1. Field of the Invention
The present invention relates to apparatus and a method for controlling access to expansion memory for a computer system, more particularly, for avoiding malfunctions in the computer system due to improper installation of expansion memory that has a specified operating frequency different from an operating frequency for a data transfer bus in the computer system.
2. Discussion of the Related Art
With the widespread use and diversification in the data processing of computer systems, in particular, in personal computers, there have been strong demands for increasing the data processing speed of the computer system and also for increasing the amount of data that can be processed in the computer system.
Increasing the data processing speed has been achieved by increasing the clock frequency of operation for a central processing unit (hereinafter xe2x80x9cCPUxe2x80x9d) in the computer system. It is further achieved by increasing the operating frequency of the installed data transfer bus in the computer system.
With respect to increasing the amount of data processed, this has been achieved by adding expansion memory to the installed memory in the computer system. The addition of expansion memory to a personal computer (PC) system can be achieved by installing an expansion memory card or module into a memory slot provided in the PC system.
In the same way a CPU has a particular operating frequency, a particular operating frequency is also designated for the expansion memory module. Usually, the conventional expansion memory module has an operating frequency of 66 MHz. Recently, in order to increase the operation speed, expansion memory having an operating frequency of 100 MHz has been introduced in the market.
Generally, expansion memory is supplied as a memory module or card which includes a memory body portion and a storage portion for storing attribute information including a particular operating frequency for the memory module. The attribute information storage portion of the memory module is formed by an erasable programmable read-only memory (EPROM).
The connector configuration of a memory slot for installing a memory module or card which has a operating frequency of 100 MHz (hereinafter, simply referred to as a xe2x80x9c100 MHz memory modulexe2x80x9d) has the same configuration of the memory slot for a memory module or card which has a conventional operating frequency of 66 MHz (hereinafter, simply referred to as a xe2x80x9c66 MHz memory modulexe2x80x9d).
Consequently, it is easy to install the wrong or improper expansion memory module, which has a different operating frequency from the established operating frequency for the computer system, into the memory slot. For example, even when the operating frequency for a memory bus in the PC system is established as 100 MHz, the expansion memory slot for the PC can install the 66 MHz memory module. If an improper memory module, having a different operating frequency from the established operating frequency for the memory bus, has been installed in the expansion memory slot, malfunctions would be generated due to the timing differences of the data transfer between the memory bus and the expansion memory module.
In particular, if the PC system has a plurality of expansion memory slots, installing an improper memory module, which has a different operating frequency from the established operating frequency for the PC system, could easily happen. For example, if the PC system has two expansion memory slots, both for the 66 MHz memory module, a 100 MHz memory module can erroneously be installed in either slot. If the improper memory module is installed in an expansion memory slot, the conventional computer system can potentially malfunction by mounting the wrong memory module into a memory expansion slot due to the difference of the operating frequencies between the data transferring memory bus and the added expansion memory module.
Therefore, there is a need for an apparatus and method to prevent malfunctions from occurring in the computer system if an improper memory module, having a different specified operating frequency from the operating frequency of the computer system, has been mounted in the computer system.
The system and method according to the present invention solves the aforementioned problems and defects of the conventional memory control system and method by providing for a memory control system and method for reliably achieving a memory access control when different expansion memory modules are installed in a memory slot for increasing the memory capacity for the system.
According to the present invention, a computer system is provided for controlling access to expansion memory including a plurality of slots for mounting memory modules, each having attribute information including a specified operating frequency for the memory module; a memory bus commonly coupled to the plurality of slots for exchanging data to and from the plurality of memory modules at an established operating frequency; a first logic unit configured to read each of the specified operating frequencies for each of the plurality of memory modules; a second logic unit configured to determine whether or not each of the specified operating frequencies being read by the first logic unit is in conformity with the established operating frequency for the memory bus; and a third logic unit configured to control a start examining operation of the computer system in accordance with the determination by the second logic unit.
There is also provided a method for controlling access to a set of expansion memory modules having attribute information including a respective specified operating frequency in a computer system including reading the specified operating frequency for the memory modules; comparing an operating frequency of the computer system with the specified operating frequency for the memory modules; and controlling a start operation of the computer system based on the comparison.
There is also provided a computer system comprising a mounting module for mounting a memory module having attribute information including a specified operating frequency; an exchanging module for exchanging data at an established operating frequency to and from the memory module mounted in the mounting module; a reading module for reading the specified operating frequency in the attribute information for the memory module mounted in the mounting module; a determining module for determining whether or not the read specified operating frequency for the mounted memory module is in conformity with the established operating frequency for the data exchanging module; and a controlling module for controlling a start examining operation of the computer system in accordance with the determination by the determining module.
Further, there is provided a method for controlling access to memory modules in a computer system, which includes a memory bus for coupling the memory module, including reading a specified operating frequency for the memory module mounted in the slot; determining whether or not the specified operating frequency for the memory module is in conformity with an established operating frequency for the memory bus; and controlling the operation of the memory module based on a result of the determination.
Additional objects and advantages of the invention will be set forth in the description that follows, and in part will be obvious from that description, or may be learned by practicing the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and do not restrict the present invention as claimed. The foregoing merely provides further explanation of the claimed invention. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, explain the principles of the present invention.