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CPUs : A Basic Primer | View information about CPUs : A Basic Primer within our Technology Website Directory section by reviewing this area of our website. We provide a wealth of information online to help our visitors become better informed about Computer Buzz. |
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CPUs : A Basic Primer
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Now that Apple has dumped Motorola as the supplier for their CPU chips, the only two major manufacturers of central processing units (CPUs) left standing are Intel and AMD. To be sure, Motorola is not completely out of the business, and Sun Microsystems still designs and makes their own SPARC chips, but those are small potatoes in the grand scheme of things.
Except for a few geeks who build their own computers from scratch, nobody cares about buying individual CPU chips. But when shopping for a new or used computer, few things are more fundamentally important than the CPU that powers the box. For your edification, Computer Buzz has assembled a few brief topics that you might want to consider when shopping for your next desktop or laptop.
(Historical note: Adjacent image shows ancient Zilog Z80 CPU, considered by many to be the chip that started it all.)
Official Website: www.AMD.com
Official Website: www.Intel.com
Official Website: www.Motorola.com
Official Website: www.Sun.com
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Multi-core Chips
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The hottest buzz in the computer subculture these days revolves around quad-core CPUs. Quad-core simply means that four processors have been squeezed onto one physical chip (or that the motherboard contains two dual-core chips). Multiple processors are not a new idea. In the early 1990s, Be, Inc introduced the BeBox computer running the proprietary BeOS that allowed eight or more CPU chips to run concurrently. Sun Microsystems was installing modular dual processors in their Unix workstations more than a decade ago. And Apple began offering dual G4 CPUs in their desktops shortly after the turn of the millennium. WinTel PCs have lagged behind and have just recently started appearing now that Windows is finally able to take advantage of them.
Apple was the first computer company to go exclusively with dual-core chips. Most Windows machines now come with at least a dual-core option, but there are still plenty of conventional single core chips in the pipeline, and low-end and/or off-brand entry level machines with a single-core CPU will still be available for some time. To get the most out of a multi-core CPU, your favorite software programs have to be written so as to take advantage of it. Some are; some aren't. Most action games and video editors make good use of multi-cores; most word processors could care less.
When it first appeared last year, Computer Buzz labs considered AMD's quad-core Phenom 9 chip to be a shade faster than Intel's equivalent Core 2 Extreme QX. But Intel soon caught up with and passed AMD with its Core 2 Quad Q6600. Then came the even faster Intel Core 2 Extreme QX9650, and more recently the faster still QX9770. All of these CPUs are so fast that most users could not possibly notice the difference.
Apple was also first to jump on the quad-core bandwagon with four versions of its Mac Pro desktop model featuring two quad-core Xeon/Core 2 Quad chips for a grand total of eight cores! AMD has responded with its four-core Phenom CPU. Alas, as of 2008, there are few enough applications that can benefit noticeably from dual-core CPUs and desperately few that are yet written for quad-cores. We can still cast our memory back to the early 1970s when we shelled out big bucks for the latest and greatest "quadraphonic" stereo system and then waited...and waited...and waited for the first four-channel records to appear. (I think I still have both of them.)
(Adjacent image shows AMD Athlon 64 FX dual-core CPU.)
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32 or 64 Bits?
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The earliest personal computers from the late 1970s were 8-bit machines. In the '80s that changed to 16 bits. The large majority of all PCs in the world today are 32-bit machines. Sun Microsystems has been producing 64-bit SPARC chips for more than a dozen years now, and the transition in the broader industry, though far from complete, is well under way. All of Intel and AMD's high-end chips now support 64-bit instruction sets.
If you have a 64-bit PC, you will first need to install a 64-bit operating system in order to take advantage of it. Mac OSX and Windows Vista can do so, as can Sun's Solaris version of Unix. And there are several versions of Linux that are published for 64 bits as well as the standard 32.
With your 64-bit hardware and OS in place, you will then need to find suitable application programs that are specifically written for 64-bit processors. At the moment, those are few and far between. We expect that to change, but not overnight. Patience is a virtue.
(Adjacent image shows AMD Opteron 64-bit CPU.)
