Under the Desktop: All PowerPC to the People
Performance enhancement is often on the minds of content creators, whether from application and system software, or in hardware, such as the graphics display card, storage devices, or memory configuration. Each component shares the load, which can either improve or impair the overall speed of your system. Considering the compute-intensive applications and large file sizes common to creative work, system performance is critical to the daily workflow of most designers and producers.
Of course, a significant part of the performance picture is the processor, so I looked forward to the processor industry's annual powwow, In-Stat/MDR's annual conference, Microprocessor Forum, held in San Jose, Calif. There, several manufacturers discussed the future gains in performance of chips destined for high-end graphics workstations. Still, the operative word here is "future," which in this case means at least a year or even longer.
Known in the trade simply as MPF, the conference often features the introduction of new chips for all types of applications, from mainframe computers to $300 PCs, as well as the low-power processors found in consumer digital devices, such as phones and handheld devices. In addition to great up-to-the-minute information, attendees receive an eBay-worthy industry collectable: a portfolio with actual processors embedded in the cover (see figure 1).
Figure 1: On the left is the latest MPF portfolio, while the one on the right hails from 1996. While I appreciate the upgraded graphic design of the current version, there's a level of grandeur in a book literally covered with chips. The 2002 version has but three small ones. Squinting hard at the right hand portfolio, you will find that the big gold chip in the middle of the top row is a POWER2 from IBM.
For content creators on the Macintosh platform there was big news indeed: IBM introduced the PowerPC 970, a chip that appears destined for the next-generation Apple servers and Power Macintosh desktops. The reason for the equivocation is that IBM and Apple are completely mum on the subject. No surprise there. Despite the official silence, it's clear that this processor is slated for a future Mac.
The announcement is perhaps the most important piece of processor news since the introduction of the PowerPC G3 in 1997 and has fueled plenty of speculation in the Mac community over the 970's origins and performance potential.
Before moving into the specific products, we would do well to briefly discuss 64-bit processing, since the technology is a source of some hubbub.
All of today's desktop computers use a 32-bit processor, whether Mac or Windows. The 32-bits refer to length of the chip's addressing and instructions. These processors can handle a maximum of about 4 gigabytes of memory at a time (4,294,967,296 bytes, but who's counting?). There are ways of extending this limit, but it's tough. Yet, most of us rarely consider 32-bit addressing much of a drawback, since until recently, the cost of 4 GB of RAM was astronomical, and our operating systems and applications are designed to run within these constraints -- we just accept them. But as mentioned in previous columns, content-creation applications can certainly use more RAM and speed.
However, some high-end servers and workstations used in the CAD (computer-aided design) engineering and scientific visualization market run 64-bit processors, which can handle much more RAM and larger data sets. The 64-bit addressing can tackle very large operations, such as rendering each pixel of a huge image, or by mapping lots of memory to hard drives in a virtual memory scheme.
According to chip gurus, a 64-bit processor could theoretically manipulate up to 16 exabytes of data. However, ignoring the pie-in-the-sky specifications, these workstations can easily use 8 GB or more RAM in real-world applications.
These workstations and their associated processor architectures are available from a variety of vendors, including HP (PA-RISC), IBM (POWER), SGI (MIPS), SUN Microsystems (SPARC); Intel and HP teamed up to create the Itanium processor, a.k.a the IA-64, distinct from the IA-32 family that includes the 32-bit Pentium 4 and Xeon processors. Most of these machines use their own homegrown 64-bit-savvy OS (some version of Unix) and applications must be coded specifically to support the 64-bit capabilities.
Mac My Day?
The PPC970 is significantly different than its forebears. Rather than an evolution of the current lines of PowerPC architecture, it's a 64-bit processor based on IBM's POWER architecture used in the company's Unix workstations and servers. The 970 is not on the old PowerPC design roadmaps (see figure 2), still, it can run current 32-bit applications.
