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This chapter is from the book

Perhaps the most crucial part in any computer, the CPU serves as your rig's brain

Figure 3.1Figure 3.1 We used a Pentium 4 3.2GHz in the 2003 Dream Machine. At the time, it was undeniably the fastest CPU on the planet, and we overclocked it to make it even faster!

One of the most important questions you're going to face when spec'ing a new dream PC is, "Which CPU do I buy?" This question immediately raises a second question—"Intel or AMD?"—which in turn raises a whole host of questions on which motherboard to buy and what kind of RAM to use. And then there's the issue of raw speed: "How much clock speed does one really need?"

Before we delve into the particular products that each CPU company has to offer, let's take a quick look at the first thing on everyone's mind when choosing a processor: the mighty megahertz question.

Megahertz: Does It Really Matter?

Watching the stunning increase in Intel clock speeds over the years, many of us have been conditioned to think that megahertz is the most important determinant of CPU performance. A 2.4GHz CPU is faster than a 2.2GHz CPU. It's simple math, right?

No, not always. Clock speed can often be a misleading indicator of a processor's actual real-world horsepower. The two leading CPU families—the Intel Pentium 4 clan and the Athlon XP/FX brood—use distinctly different number-crunching strategies that affect overall performance in very real-world ways. Although clock speed is always an important metric of brute strength (especially when comparing two CPUs that share the same architectural DNA), other CPU design factors come into play.

To give you an idea of how different CPU designs can lead to wildly varying performance results, consider the original Pentium 4 (P4). Launched at a speed of 1.5GHz, many people reasonably assumed the P4 would be much faster than the Pentium III, which at the time was hitting a top frequency speed of 1.1GHz. Unfortunately, however, because of core architecture differences between the two chips, the P4 was actually slower in many applications available at that time—this, despite its 400MHz clock speed advantage!

So why the performance drop? One reason is that when the P4 was first released, most applications weren't yet optimized to take advantage of the CPU's special instruction set, code-named SSE2. In due time, software developers would re-code their apps for SSE2, and when they did—boom!—the P4 suddenly showed much better performance. It was a simple matter of waiting for the software to "catch up" to a hardware architecture change. Nonetheless, until those apps were re-coded, they weren't taking full advantage of the P4's particular architecture.

The other culprit that made the P4 look dog-slow when it was released was its lengthy, 20-stage instruction pipeline. Long pipelines help facilitate high clock frequencies, but for many jobs that a CPU might have to execute, they can also lead to performance inefficiencies (and thus bad benchmark results). Maximum PC columnist and chip guru Tom Halfhill explains:

Figure 3.2Figure 3.2 The original Athlon 64 CPU just used a single channel memory interface, but that didn't really affect performance that badly.

A CPU pipeline is like a factory assembly line; it divides work into a sequence of stages. In a CPU, "work" is executing a program instruction. Several instructions can move through the pipeline at the same time, with each instruction in a different stage of completion. During each clock cycle, the CPU can retire the results of one instruction at the end of the pipeline while fetching a new instruction into the front of the pipeline.

Longer pipelines allow a chip to run faster because each stage has less-complicated circuitry. The time it takes for the slowest stage to do its work is the limiting factor for the whole pipeline, so dividing a slow, complicated stage into two or more simpler stages relieves the bottleneck. Super-long pipelines have drawbacks, however. Branch instructions require the CPU to flush partially completed instructions out of the pipeline and replace them with new ones. It's like a factory foreman suddenly ordering an assembly line to make pick-up trucks instead of sedans—the partially completed sedans must be discarded. To avoid this problem, modern CPUs try to predict the outcome of branches. But if the branch prediction stinks, the length of the super-long length of the pipeline can actually hurt performance.

And therein lay the P4's pipelining problem. Many tests—such as those based on office apps—are rife with conditional branches. These tests bogged down in the P4's super-pipelined architecture. The Intel PIII and AMD Athlon XP processors, meanwhile, processed these tests quite handily, despite their clock speed disadvantage. The whole situation was a textbook example of why clock speed isn't the be-all, end-all of performance.

