The present invention relates generally to a computer and more particularly to an external clock unit for use with a computer.
Digital Equipment Corporation (DEC) 6000 series computers are one type of many well known and widely used types of computers. A DEC 6000 series computer generally contains one or more central processing unit (CPU) modules, the particular number of CPU modules present in the computer depending on the particular model 6000 series computer. Each CPU module includes, in addition to a CPU, an oscillator which outputs a clock signal which sets the timing (i.e. operating speed) of the computer and a clock signal distribution chip. In the operation of the CPU module, a clock signal from the oscillator is fed into the clock signal distribution chip which distributes the clock signal where needed within the CPU module. The particular frequency of the clock signal obtained from the oscillator is dependent on the particular oscillator used in the DEC 6000 series CPU module. In one such CPU module the oscillator outputs a clock signal frequency of about 50 MHZ while in another CPU module the oscillator outputs a clock signal frequency of about 67 MHZ.
It would be desirable to be able to easily change the operating speed of a DEC 6000 series computer and more particularly to easily increase the operating speed of a DEC 6000 series computer.
Accordingly, it is an object of this invention to provide a new and improved method and apparatus for increasing the operating speed of a DEC 6000 series computer.
It is another object of this invention to provide a new and improved method and apparatus for increasing the operating speed of a DEC 6000 series computer without physically replacing the existing oscillator in the CPU module or making any other hardware changes within the computer.
It is a further object of this invention to provide a clock unit for a computer which is constructed such that it can be arranged to emit either one of two predetermined clock signals.