How to install socket 5 and socket 7 processors

Entry Notes

Posted: 11252006
Author: Ing. Demir Cutts
Category: Memory Processor Motherboards and buses

Socket 5 and Socket 7 motherboards must be configured properly to support the particular processor you are installing.

  • 1. Use the processor and motherboard documentation to verify that the processor and motherboard are compatible, and to determine the proper settings for bus speed, CPU multiplier, core voltage, and I/O voltage. Use the motherboard manual or manufacturer's web site to locate the configuration jumpers and to determine the jumper settings that match those required by the new processor. On some systems, settings are made by a combination of jumper settings and entries in BIOS setup. There are four settings you may have to make, all of which may not be present on a given motherboard:
    Bus speed

    All Socket 5 and Socket 7 motherboards provide settings at least for 60 and 66 MHz. Some motherboards provide higher bus speeds, often including 75 and 83 MHz. These higher bus speeds are used to overclock a 60 or 66 MHz processor—running it faster than its rated speed. Do not use these settings unless you are sure you want to overclock the processor. More recent Socket 7 motherboards, called Super7 motherboards, also provide 95 and 100 MHz bus settings, which are the standard speeds for newer Socket 7 processors. These motherboards may also include various overclocking settings, including 103, 112, and 124 MHz. Again, avoid using overclocking unless you are making an informed decision to do so.

    CPU multiplier

    The product of the bus speed and CPU multiplier determines how fast the processor runs. For example, using a 60 MHz bus speed with a 2.5X multiplier runs the processor at 150 MHz. Note that some processors convert the chosen CPU multiplier internally to a different multiplier. For example, some processors convert a 1.5X CPU multiplier motherboard setting to an internal 4.0X multiplier. Note also that some CPUs are named with a "performance rating" rather than their actual speed. For example, the WinChip2-300 actually runs at 250 MHz (100 MHz x 2.5), but uses the "300" name to indicate its supposed performance relative to other processors. When setting the bus speed and CPU multiplier, it is important to choose settings that run the processor at its actual rated speed rather than the labeled performance equivalent.

    You can sometimes choose between two combinations of bus speed and CPU multiplier that have the same product. In this case, choose the combination of the higher bus speed and lower multiplier, so long as the higher bus speed is supported. For example, when installing a 300 MHz processor, you can choose 66MHz/4.5X or 100MHz/3.0X. Either setting runs the processor at 300 MHz, but the latter setting provides marginally faster performance by allowing data to be communicated faster between the CPU and the external L2 cache memory.


    Different processors require different voltages. Some processors operate on a single voltage, and others (called split rail processors) require different values for Core Voltage and I/O Voltage. Old motherboards may support only one fixed voltage, and so may not be usable with recent low-voltage or dual-voltage CPUs. Pay close attention to voltage because installing a low-voltage CPU in a high-voltage motherboard may destroy the processor. Adapters are available to allow installing newer low-voltage processors in older motherboards, but in that situation it is better in every respect simply to replace the motherboard.

    Asynchronous PCI
    Systems with a 60 or 66 MHz FSB run the PCI bus at half speed—30 MHz and 33 MHz, respectively. Systems with a 100 MHz FSB run the PCI bus at one third speed—33 MHz. This process of using these fixed divisors is called synchronous PCI. But PCI devices are unreliable much above 33 MHz, and overclocking the system by using a 75, 83, or 95 MHz FSB would cause the PCI bus to run at 37.5 MHz (marginal), 41.5 MHz (unusable), or 47.5 MHz (ridiculous). So many motherboards designed to support overclocking include a jumper that allows setting the PCI bus to 33 MHz regardless of the FSB speed.
  • 2. Once you have set and verified all jumpers, lift the ZIF lever, which is located on one side of the socket, as far as it will go. If there is a processor in the socket, grasp it firmly and lift it free. It should come away without resistance.

  • 3. Locate Pin 1 on the new processor. Pin 1 is usually indicated by a dot or beveled edge on one corner of the processor, or by a missing pin on that corner. Locate Pin 1 on the ZIF socket, which is usually indicated by a dot or beveled edge, and sometimes by a numeral 1 silk-screened onto the motherboard itself. Orient Pin 1 on the new processor to Pin 1 on the socket and then gently press the processor into the socket. The processor should seat fully with little or no resistance, dropping into place because of its own weight. If the processor does not seat easily, remove it, verify that the pins align correctly, and try to seat it again. Avoid excessive force when seating the processor. It is easy to bend pins, and straightening them is next to impossible.

  • 4. Once the processor is fully seated, press the ZIF lever down until it is parallel to the edge of the socket. This locks the processor into the socket and makes electrical contact on all pins.

  • 5. If you did not previously install the cooling device, do so now. Do not forget to use thermal compound to improve heat transfer between the processor and the cooling device. Most heatsinks and heatsink/fan units clip directly to the processor or to the socket. Once you have the heatsink aligned properly with the processor (most fit properly in only one orientation) align the clip and press down until it locks into place. If your cooling unit includes a fan, attach the fan power cable to a motherboard fan power header or to an available power supply connector, as appropriate. If you are upgrading to a faster processor, do not assume that you can use the heatsink/fan unit from the original processor. Faster processors may generate more heat, and may require a more capable HSF unit. Running a newer, hotter processor with the old HSF may at best result in sporadic lockups and at worst in damaging the processor.

  • 6. Install the motherboard, if necessary, connect or reroute any cables you moved, do a quick visual once-over, reconnect the monitor, keyboard, and mouse, and then apply power to the system. The system should begin a normal boot sequence. If nothing (or something strange) happens, immediately turn the power off and reverify all connections and settings.

  • 7. Once the system boots normally, enter CMOS Setup and make whatever changes, if any, the processor documentation recommends. Once the system is working normally, turn off the power, reinstall the chassis cover, return the PC to its working location, reconnect all cables, and restart the system.

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