Figure 2: This roadmap is from an earlier era when Apple, IBM, and Motorola formed a consortium to create the PowerPC processors. It shows the first four generations of PowerPC designs. The top bullet point mentions that work at the Somerset Design Center in Austin, Texas, would be expanded -- it was taken over by Motorola when the alliance split up in 1999.
The processor also combines a SIMD (single instruction, multiple data) vector engine for accelerating multimedia. From the description, it sounds suspiciously like the Velocity Engine found in the current PowerPC G4.
One way that chip vendors increase frequency (the chip's internal speed) is by breaking down a job into sets of smaller ones, thereby increasing the number of steps needed to do a task. This ordered series of steps is called a pipeline. This sounds as if it would be less efficient, however, since the chip marches to the strict beat of a clock, the more little things that can be done in a single cycle sometimes the better. Intel has done this to great effect in the Pentium 4.
The 970 will run at a faster clock rate than the current PowerPC G4 and IBM's specification mentioned 1.4-GHz and 1.8-GHz versions. In addition, these initial speeds could be increased as the chip enters production in the next year. The clock speed will always lag behind the Pentium 4, which currently stands at 3 GHz.
"The 970 makes absolutely perfect sense -- the only question is why did they wait so long?" asked Keith Diefendorff, the former architect of the Velocity Engine at Apple, and now vice president of product strategy at MIPS Technologies. He said that while Apple has done an excellent job of reducing frequency as an issue in the marketplace, the speed of the PowerPC needed to pick up the pace.
More megahertz doesn't automatically mean greater performance when comparing different chip architectures. For example, the PowerPC's RISC architecture does more with each step, and while running at a slower clock rate when compared with the Pentium 4, it can provide equal or better performance. As Diefendorff mentioned, Apple (and now even PC-chip vendors such as Advanced Micro Devices) point to this fact as the "Megahertz Myth."
Some tasks benefit from higher integer speeds, while others can take better advantage floating point operations or multiple processors. Vendors prefer to compare performance with artificial benchmark tests, even though the results may be better or worse when the chip is working in a real computer, with a real application and in your particular workflow.
In his presentation, Peter Sandon, IBM Senior architect, provided a couple of figures for the 970 using the Standard Performance Evaluation Corp. 2000 (SPEC2000) tests for integer and floating point performance. He said a 1.8-GHz 970 rated a 937 and 1,051 for the integer and floating-point tests, respectively; in comparison, according to InStat/MDR, a 2.5-MHz Intel Xeon currently holds 893 and 878 ratings, respectively.
The Velocity Engine can provide even more power to the floating point performance. "The 970 is a floating-point monster," said Peter Glaskowsky, editor in chief of the Microprocessor Report.
In addition, the processor features a very, very fast 900-MHz bus to move data on and off the chip, which is useful for multiprocessor configurations and large RAM caches. It also will have the "elastic" ability to wait a number of cycles for data to arrive -- a necessary feature since most current system buses run way slower than 900-MHz (the current Power Macintosh G4 has a 167-MHz system bus).
It's difficult to know whether the first flavors of 970 will be used in a PowerBook. Analysts at the conference expected the chip first in Apple's Xserve server and in Power Mac desktops. The current G4 chip runs about 30 Watts when really crunching hard on data. My reading of the 970's spec sheet showed the 1.8-GHz 970 will be in the mid-40-Watt range. However, it also includes the current frequency reduction routines to reduce power consumption and heat. The analysts expected later versions of the 970 to be designated for notebooks.
On the Cutting Edge (of Rumors)
The hullabaloo over the announcement (beyond Apple and IBM not talking about each other) dealt mainly with the 970's 64-bit nature and its origins.
The current POWER4 is dual core, meaning that it has two processors inside a single chip (see figure 3). This is different from a dual-processor machine that uses two separate chips mounted on a card, such as the latest Power Macs. The internal communication between the two integrated processors is very quick indeed.