Figure 3.3Figure 3.3 The classic 32-bit Athlon XP CPU was the budget workhorse for several years, but it's fallen by the wayside with the introduction of newer 64-bit Athlons.

But it's now been more than three years since the P4 was introduced. The CPU's branch-prediction logic has improved, and the very clock-speed increases made possible by the P4's lengthy pipeline have more than compensated for the CPU's intrinsic inefficiencies. Now buzzing along at more than double its introductory clock speed, the Pentium 4 is the recognized performance leader. In short, the long pipeline is paying off.

This doesn't mean, however, that an Athlon XP running at 2.2GHz is always going to be a lower performer than a Pentium 4 running at 2.5GHz. Because the Athlon XP's architecture is particularly well-suited to floating-point calculations, the CPU performs very well in floating-point-heavy apps such as 3D games. This means that for many types of a software, an Athlon XP can complete more work in a single clock cycle than could a Pentium 4. The new 64-bit Athlon FX CPUs continue the AMD tradition of doing more per clock cycle than the Pentium 4, so you really can't judge a modern processor by its clock speed.

So that's our spiel on CPU theory! It should give you a good foundation of knowledge as we move on to discussions of specific Intel and AMD CPUs.

Kick-Ass Construction Tip

The socket designed to hold your CPU is also known as a Zero Insertion Force socket. That means that it should take absolutely no physical pressure to mount the CPU in its socket, if it's aligned properly. If you find yourself pushing down on your CPU during mobo mounting, you're likely doing great damage to it. So don't!

Intel, the Processor Giant

Intel is the largest semiconductor manufacturer on the planet, and as such, it's had a hand in developing a majority of the technologies powering modern PCs. The company has been the major force behind PCI, AGP, PC100, AC97, USB, and PCI Express. That said, Intel's biggest claim to fame has been the Pentium processor and its heirs. The Pentium 4 is currently the company's flagship CPU. Although you can still buy Pentium IIIs, they've long been banished from desktop systems in retail channels. Indeed, if you want to save money on your dream machine, don't get stingy by buying a PIII. There are far better places to shave off a few dollars and cents. Here's a quick look at your Maximum PC-endorsed, Intel-based CPU options.

  • Pentium 4: There are currently several different versions of Intel's flagchip on the market. First, there's the P4A, a.k.a. the original "Northwood" Pentium 4 with 512KB of cache. It runs on a 400MHz memory bus and uses a 0.13-micron core. Second, we have the P4B. It's also a Northwood, but runs on a 533MHz bus. Third and fourth, there's the P4C, which uses an 800MHz bus, and the Prescott P4E, which uses both 533MHz and 800MHz buses.

  • Figure 3.4Figure 3.4 The Celeron CPU is a basic Pentium 4 core, but the performance is severely limited by its tiny 128KB L2 cache.

    The P4 architecture has a lot of frequency headroom left in it; we expect it to reach 5GHz and beyond! The P4 is also unique in its support for Hyper-Threading, which essentially splits a single physical CPU into two virtual CPUs. So while one application is running floating-point operations, another can use other CPU resources that aren't being tapped. It's a boon to people who run multiple applications simultaneously. Hyper-Threading is available on most P4 processors running at 2.8GHz and faster.

    The standard Pentium 4 Northwood is a great general-purpose CPU. It's very fast for all apps, and can really crank out the floating-point calculations that are crucial for gaming, digital audio, and digital video. That said, once the Prescott-based CPUs exceed 3.6GHz, we expect them to replace the Northwood-based CPUs as Intel's "everyman" processors. However, if you have "more specialized" processor requirements, there are several other Intel CPUs worth considering. Read on...

