Base 7

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Base 7
Base 7
introduction 1995
design type SPGA - ZIF
contacts 321
Bus protocol own, Intel never introduced a designation
Bus cycle Socket 7 : 50, 60, 66 MHz (unofficial: 75, 83 MHz)
Super Socket 7 : 95 and 100 MHz
Operating voltage Single-voltage or single / split-voltage, supported voltages depend on the mainboard manufacturer and supported CPUs
Processors Intel Pentium (75–200 MHz)
Intel Pentium MMX (133–233 MHz)
AMD K5 (PR75 – PR200)
AMD K6 (166–300 MHz)
AMD K6-2 / K6-2 + (266–570 MHz)
AMD K6- III / K6-III + (400–550 MHz)
Cyrix 6x86 (PR90 – PR200)
Cyrix MII (PR300 – PR433)
IDT WinChip (150–266 MHz)
Rise mP6 / mP6-II
and compatibles

The base 7 is a processor socket for the Intel Pentium and pin-compatible processors. It was originally created for the Pentium-150/166, but soon replaced socket 5 as the standard socket for slower Pentium CPUs. Socket 7 was the last socket for Intel's first generation Pentium processors . Presumably to avoid the enormous pressure of competition, Intel switched to slot 1 with its Pentium II at the beginning of 1997 , then declared socket 7 to be an entry-level platform, and then finally left it to the competition in 1998 in the desktop market and the Celeron as the new one Explaining entry-level CPU.


The base 7 had to be "adapted" several times in its history to the current conditions. These adaptations do not refer to the mechanical, but to the electrical compatibility of many motherboards with the multitude of CPU models from different manufacturers that came onto the market between 1996 and 2000. The growing number of new CPUs at that time required more and more extensive setting options for the supply voltage and frequency when operating the CPU bus and core on the motherboard. Many motherboard manufacturers recognized the trend and soon allowed setting options for CPU models on their products, which were often not even announced. And although these settings were not officially documented at first, many manufacturers submitted the information required for the operation of more modern CPUs on the support websites of their products and thus made it possible, within the scope of the available possibilities, to operate more modern CPUs on older motherboards under certain circumstances . A very popular team were, for example, the K6-III / 400 from AMD and the late models from the T2P4 series from Asus .

However, the setting options mentioned so far did not only decide whether a CPU in a mainboard ran at all or whether it was even permanently stable. Other boundary conditions were often decisive, such as the support provided by the BIOS on the motherboard or even the maximum load capacity of the installed voltage regulators. So it happened that the built-in voltage regulators seemed suitable with regard to their electrical characteristics for the high supply currents of powerful CPUs, but the cooling was not adequately dimensioned. Also, many BIOSes did not correctly recognize newer or rarely used CPUs or - even worse - could not configure them internally in such a way that they were able to exploit their full performance potential. Sometimes a combination of CPU and motherboard started up briefly, only to refuse to continue the boot process for no apparent reason during the power-on self-test . With such problems, normally only a newer BIOS version from the motherboard manufacturer could help - if they offered one at all. For motherboards whose manufacturers did not offer support, technology enthusiasts upgraded these missing capabilities in the BIOS themselves using so-called unofficial patches , e.g. B. for the K6 III + processors.

Clock frequencies

According to the specification, the socket 7 allows a bus clock of 50, 60 and 66 MHz. Intel never officially supported more than 66 MHz. Many motherboards made it possible to set bus clock frequencies of more than 66 MHz, although the chipsets used were not specified for this. Mainboards with Intel's 430HX chipset in particular often allow operation with a bus speed of up to 83 MHz. Since this chipset only allowed a fixed division of 1: 2 between the PCI and CPU bus, the PCI bus was then overclocked, which caused difficulties for a number of PCI cards. The same applies to the memory interface.

From 1996 onwards, Intel slipped more and more control of socket 7. Competing chipset manufacturers began to specify their products for bus clocks beyond 66 MHz and to support "asynchronous" modes (2: 5 and 1: 3) for PCI -Bus and / or memory interface to operate again within the specification. In addition, there were more and more Pentium-compatible CPUs such as the K5 ( AMD ) and the 6x86 ( Cyrix ). Some of them were able to hold a candle to the Pentium in some areas of application and later develop their full capabilities only with bus clocks of more than 66 MHz. This development eventually led to what is now known as Super Socket 7 and made Socket 7 less and less attractive to Intel.

Operating voltages

While Socket 4 and Socket 5 still offered very limited options for setting the operating voltages and oriented them exclusively to the needs of the Intel CPUs, the situation with Socket 7 got out of hand due to the increasing variety of Pentium-compatible CPUs. The CPUs of many manufacturers were no longer supply voltage compatible with the Intel CPUs and motherboard manufacturers had to take into account a large number of setting options. Split-voltage CPUs with two supply voltages made matters even more complex.

Variants of the base 7

A widespread view is that Socket 7 differs from its predecessor, Socket 5 , in that it supports split-voltage CPUs (such as the Pentium MMX ), in which the core and bus interface are operated with different supply voltages. Initially, however, the base 7 differed from the base 5 in the presence of a further, later two further so-called BF pins (setting the ratio of bus to CPU clock). The clock lines CLK and PICCLK were now operated at 3.3V. According to the specification, the processors were also allowed to draw more current and there had to be more space around the base for larger heat sinks.

Socket 7 with split voltage support

Adapter socket for socket 5 to support split voltage processors

At the beginning of 1997, Intel introduced the Pentium MMX, a processor that required two supply voltages. Instead of renaming the new "socket type" (the socket itself is mechanically compatible with socket 5), Intel left it with the name socket 7 . From now on, it always had to be said whether a socket 7 with or without split-voltage support was being discussed.

By using adapter sockets, socket 5 could also be made split-voltage capable. A low-drop voltage regulator is located on this adapter and provides the second supply voltage.

Super socket 7

The Super-Socket 7 is a mechanically and electrically downwardly compatible extension of the specification of the Socket 7 with split-voltage support. Basically only the time specifications for the signals of the bus interface were adjusted so that it could also be operated at 100 MHz. Since Intel neither specified nor supported this extension, the manufacturers of motherboards for the Super Socket 7 were dependent on chipsets from Intel competitors. Popular Super Socket 7 chipsets are the Aladdin V from ALi and the MVP3 from VIA Technologies .

Web links

Commons : Socket 7  - collection of pictures, videos and audio files

Individual evidence

  1. Jan Steunebrink: CPU Upgrade: Getting the AMD K6-2 + / K6-III + to work on your Super Socket 7 board. ( English ) July 2, 2008. Retrieved May 21, 2012.