Central Processing Unit (CPU) Tutorial |
The Central Processing Unit (Normally called a processor or CPU) is the brain of the PC. It executes instructions, allowing a computer to perform all kinds of tasks. From burning CDs or DVDs to something as simple as a mouse click, the CPU is always at work. Processors consist of two parts: The Arithmetic Unit, which performs math and logical operations, & the Control Unit, which decodes instructions. Over the years, processors have become extremely fast. AMD and Intel are the two primary manufacturers.
CPU technology constantly changes, probably faster than any other type of hardware. On this page I highlight what I consider are the main specifications.
When looking at a CPU, you don't really see the processor itself. The little piece of silicon that contains the circuitry is very small. What you actually see is the package that it's in. Both AMD and Intel have had many types over the years. Packages are usually square with pins underneath that fit into holes on the CPU's slot. This arrangement is known as Pin Grid Array (PGA) and is now only used by AMD.
Intel abandoned PGA years ago and now have the pins located on the slots themselves, called Land Grid Array (LGA).
Types
Processors are designed to fit into a certain type of socket on the motherboard. Every socket has a name, indicating whether it's for an AMD or Intel CPU. Keep in mind that AMD and Intel have different socket designs, so their processors are not interchangeable. But regardless of manufacturer, CPUs usually differ in the number of pins used and are often named accordingly.
| Socket Type | Manufacturer |
| LGA 771 (Socket J) | Intel (Xeon Server) |
| LGA 775 (Socket T) | Intel |
| LGA 1156 (Socket H) | Intel |
| LGA 1166 (Socket B) | Intel |
| AM2 | AMD |
| AM2+ | AMD |
| AM3 | AMD |
AM2+ and AM3 mainly differ in terms of the memory each supports. AM2+ supports DDR2 while AM3 supports DDR2 and DDR3, making it backward-compatible with the AM2+ motherboard.
Rates & Data Transfer:
What characterizes a computer processor is its speed or rate - how fast it can execute instructions. As of now, speed is measured in gigahertz (GHz), or billions of cycles a second. Some CPU rates are 2.0 GHz, 2.40 GHz, and 3.20 GHz. These rates and others are obtained by using the motherboard's bus speed.
CPUs contain a multiplier that when multiplied by the bus speed, yields the appropriate CPU speed for a given motherboard. For example, if the speed of a motherboard is 800 MHz, and the CPU multiplier is 4, then the processor's speed is 800 x 4 = 3200 MHz or 3.2 GHz.
Because the CPU greatly determines the overall performance of a PC, the type of processor and its speed are two of the main factors to look for when deciding to buy a computer. But keep in mind there are other important things, such as the amount of memory.
CPUs are either 32-bit or 64-bit. This means how much data that can be processed in terms of bits. In computers data is composed of 1's and 0's (e.g. 01110010). Each individual 1 or 0 is called a bit. A 32-bit CPU can process a max of 2^32 (2 raised to 32nd power) or about 4.3 billion bits per cycle. A 64-bit processor 2^64 or about 18,400,000,000,000,000,000 of data per cycle. The more data a computer can handle means improved performance.
The amount of memory supported by a processor is also determined by the number of bits. Using the same math above, a 32-bit processor supports 2^32 or approximataely 4 GB of memory.
Cache:
In addition to CPU speed, another important processor feature that influences performance is the amount of cache (pronounced cash) it has. CPU cache is memory set aside for the most frequently used data. There's Level 1, Level 2, and Level 3 (commonly just called L1, L2, and L3). L1 uses extremely fast and expensive SRAM (Static RAM) and is the smallest in size. L2 is slightly larger in size. Both L1 and L2 are located on the processor. L3 is the largest and is usually located outside the CPU and shared by all the cores. When data is requested, the CPU first checks the L1 to see if it's there. If not it checks L2 and so on. Accessing data in the cache is far more faster and efficient than fetching it from RAM.
Dual Core & Multicore Processors:
Most computer processors today are dual core or multicore. Both terms are generic for any processor that literally contains two or more CPUs in one package. Both Intel and AMD produce versions of these processors. AMD's Athlon x2, Turion x2, and Intel's Core 2 Duo and Core 2 Extreme are examples of dual core CPUs. Multicore examples are the AMD Phenom x3 and x4 and Intel's Core 2 Quad and the Core i7. These powerful CPUs allow users to run several applications simultaneously as well as play the latest games.
HyperTransport:
AMD's HyperTransport Technology has been around since 2003. All of their processors based on AMD64 architecture use HypertTransport. It eliminated the front side bus (FSB) and took the memory controller, which was previously on the chipset, and placed it on the processor. The old front side bus used one data path from the CPU for memory and I/O (Input/Output). HTT implements two separate data paths for memory and I/O. Also, unlike the FSB, data flow between the CPU and the chipset can be sent and received at the same time.
In late 2008, Intel released the quad-core Core i7 CPU with its own version of HyperTransport called QuickPath Interconnect (QPI). It basically does the same thing as HTT but only uses DDR3 memory, and depending on which model some support three memory channels. They also had to develop a new chipset which includes PCI Express enhancements.
In addition supporting QPI, the Core i7 includes 64K L1 and 256K L2 cache for each core, 8MB L3 shared cache, turbo boost, and HD boost for improved high definition. It brings back the old hyper-threading. Before dual cores came on the scene, hype-rthreading was used to make the operating system think there were two processors. Since the i7 is quad-core hyper-threading makes it seem as if there are eight cores.