    Kick-Ass Construction Tip

    Always use some sort of heat-conductive agent between your CPU and heatsink. Without it, air trapped in the gaps of your imperceptibly irregular heatsink surface will hamper your cooler's ability to dissipate processor heat. Thermal paste or a thermal pad will fill those gaps, and allow the heatsink to draw away heat from the CPU more efficiently.

  • Pentium 4: Extreme Edition: In late 2003, Intel unleashed the high-end, limited-run Pentium 4: Extreme Edition processor. For an ultra-premium $1,000 price tag, the Extreme Edition pairs a 3.2GHz Pentium 4 Northwood core with a humongous full-speed 2MB L2 cache. It all adds up to beaucoup gaming performance. In reality, the Extreme Edition has more in common with the even more expensive Xeon processor (see the following bullet). In fact, the only Xeon feature the Extreme Edition lacks is multi-processor support. So, if you want to run dual procs in an Intel rig, you've gotta go Xeon.

  • Xeon: Rest assured, you will pay dearly for dual-processor privileges. Although based on the vanilla P4, the Xeon adds a host of features designed for high-end servers that make these procs enormously expensive. Indeed, an extra 1.5MB of L2 cache does not come cheap. Unless you're building a content-creation rig, you really don't need to be running two processors in tandem, so if you want the performance benefits of a 2MB L2 cache, get a P4 Extreme Edition.

  • Celeron: Intel's current Celeron version is a Pentium 4-based processor that boasts just 128KB of L2 cache and is confined to a 400MHz bus. The current Cellies even operate in most motherboards designed for 400MHz-bus and 533MHz-bus P4s. The Celeron offers more than enough torque for granny to browse the Net, but gamers and other power users would be better served by purchasing a slower Pentium 4 than a faster Celeron.

Kick-Ass Construction Tip

CPUs sold as "white-box" or "OEM" versions seem like a great deal at first glance. They're usually cheaper than retail processors of the same speed, but they can present problems. First, OEM processors usually have a very short warranty—frequently less than 30 days. Second, they normally don't come with bundled coolers (a standard feature in retail bundles), so the money you save vanishes when you have to spend $30 on a heatsink.

AMD, the Feisty Upstart

In the five years since the introduction of AMD's Athlon line of processors, the Athlon has consistently given the Pentium III and Pentium 4 a run for their money. The ultimate humiliation came when AMD beat Intel to the 1GHz mark. Now, after years of eating dust, AMD has tasted the sweet nectar of victory and has no intention of giving up. The company's Athlon 64/FX CPU is currently its flagship consumer CPU, which was the PC world's first desktop CPU to include support for 64-bit apps and operating systems. As you read this book, older 32-bit Athlon XP processors might still be available, but they are definitely dinosaurs. Here's a look at AMD's current consumer-level offerings.

  • Athlon FX: The latest 64-bit processors from AMD—dubbed Athlon FX—give smokin' fast performance in today's games and demanding content-creation apps. The FX series absolutely blows away the standard Pentium 4 in most memory-bandwidth dependent tests (read: almost all benchmarks). The Athlon FX core runs at a much lower clock speed than the P4, but the chip benefits greatly from an integrated 128-bit memory controller.

  • Yes, the Athlon FX is quite a performer, but it doesn't offer very inviting upgrading options. You see, instead of making its memory controller part of the motherboard chipset (the traditional approach Intel still uses), AMD integrated the memory controller Athlon FX into the CPU itself. This integration enables the memory controller to provide a lightning-fast connection between the CPU and system memory, but it also limits the CPU to using a single type of memory. To wit: When we went to press, the memory controllers integrated into the Athlon FX-51 and FX-53 CPUs only supported DDR400 memory. So, when faster DDR-II memory comes out later this year, FX-51 and FX-53 owners will need to buy new CPUs if they want to upgrade to faster motherboards and faster memory.

    Figure 3.5Figure 3.5 This Alpha cooler's unique design allows you to mount whatever fan you want to the cooler. If you plan on overclocking, you can connect a small, high-speed fan. If you're more concerned with minimizing noise, you can use a larger, low-speed fan.

