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Hardware Emergency Room:   CPU
Contents: The CPU
Upgrading Your CPU
CPU Problems
Over clocking

CPU - Central Processing Unit
Your computer's CPU (or processor) is centrally located on its motherboard, and it is the brain of your PC.  The CPU carries out much of the work on your system, and is constantly passing data and receiving instructions.  There are many brand names and many manufacturers of CPUs, and the manufacturers are often producing several models at once, which overlap.  This can make for a difficult time in identifying your computer's particular CPU.  Special Utility Diagnostics programs can tell you the family, model, and mask of your CPU.

CPU
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CPUs are usually specified by two main parameters:
  • Speed: cycles per second counted in megahertz (MHz).
  • Width: I/O bus, internal registers and memory address bus.
For example, a Pentium II 333MHz has a  64-bit I/O bus width, a 32-bit internal register size, and a 36-bit memory address bus width.  An older 486 DX4 had a CPU speed of 100 MHz, and 32-bit I/O bus, internal register and memory address bus widths.
These specifications, along with the manufacturer and model are what uniquely identifies a given CPU.
All of today's CPUs share a common need for cooling.  The cooling mechanisms (usually a fan and a heat sink) are matched to the CPU size, and must be attached properly to provide maximum cooling.  Most modern systems have an improved motherboard design that provides for superior cooling of the CPU because of its position near the power supply.

CPU Fan
cpu
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Modern systems have a Socket or Slot Number that facilitates interchangeability of CPUs.  These numbers (Socket 1, Socket 2, Socket 3 and so forth) are directly related to the processor chips that they can support.  Pentium II processors and beyond use a slot where the processor card or cartridge is installed (Slot 1 or Slot 2).

Upgrading Your CPU

One very common way of improving your system is to upgrade its CPU, thereby increasing clock frequency, cache and other attributes that have a direct impact on your computer's performance.

CPU upgrades are a relatively easy and common system improvement.  Upgrading the processor is often the fastest and easiest way to gain performance without upgrading the entire motherboard.  To maximize your motherboard you can almost always upgrade to the fastest CPU that its processor socket will support.  Some upgrades will require a voltage regulator adapter.  For example, if your motherboard has a Pentium Socket 5 with a 100MHz CPU, you can upgrade to a Pentium MMX 233MHz, as long as you add in a 2.8v adapter.
You need to stay within the same class when upgrading your CPU.  You can replace a slow 486 with a faster one, even possibly from a different vendor, but you can not replace it with a Pentium without replacing your entire motherboard or purchasing a special version of the new processor designed specifically for this type of upgrade.
Be very careful when you replace your new CPU that you install it properly aligned.   If you accidentally put it in sideways it is likely you will ruin your new CPU and your motherboard -- an expensive mistake.  From that point on your motherboard may ruin any chip you install.

CPU
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Don't forget that you should buy a new fan when you upgrade your CPU.  Better yet, get a boxed CPU with an integrated fan.  That way you'll know you are getting the proper size of fan.  Make sure your fan has a ball-bearing motor; the cheaper sleeve bearing motors often freeze after a very short life.  If you've max-ed out on your CPU then your next step is a motherboard upgrade.

CPU Fan
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CPU Problems

When a CPU fails, it generally fails in a big way.  A System that has not been changed recently, but suddenly does not boot, or freezes during the boot process, is a good candidate for a CPU problem. 

CPU
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If your computer powers up briefly, and perhaps even your hard drive spins up, but then your system dies suddenly and completely, you may have a problem with your CPU:
  • Make sure that the CPU is installed securely in its socket or slot.  Make sure all system cables and connectors are secure.
  • Check first for hardware conflicts or a defective peripheral device by removing all such peripherals and expansion boards and attempting to start the system.  If it starts, one of the expansion devices is interrupting your system's operation.  Re-install each device, one at a time, and check the system, to determine which device is bad.
  • Replace your CPU with a known, good, CPU in the motherboard.  If it works, it is probable that your CPU is bad, if it does not, you may have to replace your motherboard.

CPU Socket
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If your system starts up without a problem but then crashes or freezes a few minutes after operation your CPU may be over-heating:
  • Make sure that the CPU is installed securely in its socket or slot.  Make sure all cables and connectors are secure.
  • Make sure your CPU heat-sink/fan is working properly.  If you do not have a fan, consider adding one.

CPU Fan
cpu
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If your system starts up without a problem but crashes or freezes when a certain application is run:
  • Try a known, good CPU in the motherboard.
If you receive a beep code that indicates possible CPU fault:
  • Check that the motherboard's power connector is securely inserted.
  • Try a known, good CPU in the motherboard.  If the new CPU fails to correct the problem, you may have to replace the motherboard.

Power Cable
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If your system runs fine but your BIOS reports the wrong type of CPU:
  • The motherboard BIOS is not written to support your particular CPU directly.
  • You may need a BIOS upgrade, if available.  Contact your system or motherboard manufacturer.

Over clocking

Over clocking is when a CPU is run at a speed higher than it is rated for.  The concept was not invented by high-tech users trying to get the most from their hardware, but by unscrupulous vendors who, to save money, would install a CPU rated for less than the actual operating speed. 

If you suspect that your vendor may have done this, you can look at your chip's markings.  Usually the part number will end in a suffix of -xxx where xxx is the number indicating the maximum speed.  For example -333 indicates that the chip was rated for 333MHz operation.  One word of caution -- some vendors actually remarked the CPUs, obscuring the original part number.
Among the devotees, over clocking has become more of a religion than a science.   You can set jumpers on your motherboard to force your CPU to run faster than it is designed to run.  It is easy to be dazzled by the concept because the CPU is one of the most expensive components on the motherboard, and faster-rated chips cost more money.   In addition, it is widely speculated that the manufacturers rate their chips conservatively.
Despite this,  we do not recommend over clocking here as the chip will run hotter than it would normally.  Symptoms of overheating include random lockups, glitches and headaches.  If you do decide to try to over clock your CPU and experience such problems, it would be wise to return it to the original speed.
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Disclaimer:  These pages are provided for information purposes only.  We cannot be held responsible for any damage you might inflict on your system while using the information contained herein.  We recommend you always refer any technical matter that is "over your head" to a qualified computer technician.
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2011 Double-Hammer Computer Services.  All rights reserved.
Last Updated: September 04, 2011

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