This capability has long been a talking point of Mac rumor sites. Years ago, sources said that dual cores were in the long-range roadmap for the PowerPC. In spite of this, the plans were scrapped as the market changed, as both IBM and Motorola focused their PowerPC efforts into the embedded markets. And today, the greatest use of the PowerPC can be found in automobiles.
Figure 3: This is an engineering diagram of the POWER4 processor. The two processor cores are the blue boxes (what else for Big Blue) at the top, which communicate with the three integrated Level 2 caches in the middle. Below is a fabric switch that can communicate with other processors in a multi-multiprocessing computer. The 970 has a single core and just one L2 on its die.
Several analysts at MPF said with its POWER4 foundation, it was natural evolution for the 970 to gain dual cores. However, that would come in a second-generation design, at the earliest a few years from now.
The outlook is similar for 64-bit computing. While the 970 is a 64-bit processor, the Mac of today is 32-bit all the way and Apple has made no mention of any plans to support 64-bit computing in OS X -- naturally since there wasn't a 64-bit PowerPC on the horizon. Now there is.
"Apple will bring 64-bit mainframe-class part to the high-end desktop," MDR General Manager Kevin Krewell predicted. "For the content creation world, this [announcement] is really something. Apple is getting a real jump on 64-bit addressing over Intel."
However, Diefendorff was of the opinion that Apple would move slowly into the capability. "There's little advantage for Apple to go to 64-bit addressing right now. But it's there. [Higher] frequency is the story here now."
Timing the Market
So, how should Mac users evaluate this announcement? Should we put off all purchases until the new processors arrive? Or look for application developers with 64-bit experience?
Just as it's foolish for speculators to "time" the top or the bottom of the stock market (even though it's tempting to do so), it would be inappropriate for Mac content creators to make the 970 chip a part of purchasing decisions at this time -- a year from now, maybe. If you need a faster machine now, buy one now.
Indeed, I suggest readers consider buying the best that's currently available rather than settling for an older model. That faster machine will provide more productivity for a longer period of time than will a slower, older model. Of course this seems self-evident, but many people end up with a low-end machine because they're on sale, rather than factoring in the long-term productivity to be had from high-end models.
This is especially true with a dual-processor Mac. There's no guarantee that Apple will continue its dual-processor strategy once this new chip hits the streets late next year. The highest frequency processors may be offered in single-processor models, or only in servers. So, the value of a current dual-processor model will hold its value, certainly more than an older single-processor that is still being sold in the aftermarket nowadays.
The same holds true for 64-bit addressing. Until Apple commits to a 64-bit version of OS X, there's no need to even think about 64-bit applications. But I agree, it's nice to dream.
With all that I've said, why do I consider this announcement so important to Mac users?
The PowerPC 970 marks a new trend in desktop processors: the movement of technology from the very high end of the market down towards the midrange, where we graphics professionals live. This bucks the practice of the past five or so years, as processor vendors have focused on the entry-level segments of the market. Or even worse, as we've seen from IBM and Motorola, a concentration on the embedded application market.
The needs of a desktop or workstation processor are different than those of an embedded device. Or a notebook. Or a $300 computer. Or even a $1,500 computer. There was no way that these recent efforts could produce the best possible architecture for our content creation applications.
I'm not pointing my finger just at the PowerPC developers -- the same situation holds true in the Windows camp. I will discuss Intel and AMD's strategy for high-performance desktops and 64-bit computing in my next column.
In the long-ago past, high-performance technology was migrated to mass-market products. This was true for all kinds of devices, from scanners to computers. But the consumer and telecommunications markets appear to have distracted the purveyors of our processor technology, leading them to focus on entry-level, inexpensive products; or vertical applications in devices such as switches.
There's an old Jewish saying: "A goat has a beard -- but that doesn't make him a rabbi." The same is true for microprocessors. Technology should flow downstream, like the PowerPC 970, to the benefit of creative pros.
Read more by David Morgenstern.
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