    That's quite a gotcha, and you've been warned. Nonetheless, the Athlon FX series of processors performs nearly as fast as the Pentium 4 Extreme Edition, and at a fraction of the cost. We recommend the Athlon FX for any PC builder looking for top-class performance at a reasonable price. Just be prepared to give your Athlon FX machine away to your nephew by the time Doom 4 or 5 rolls around.

    Chipset Compatibility Chart

    Each CPU is only compatible with certain specific chipsets. Here's the list of all Pentium 4, Athlon FX, and Athlon XP chipsets available now, and the system bus speeds they support:


    Processor Type

    Fastest Memory Supported

    Intel 875P

    Pentium 4, Celeron

    DDR400 Dual-Channel

    Intel 865G

    Pentium 4, Celeron

    DDR400 Dual-Channel

    Intel 865PE

    Pentium 4, Celeron

    DDR400 Dual-Channel

    Intel 865P

    Pentium 4, Celeron

    DDR333 Dual-Channel

    Intel 850E

    Pentium 4, Celeron

    PC1066 RAMBUS Dual-Channel

    Via PT880

    Pentium 4, Celeron

    DDR400 Dual-Channel

    Via PT800

    Pentium 4, Celeron

    DDR400 Single-Channel

    Via K8T880 Pro

    Athlon 64, Athlon FX

    (Determined by CPU)

    Via K8T800 Pro

    Athlon 64, Athlon FX

    (Determined by CPU)

    Via KT880

    Athlon XP

    DDR400 Single-Channel

    Via KT600

    Athlon XP

    DDR400 Single-Channel


    Athlon 64, Athlon FX

    -(Determined by CPU) nForce3 250


    Athlon 64, Athlon FX

    -(Determined by CPU) nForce3 150

    nVidia nForce2

    Athlon XP

    DDR400 Dual-Channel

  • Athlon 64: AMD's first consumer-level, 64-bit CPU for Windows-based PCs is the Athlon 64. (Yes, it's true that Apple was the first company to rush a 64-bit PC proc out with the G5 series, but we're not talking about building Macs, Billy.) Based on the same "Hammer" core as the Opteron processor, the Athlon 64 has one key feature that differentiates it from its FX brother: It's handcuffed by a single-channel memory controller. That's right: The plain-vanilla Athlon 64 only supports a 64-bit memory controller, whereas the FX series has a dual-channel 128-bit controller that can move twice as much data with the same speed memory. The Athlon 64's performance suffers because of this memory bandwidth deficiency, making it a poor choice for demanding power users.

  • Athlon XP: The Athlon XP remains a budget PC builder's favorite. Its 32-bit core still performs extremely well, even with demanding applications and games. The fastest version in the Athlon XP lineage clocks in at 2.2GHz, uses a 0.13-micron process, packs in 512KB of L2 cache, and runs on a 400MHz bus. It was designed to be a screamer in floating-point software (games and digital media apps) and actually outperforms the Pentium 4 when both chips are running at the same clock frequency. And herein lies the problem: The Athlon XP simply can't reach the high clock frequencies achieved by the P4. Still, the Athlon XP's floating-point performance makes it ideally suited for older mathematic and scientific applications that have not been optimized for the Pentium 4.

  • Before you buy an Athlon XP, you need to know about AMD's goofy performance-rating scheme. Instead of just tagging their XPs with a clock-speed rating, the CPUs are assigned a rather arbitrary name based on relative Pentium 4 performance. Thus, a 2.167GHz Athlon XP running on a 333MHz bus is marketed as an "Athlon XP 3000+." What does the 3000+ mean? AMD swears on a stack of Maximum PCs that it's not a tip-off that the CPU runs as fast a 3GHz P4, but we don't buy it. It's just a little too convenient that the performance numbers perfectly line up with Intel's clock speeds.

