Dual-core chips: Twice as nice? By Laurianne McLaughlin http://www.macworld.com/news/2005/10/20/dualcoreanalysis/index.php
Dual-processor machines have been a constant part of the Mac landscape since Apple put a pair of 500MHz G4 chips into a Power Mac back in 2000. But that landscape shifted Wednesday when Apple introduced a refreshed Power Mac line built around dual-core chips. Apple¹s Power Macs now feature dual-core 2.0GHz and 2.3GHz PowerPC chips from IBM. There¹s also a dual-core, dual-processor 2.5GHz model, which Apple is touting as the Power Mac G5 Quad. The machines are powered by dual-core processors that IBM introduced in July, shortly after Apple announced it would use Intel-built CPUs in its hardware starting in 2006. And it¹s very likely that some future Intel-based Mac systems will also take advantage of dual-core technology. So what¹s the difference between a dual-core system and one built around dual processors? And more important to Mac users used to hearing that two CPUs are better than one, how will dual-core improve the overall performance of their machines? One chip, two processing units First, the setup: instead of having two processors in two separate sockets on a computer¹s motherboard, a dual-core system has one physical processor in one single socketbut with two independent processing units inside it. This can save space and money. A dual-core chip can also let the two CPUs share memory cache and bus connections to the system, a cost and design advantage. Otherwise, the system¹s hardware looks pretty much the same, whether it¹s a dual-core or dual-processor setup. Dual-core may be a new addition to the Mac platform. But on the PC side, Intel and AMD have been supplying PC makers with dual-core chips in recent years. It¹s been a way for chipmakers to deliver high-performance without high heat. For that reason, a dual-core chip makes a lot of sense for Apple. Today¹s dual-processor setups pose several big problems, starting with the fact that the two chips throw off a lot of heat, requiring huge heat sinks and special cooling systems. Thus a dual-processor set-up limits Apple¹s design options, while boosting costs. A dual-core chip, on the other hand, potentially frees up Apple to create brawny machines that will be smaller than today¹s Power Mac G5 models, says Roger Kay, president of market research firm Endpoint Technologies Associates. ³Most users would rather have the same power in a smaller system,² Kay says. ³Unless you need extra space for cooling, you can get rid of it.² Performance boosts It will take some time for those size advantages to appearthe Power Macs introduced by Apple Wednesday retain the 20.1-by-8.1-by-18.7-inch dimensions of the previous model. However, Apple is already taking advantage of the fact that a dual-core chip fits two CPUs in the space of a single chip; instead of shrinking the size of the box, Apple instead announced the Power Mac G5 Quad, which fills the space that once held two CPUs with two dual-core chips, for a total of four processing units. By combining two processor cores on a single silicon chip, Apple says a dual-core processor can deliver double the computational power of a single-core CPU. In the case of the Power Mac G5 Quad, applications are able to take advantage of four 1MB L2 caches, four 128-bit Velocity Engines, and eight double-precision floating-point units, boosting performance over a single-core, dual-processor system. Still, today¹s dual-core chips aren¹t perfect yet. So chipmakers are working on new generations of higher-performance, lower-power dual-coresincluding Intel, Apple¹s CPU supplier starting next year. One problem with many of the dual-core chips now available: Intel and AMD chips can¹t run as fast as a single core processor (made using the same manufacturing process and the same design architecture as the dual-core chip), because they¹d run too hot and require too much power, says Kevin Krewell, editor-in-chief of the Microprocessor Report. Today¹s dual-cores aren¹t running at their top clock speed potential. So some apps, including many games, still run faster on a PC using single core chip. Mac users have to wait for testing of the new Power Mac G5s to see how IBM¹s dual-core processors fare in this regard but it¹s interesting to note that the new dual-core G5 processors top out at 2.5 GHz, compared to 2.7GHz for the previous top-of-the-line single-core G5 chip. With dual-core-powered PCs, users see the most performance gains when using applications that have been multi-threaded to take advantage of the two cores. That¹s a promising development for Mac users since many of their programs have already been rewritten to recognize and take advantage of multiple CPUs, thanks to the abundance of dual-processor Power Macs. And those Mac apps will recognize and tap into the benefits of the two CPUs whether you¹re using a dual-processor machineor a dual-core machine. Because of OS X¹s symmetric multiprocessing, the operating system itself can also direct individual tasks to different cores. This means one process or application can be directed to one core, and a different task to another core. Other programs that haven¹t been multi-threaded will run on a dual-core system just as they would a dual-processor machine; they just won¹t take full-advantage of the benefits. Many mainstream PC applications haven¹t been released in multi-threaded versions yetbut the ones that have tend to be in the arenas of creative arts and science and engineering two markets where the Mac is extremely popular. ³Heavy-duty applications, such as those that use video, will benefit from a dual-core chip because the system can throw more horsepower at the application or throw one core at the application, and devote the other core to maintaining system tasks,² says Shane Rau, Program Manager for PC Semiconductors at market research firm IDC. Looking ahead It¹s fair to say dual-core represents the way of the future for the major chipmakers, who are adopting the design strategy to keep making significant performance gains. ³Just increasing clock frequency, which has driven much of the performance increases over the last decade, has become unattractive due to the extra power requirements,² Microprocessor Report¹s Krewell says. ³Slower clocked dual-core processors can still offer performance increases with multi-threaded applications.² Dual-core technology really gets interestingand really takes a big step ahead of dual-processor systemswith Intel¹s next-generation processors, expected in the second half of 2006. They¹re designed from the ground up to consume less power and run much cooler. (These low-power dual-core chips are code-named ³Merom² for notebooks and ³Conroe² for desktops.) While the exact timing and details of Apple¹s transition to Intel chips remains under wraps, it¹s safe to assume that the changes to the Power Mac system signal a long-term interest in dual-core technology on the part of Apple. And that¹s fortunate since Intel intends to make its product line (except for Celeron chips, designed for the lowest- cost PCs) completely dual-core by the end of 2006. AMD will likely follow a similar strategy, Krewell says. You are a subscribed member of the infowarrior list. Visit www.infowarrior.org for list information or to unsubscribe. This message may be redistributed freely in its entirety. Any and all copyrights appearing in list messages are maintained by their respective owners.
