CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [78]
Figure 5-46 Pentium 4 (478-and 423-pin)
Intel switched to the Land Grid Array (LGA) 775 package with the release of a Pentium 4 CPU codenamed Prescott (Figure 5-47). Again, even though the LGA 775 package has more pins than a Socket 478 package, it is smaller. With the Pentium 4 CPUs codenamed Northwood and Prescott, Intel unveiled an interesting advancement in superscalar architecture called hyperthreading.
Figure 5-47 Pentium 4 LGA
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NOTE P4 Prescotts and Northwoods came in hyperthreaded and nonhyperthreaded versions.
With hyperthreading, each individual pipeline can run more than one thread at a time—a tricky act to achieve. A single Intel P4 with hyperthreading looks like two CPUs to the operating system. Figure 5-48 shows the Task Manager in Windows XP on a system running a hyperthreaded Pentium 4. Note how the CPU box is broken into two groups—Windows thinks this one CPU is two CPUs.
Hyperthreading enhances a CPU’s efficiency but with a couple of limitations. First, the operating system and the application have to be designed to take advantage of the feature. Second, although the CPU simulates the actions of a second processor, it doesn’t double the processing power because the main execution resources are not duplicated.
Starting with the LGA 775 Prescotts, Intel dumped the convention of naming CPUs by their clock speed and adopted a cryptic three-digit model-numbering system. All Prescott Pentium 4s received a three-digit number starting with a 5 or a 6. One of the 2.8-GHz Pentium 4 CPUs is a 521, for example, and one of the 3-GHz processors is called the 630.
A late version of the Pentium 4 CPU was released, called the Pentium 4 Extreme Edition. The Extreme Edition CPUs incorporated a large L3 cache and other architectural details borrowed from Intel’s Xeon line of server CPUs. The Pentium 4 Extreme Edition also had some of the highest wattages ever recorded on any Intel desktop CPU—over 110 watts! Extreme Edition CPUs ran incredibly fast, but their high price kept them from making any significant impact on the market.
Figure 5-48 Windows Task Manager with the Performance tab displayed for a system running a hyperthreaded Pentium 4
These Pentiums reached the apex of clock speeds, approaching 4 GHz. After this, Intel (and AMD) stopped the CPU clock-speed race and instead began to concentrate on parallel and 64-bit processing (both to be discussed later in this chapter).
Mobile Processors
The inside of a laptop PC is a cramped, hot environment where no self-respecting CPU should ever need to operate. Since the mid-1980s, CPU manufacturers have endeavored to make specialized versions of their processors to function in the rugged world of laptops. Over the years, a number of CPU laptop solutions have appeared. Virtually every CPU made by Intel or AMD has come in a mobile version. You can usually tell a mobile version by the word “mobile” or the letter “M” in its name. Here are a few examples:
Deciphering the Numbers
Give it up. Intel must have some scheme for their CPU numbering, but it doesn’t match the processor speed. They call a 2.66-GHz CPU a 506, for example, which might lead you to believe that the “6” reflects the “66” in the speed. But the 2.8-GHz CPU that followed was named the 511. Go figure!
Here’s what Intel says on www.intel.com/products/processor_number/: “Intel processor numbers are based on a variety of features that may include the processor’s underlying architecture, cache, Front Side Bus, clock speed, power and other Intel technologies. A processor number represents a broad set of features that can influence overall computing experience, but is not a measurement of performance.”
Mobile Intel Pentium III
Intel Pentium M
Mobile AMD Athlon 64
AMD