    Figure 3.6Figure 3.6 Oddly enough, the Zalman CNPS6500 Series of coolers is very effective at quietly cooling both Athlon and Pentium 4 processors. If you choose to use a nonstandard shaped cooler, make sure it will fit in your PC.

    For regular-old consumers, the numbering scheme actually makes sense, as the average Joe and Jane don't have the time (or technical savvy) to understand that a 2.2GHz CPU can run as fast as a 2.8GHz CPU in many applications. For hobbyists, however, the performance rating scheme presents a confusing mess. For example, AMD has two 3000+ CPUs—the original one clocked at 2.167GHz and running on a 333MHz bus, and a newer version clocked at 2.1GHz on a 400MHz bus. AMD's variables (clock speed, bus speed, and cache size) are many, and lead to confusion. For example, it's usually better to sacrifice a few megahertz for a larger L2 cache and a 400MHz bus speed, but there's no way to know exactly what you're getting by looking at a silly performance rating.

    That said, as long as you do a little extra research when buying an Athlon XP, you'll be OK. In fact, most stores and websites are very clear about labeling the attributes of specific Athlon XPs so you don't get mixed up.

    Ask the CPU Doctor

    Q: My machine randomly reboots after several hours of playing games or watching movies—what could it be?

    A: A likely culprit when you have spontaneous reboots is an overheated CPU. If you suspect that your CPU is running too hot, you can usually monitor the CPU temperature using a special utility that comes with your motherboard. If your CPU is running much above 40° Celsius, you should consider replacing your CPU cooler to get more air moving over the core.

  • Athlon MP: Take an Athlon XP, test it for compatibility in a dual-processor configuration, confirm that it passes, and then label it "Athlon MP." That's pretty much the Athlon MP story. It's just an XP chip that's multi-processor-ready. The Athlon MP was supposed to be AMD's big push into the server-scale arena, but it has been hindered by a lack of chipset support. The 760MPX is still the only chipset ordained for Athlon MP support, but it runs a puny 266MHz memory bus and wimpy DDR266 memory. In fact, poor chipset support and the kick-ass performance of newer AMD Opteron chips have doomed the Athlon MP to the scrap heap. So don't buy one of these stinkers, no matter what!

  • Opteron: AMD's 64-bit server and workstation processor is called Opteron. Like the Athlon FX and Athlon 64 processors, the Opteron breaks from tradition by embedding a dual-channel memory controller directly into the CPU die. Its large, integrated L2 cache helps the Opteron shine in high-intensity server apps, but its lower clock speed really hurts performance in consumer apps, such as games and video-encoding software. Because the Opteron isn't intended for desktop use, we recommend it only for people looking to build high-powered servers and workstations.

  • Duron: The Duron is AMD's version of Intel's Celeron. A budget chip built from a derivative of the Athlon XP, the Duron has only 64KB of L2 cache and is limited to a 200MHz system bus. In the early days of the Athlon XP, the Duron could outperform a low-end Celeron, but today it's solidly outclassed by Intel's current-generation Celeron. AMD shelved the Duron earlier this year, and has pushed the Athlon XP into the low-end market to compete with the Celeron. The price on an old, dust-gathering Duron processor might be right, but the performance sure isn't.

The Good, Bad, and the Ugly of CPU Cooler Design

Words of Wisdom: You're only as cool as your CPU cooler!

Figure 3.7Figure 3.7

The copper core on this Thermaltake cooler helps the heatsink pull heat away from the CPU and into the rest of the system. Some coolers are made entirely of copper, but we prefer that the copper core in a heatsink be made of another material. Because copper is very soft, it's easy to damage all-copper heatsinks.

Figure 3.8Figure 3.8

The type of spring clip on this Athlon XP cooler requires a frightening amount of force to latch onto the CPU socket. If you're building an Athlon XP, be especially careful when you attach the heatsink to the CPU socket, as it's very easy to crush the unprotected CPU core and render your CPU unworkable.

