testing, claiming that these real-world performance tests may have highlighted the advantages of Apple's new architecture. And that could be so. After all, improving performance is one of the things a software update is supposed to do and undoubtedly vendors would love to get professional Mac users into an upgrade cycle.
However, these third-party vendors have little to gain by picking sides on the platform debate. Software companies that really support multiple platforms try to make sure that their product will run the best it can regardless of the platform, even if that level of support can vary at times.
The new processor and memory architecture aren't the only technologies incorporated into the new Power Mac G5 designed to optimize performance. Heading downstream from the processor and memory system -- known in the logic board industry as "south," with the processor being "north" -- there are many sites of interest, such as the graphics port, storage, and expansion slots.
HyperTransport. The new Macs, like computers based on Advanced Microdevices' Opteron processor, use the high-speed HyperTransport bus to connect the various southern system components. The standard was created by AMD as a replacement for the PCI bus, but now its development is controlled by a non-profit industry group called the HyperTransport Consortium. Content creators might compare this history to the development of FireWire, which passed from Apple to the 1394 Trade Association.
The HyperTransport standard supports much higher throughput speeds than PCI. It also can better arbitrate between the great speed of the processor and the slower speeds of connected devices. As the speed of the processor increases, the whole system becomes more vulnerable to little delays, or latency problems, which is the time it takes for the system to recover and then process a missed piece of data. The best performance for a system will be gained when everything works correctly in precise coordination, even if that means that certain parts run more slowly than their possible speed.
AGP 8X Pro. One gripe about the Power Mac G4 was its paltry support for top-level graphics cards. The G5 models offer an 8X Pro slot, which offers twice the performance of the previous interface. However, Apple demonstrated the G5 with the latest flavors of the mid-level consumer graphics cards instead of the workstation cards. It remains to be seen if the G5 supports the full Pro specification.
PXI-X bus. Depending on the model, the new G5 comes with three PCI-X slots. According to the PCI Special Interest Group, the slot is the "evolutionary" step-up for the long-standing PCI interconnect, offering up to eight times the bandwidth of the current PCI bus.
Serial ATA drives. Instead of connecting internal hard drives with the familiar ATA interface, the new Macs will use the Serial ATA standard. This interface is beginning to replace the ordinary parallel ATA in PCs and uses a simpler, thinner connector. The interface is used for both very high-capacity drives with slower speeds as well as the latest high-performance mechanisms.
To keep all of this stuff cool, the G5 enclosure features a complicated system of air channels and fans (see Figure 3). The case is divided into four zones, each with its own set of independently controlled fans. The computer checks the temperatures and adjusts the speed of each fan to supply just the right amount of cooling to the right place. While there are nine fans in the case, the machine is much quieter than the previous G4 machine. Jobs said it was 39 decibels.
Figure 3: This illustration shows the air flow through the enclosure, blue is cold and pink is hot. There are four zones, although the bottommost level -- which holds the power supply -- is difficult to see.
More and Less of the Right Stuff
The three G5 models come with identical software packages and a wide range of networking and I/O connectors. However, there are significant differences with the entry-level model.
The lowest-priced version comes with a 1.6-GHz G5 processor with an 800-MHz frontside bus. This is still plenty of performance. However, the model removes two important features for professional content creators: It supports "only" 4 GB of RAM and it has three ordinary 33-MHz PCI connectors instead of the PCI-X slots.
The middle and top models both support 8 GB of memory and three PCI-X slots, one is a 133-MHz slot and two run at 100-MHz. For more information about the details of the models see Apple's G5 specifications page.
I recommend that professional content creators look first at the mid-range or dual processor model rather than at the entry-level version. Memory is important to content creators and while 4 GB is twice the current level it's still half of what you could have with the higher-priced model.
In addition, though some readers may feel that the built-in Gigabit Ethernet and FireWire 800 offer plenty of expansion options for future high-speed peripherals, the performance available over the PCI-X bus could prove to be important in the near future. New lines of inexpensive, fast external storage could use the faster bus and bandwidth.
Finally, the top-of-the-line dual-processor model will offer the most performance, and the best chance to improve your productivity. It also should hold its value the longest.
In a bit of irony, Apple will return to selling both single- and dual-processor models of the Power Mac G4 that can boot both OS X and Mac OS 9, which may still be important to your workflow. The company dropped that dual-boot capability with the current FireWire 800 models introduced in January. Naturally, the G5 models can't boot into OS 9.
Of course, it's easy for me to make up your hardware budget. As the saying goes: "Man is often generous -- with someone else's money." Perhaps now's the time to look at your workflow and consider if it could benefit from a speed upgrade.
Read more by David Morgenstern
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