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Clock Speed
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Clock speed is probably the most used and most quoted measure of a CPU's ability to crunch bits and bytes in haste. And it is unquestionably the most misleading, inaccurate and unreliable. Clock speeds are meaningful only insofar as they pertain to chips in the same general category by the same manufacturer. It's sort of like trying to compare automobile performance by considering only horsepower figures. The numbers notwithstanding, 350-HP Cadillac will NOT outrun a 300-HP entry level Corvette. But a 400-HP 'Vette will certainly outrun both of them.
That caveat holds true enough for the usual offerings of Intel and AMD, but it is especially true of comparisons between CISC (complex instruction set chips, primarily produced by Intel and AMD) and RISC (reduced instruction set chips, manufactured primarily by Motorola, IBM, and Sun, and formerly used in Apple's Power Macs; still used in Sun's SPARC servers and workstations) architectures. Because of basic design differences, a 1-MHz RISC machine would easily equal or outperform a 2-MHz SISC box. Problem is, megahertz for megahertz, RISC chips use more energy and run hotter that the CISC chips, and their nominal clock speeds tend to lag behind their CISC contemporaries. Computer Buzz has a couple of Sun SPARC dual-processor machines in our Dallas lab, and we use them in place of space heaters during the winter.
Now, a 2.66-MHz CPU will outrun a 2.33-MHz version of that same chip, everything else being equal. But consider the fact that tests have shown that the average human being can not detect a performance increment of less than about 20 percent in a PC. And many apps, like word processors, are already running so quickly on low-end hardware that a significant increase in clock speed is likely to go unnoticed. Likewise, apps like browsers and email clients are bottlenecked by factors (e. g., online bandwidth) that have nothing to do with CPU clock speed.
(Adjacent image shows Sun UltraSPARC IIi RISC chip clocked at 333 MHz.)
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L2 Cache and Front Side Bus
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Computer Buzz believes that the computer's so-called Level 2 (L2) cache and front side bus (FSB) configuration is often more important than the CPU's clock speed.
The L2 cache is a dedicated part of memory that is located on the CPU chip. It speeds things up by continuously storing recently fetched data (usually off of the relatively slow hard disk) so that it is immediately available to the processor when (and if) it is needed again, whether in a few seconds or milliseconds. More is better, especially if you have an Intel CPU, because it will benefit more than an AMD chip from a larger cache due to the way the two access memory. So again we see that, like clock speeds, L2 cache sizes are not directly comparable between different chips or chip makers.
The front side bus speed determines how quickly an Intel CPU can communicate with the memory controller which is located elsewhere in the box. Faster is better. The early Core 2 Duo chips had an FSB that ran at 1066 MHz; the latest ones are up to at least 1333 MHz. We expect more increases any time now. AMD puts the memory controller right on the CPU, so the FSB never comes into play. Again, the parameters are such that the speed of the chips is not comparable.
(Adjacent image shows Intel Core 2 Duo 64-bit, dual-core CPU.)
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Top of the Line CPUs
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So, when money is no object, what CPU do you choose for maximum performance? Right now the fastest single chip in the world is Intel's four-core Core 2 Extreme QX6850 running at a clock speed of 3 GHz and sporting a 1333-MHz front side bus and an 8-MB L2 cache.
Until AMD's much-anticipated quad-core Phenom chip actually hits the shelves, that company's fastest gizmo is a motherboard containing two Athlon 64 FX chips. It's more expensive than the QX6850, and it generates more heat, but it also generates more computational horsepower in most situations. AMD claims that you will soon be able to remove the Athlon chips from that aforementioned motherboard and replace them with two quad-core Phenom chips, thus giving you an eight-core monster that really screams!
(Adjacent image shows Intel Core 2 Extreme 64-bit, quad-core CPU.)
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The Bargain Basement
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There are still some older CPUs floating around, and they can usually be found in off-brand, bargain-basement PCs that are perfectly serviceable for most everyday purposes in the home. These include such venerable chips as:
Intel Celeron D
Intel Pentium D
Intel Pentium M
Intel Pentium 4
AMD Athlon 64 (single core)
These are going to run slower and hotter than most of the newer chips, but if your computing needs are not too terribly sophisticated, they will represent your best bang for the buck. Don't plan on keeping them for ten years, however, because their useful days are numbered.
And let's not forget all the Motorola-powered G4 and G5 Macs that are still around on eBay. Apple and most of its supporting software companies still support the PowerPC architecture, and those units are some of the best bargains to be had these days.
(Adjacent image shows Intel Pentium IV CPU.)
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