Figure 3.9Figure 3.9

This Alpha cooler looks swanky, but it's very difficult to mount on your CPU socket. Instead of a standard mounting bracket, you have to physically screw it into a bracket that attaches to your mobo. This is definitely a heatsink to avoid if you plan on frequently upgrading your CPU.

Figure 3.10Figure 3.10

By using a large, slow fan on this Thermaltake Athlon 64 cooler, this heatsink can keep hot CPUs cool, without making a whole lot of noise. Look for a CPU heatsink with a large slow-moving fan instead of a smaller fast fan.

Figure 3.11Figure 3.11 Anatomy of the Prescott Pentium 4

What'll It Be, Bub? Intel or AMD?

Intel or AMD? It can be a tough choice. But it's not all about cache sizes, transistor counts, and which one has the better commercials. The perfect CPU for you will greatly depend on what you intend to do with it.

If you're interested in playing games, the Pentium 4 Extreme Edition is the leader for now, but the Athlon FX-53 is nipping right at its heels. And once you factor in that Athlon FX chips cost significantly less than the hard-to-find Extreme Editions, you have compelling arguments for each platform. Don't discount the standard Pentium 4, either. It delivers strong performance and value, and shouldn't be overlooked.

If gaming isn't your top priority, there are other factors that should influence your choice. If you intend to handle a lot of media-intense chores such as MP3 encoding and DV editing, or if you're interested in 3D rendering apps (such as Lightwave 3D or 3ds max, which have been specifically coded for Intel instructions), then the P4 is the way to go.

We don't recommend investing your hard-earned cash in Pentium III, Duron, Celeron, or Athlon MP chips, as these are all dead-ends, upgrading-wise. Xeons and Opterons are too expensive when purchased in pairs for the vast majority of consumers, and there's a good argument that says first-time PC builders should not be playing around with dual-processor projects.

Keeping Your CPU Cool

At this point, you should have a pretty good idea of which CPU type to purchase, so it's time to give some attention to CPU cooling. Every modern processor needs a good amount of cooling to dissipate the heat generated by today's power-hungry transistors. The vast array of CPU cooling devices you can buy today even intimidates Maximum PC editors, but we'll let you in on a little secret: Most people—even enthusiast PC builders—can safely stick with the stock cooler that comes bundled in retail CPU packaging. Both Intel and AMD spend millions of dollars developing custom-tailored fan/heatsink combos that are quieter and more effective than many aftermarket coolers.

Now, there are indeed reasons to upgrade from stock cooling. Running your CPU at a higher-than-rated clock speed—also known as overclocking—generates more heat than most stock fans are designed to dissipate. So overclockers definitely need more powerful coolers. Also, if you're building a PC for your living room, you might want to consider a quieter solution. By combining larger, slower-moving fans and larger-than-normal heatsinks, some aftermarket coolers designed for low noise output can pull heat away from a CPU every bit as effectively as Intel and AMD coolers.

Another good way to minimize noise is to consider installing a fanbus. Not to be confused with the short bus, you can use a fanbus to control the speed at which your fans turn. Fanbuses usually fit into a spare 5.25-inch drive bay, and are then connected to all the fans in your system. Once you've connected all your fans, you can use the controls built into the fanbus to adjust fan speeds as necessary. When you're working in Word, you can crank the speed down, but when you're fragging online, you can ratchet up the fan speed to keep your components cool.

Figure 3.12Figure 3.12 This Innovatek water-cooling rig will keep your PC cool, and it's virtually silent to boot.

Fancier fanbuses even include temperature sensors that you can place near the area that a controlled fan keeps cool. When the temperature rises, the fanbus turns the fan speed up automatically. When everything is cool again, the fanbus slows the fan back down to its quiet mode.If you're truly fanatical about noise reduction and/or overclocking, consider water-cooling kits. Most water-cooling rigs use nearly silent aquarium pumps to move a constant stream of chilly water through a cooling block that attaches directly to your hot CPU. Just be warned that water-cooling is not for everyone. In addition to the danger of a system-destroying leak, water-cooled systems require much more maintenance than air-cooled PCs. You have to maintain water levels and keep a constant eye peeled for leaks.