All these combined make for an extremely fast system for multitasking, gaming and multimedia needs.
The Core i7 computer processor comes in several variations, and it can get confusing. There is also the Core i5 and Core i3. Below are tables showing the Intel processors recently released in each class.
| i7 Series Processor (All Quad Core & Use Hyperthreading) | Released | Speed | Transfers/Sec | Maximum Amount of Memory & Number of Channels Supported | Integrated HD Graphics | Cache Size |
| i7-930 | Q1 2010 | 2.8 GHZ; 3.46 GHz w/Turbo Boost | 4.8 GT/s | 24 GB, 3 Channels | N | 8 MB |
| i7-960 | Q4 2009 | 3.2 GHz; 3.46 GHz w/Turbo Boost | 4.8 GT/s | 24 GB, 3 Channels | N | 8 MB |
| i7-860 | Q3 2009 | 2.8 GHz; 3.46 GHz w/Turbo Boost | 2.5 GT/s | 16 GB, 2 Channels | N | 8 MB |
| i7-870 | Q3 2009 | 2.93GHz; 3.6 GHz w/Turbo Boost | 2.5 GT/s | 16 GB, 2 Channels | N | 8 MB |
| i7-950 | Q2 2009 | 3.06 GHz; 3.33 GHz w/ Turbo Boost | 4.8 GT/s | 24 GB, 3 Channels | N | 8 MB |
| i7-920 | Q4 2008 | 2.66 GHz; 2.93 GHz w/Turbo Boost | 4.8 GT/s | 24 GB, 3 Channels | N | 8 MB |
| i7-940 | Q4 2008 | 2.93 GHz; 3.2 GHz w/Turbo Boost | 4.8 GT/s | 24 GB, 3 Channels | N | 8 MB |
| i7 Extreme Editions | Released | Speed | Transfers/Sec | Maximum Amount of Memory & Number of Channels Supported | Integrated HD Graphics | Cache Size |
| i7-980X ( 6 Cores) | Q1 2010 | 3.33 GHz; 3.6 GHz w/Turbo Boost | 6.4 GT/s | 24 GB, 3 Channels | N | 12 MB |
| i7-975 (4 Cores) | Q2 2009 | 3.33 GHz; 3.6 GHz w/Turbo Boost | 6.4 GT/s | 24 GB, 3 channels | N | 8 MB |
| i7-965 (4 Cores) | Q4 2008 | 3.2 GHz; 3.46 GHz w/ Turbo Boost | 6.4 GT/s | 24 GB, 3 channels | N | 8 MB |
| Processor | Released | Speed | Transfers/Sec | Maximum Amount of Memory & Number of Channels Supported | Integrated HD Graphics | Cache Size |
| i3-530(Dual Core) | Q1 2010 | 2.93 GHz | 2.5 GT/s | 16 GB, 2 Channels | Y | 4 MB |
| i3-540(Dual Core) | Q1 2010 | 3.06 GHz | 2.5 GT/s | 16 GB, 2 Channels | Y | 4 MB |
| i5-670(Dual Core) | Q1 2010 | 3.46 GHz; 3.73 GHz w/Turbo Boost | 2.5 GT/s | 16 GB, 2 Channels | Y | 4 MB |
| Mobile Processors | Released | Speed | Transfers/Sec | Maximum Amount of Memory & Number of Channels Supported | Integrated HD Graphics | Cache Size |
| i3-350M(Dual Core) | Q1 2010 | 2.26 GHz (No Turbo Boost) | 2.5 GT/s | 8 GB, 2 Channels | Y | 3 MB |
| i5-540M(Dual Core) | Q1 2010 | 2.53 GHZ; 3.066 GHz w/ Turbo Boost | 2.5 GT/s | 8 GB, 2 Channels | Y | 3 MB |
| i7-640UM(Dual Core) | Q1 2010 | 1.2 GHz; 2.266GHz w/Turbo Boost | 2.5 GT/s | 8 GB, 2 Channels | Y | 4 MB |
| i7-920XM Extreme(Quad Core) | Q3 2009 | 2 GHz; 3.2 GHz w/Turbo Boost | 2.5 GT/s | 8GB, 2 Channels | N | 8 MB |
Believe or not, this is not the full list. To see others you can go to Intel's CPU page. Below are tables showing AMD CPUs specs.
| CPU | Speed | Transfers/Sec | L1 Cache | L2 Cache | Type of Memory Supported |
| Athlon II x3 (Three Core) | 3 GHz | 4.4GT/s | 128 KB | 512 KB | DDR2 & DDR3 |
| Athlon II x4 (Quad Core) | 2.9 GHz | 4.4 GT/s | 128 KB | 512 KB | DDR2 & DDR3 |
| Phenom II x2 (Dual Core) | 3.2 Ghz | 4.0 GT/s | 128 KB | 512 KB | DDR 2 & DDR3 |
| Phenom II x3 (Three Core) | 2.8 GHz | 4.0 GT/s | 128 KB | 512 KB | DDR2 & DDR3 |
| Phenom II x4 (Quad Core) | 3.4 GHz | 4.0 GT/s | 128 KB | 512 KB | DDR2 or DDR3 (Depends on the type of socket) |
| Mobile CPUs | Speed | L1 Cache | L2 Cache | Type of Memory Supported |
| Turion x2 Ultra | Max 2.4 GHz | 2 MB | DDR2 | |
| Turion Neo x2 | 1.6 GHz | 128 KB | 1 MB | DDR 2 |