Does your case sport a window? If it does, you should definitely consider upgrading your CPU heatsink to one that brings a little more bling! After all, what's the point of having a fancy case window if you just have plain vanilla parts inside? There are lots of Pentium 4, Athlon XP, and Athlon FX heatsinks that light up, just plain look cool, or both.

Regardless of your reasons, when purchasing a third-party CPU heatsink, make sure it's rated for your CPU. That means it can dissipate as much heat as that CPU will generate at stock clock speeds, and includes the special mounting brackets required to attach to your CPU's socket.

CPU Spec Speak

Cache Size

Your CPU's cache—also called L2 cache—is high-speed RAM, built directly onto the CPU core. As a general rule, the more cache your processor has, the faster it will run hardcore applications and games. Don't settle for a CPU with less than 512KB of L2 cache.

Bus Speed

The speed at which the CPU communicates with system memory, typically measured in megahertz. Because the CPU multiplier in most processors is locked, increasing bus speed is the only way most people can overclock their systems.

CPU Multiplier

An integer that determines a CPU's core clock speed. Modern CPUs will only run when the motherboard is set at a factory-specified clock multiplier. The system simply won't boot if the clock multiplier is set to a unauthorized value in the BIOS. You can calculate your CPU's multiplier by dividing the CPU's rated core speed by the bus speed. For example, early 400MHz processors ran a 100MHz system bus on a 4x multiplier.

Memory Controller

A specialized section of the motherboard's chipset (or in the case of the Athlon 64 family, the CPU itself) designed to direct memory traffic and support specific memory types. Usually the memory controller is located in the motherboard's northbridge chip, allowing motherboard manufacturers to pop new northbridge chips on their boards whenever a new memory standard hits the market.

Core Speed

The speed of the CPU, usually measured in either megahertz or gigahertz.

Floating-Point Number

A number bearing decimal points, such as 9.89. CPUs have more difficultly crunching floating-point numbers than integer numbers (whole numbers). Floating-point calculations offer a higher level of precision, and are integral to 3D games.

Branch Prediction

The capability of a CPU to predict conditional branches. The sophistication of this feature varies greatly, from static prediction (always guessing a branch will fork in the same direction) to dynamic prediction (basing a prediction on previous behavior). When you click an OK button in an interface menu, you are effectively fulfilling a branching prophecy! (It's a gross simplification, Timmy, but we're trying to keep things easy.)

Ask the CPU Doctor

Q: The heatsink that came with my processor has a small pad made of a putty-like substance stuck where the CPU will touch it. What is it?

A: That putty-like substance is a thermal pad. It serves the same basic function as thermal paste, but it's much easier to work with. If your thermal pad is scratched, or part of it is missing, you should consider scraping it off with a straight razor and then using thermal paste instead. The first time you fire up your system after the heatsink is affixed, the thermal pad will heat up and melt, forming a bond using the perfect amount of material between the CPU and the heatsink.

Dream Machine 2004 Contender

Here's a close-up look at the odds-on favorite CPU and CPU cooler for next year's Dream Machine

AMD Athlon FX-53

What's the secret sauce in the Athlon FX? The on-chip memory controller gives the CPU ready access to your system RAM, letting it squeeze every ounce of performance from your high-speed memory. The FX CPU—and the other Athlon 64-based processors, for that matter—are also extremely good at floating-point math. Games and CPU-heavy multimedia apps, such as video and audio encoders and decoders, are notorious users of floating-point math.

The extremely efficient use of memory bandwidth and lightning-fast floating-point performance make the Athlon FX-53 a strong contender for Dream Machine 2004. In fact, the Athlon FX-53 is the fastest CPU we've tested for games, and damn near anything else for that matter. The FX-53 even smokes the more expensive Pentium 4 Extreme Edition in all but a few benchmarks.

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