Method and system for determining memory refresh rate

Claim 1

A computer system, comprising: system dynamic random access memory and a dynamic random access memory controller connected thereto by a memory bus, said system memory capable of being refreshed during a first access period; a central processing unit connected to said dynamic random access memory controller by a local processor bus; a bus control unit for monitoring and controlling activity on said local processor bus and on an input/output bus, said local processor, I/O and memory buses forming a system bus; circuitry for detecting if at least one input/output device having expansion dynamic random access memory incorporated therein is connected to said bus control unit by said input/output bus, said expansion dynamic random access memory requiring a second access period in which to be refreshed, said second access period being of a longer duration than said first access period; and a refresh control unit incorporating control logic for alternatively executing either (i) a first refresh cycle if no expansion dynamic random access memory is detected in the system or (ii) a second refresh cycle if expansion dynamic random access memory is detected in the system, said first refresh cycle being a faster process than said second refresh cycle.

Claim 11

A method of refreshing dynamic random access memory in a computer system including a central processing unit and further providing (i) system dynamic random access memory and (ii) optional expansion dynamic random access memory incorporated into at least one input/output device connected to the system via an input/output bus, said expansion dynamic random access memory requiring an access period in which to be refreshed which is longer than that required by said system dynamic random access memory, said method comprising the steps of: providing a single refresh control unit for all dynamic random access memory in the system for alternatively executing either a first refresh cycle or a second refresh cycle depending on whether expansion dynamic random access memory is present in the system; detecting if at least one input/output device having dynamic random access memory is connected to the system via the input/output bus; setting a binary status of an input port on said refresh control unit depending on whether or not at least one input/output device having dynamic random access memory has been detected; and executing either said first or said second refresh cycle depending upon the status of said input port.

Claim 12

A method of refreshing dynamic random access memory in a computer system including a central processing unit and further providing (i) system dynamic random access memory and (ii) optional expansion dynamic random access memory incorporated into at least one input/output device connected to the system via an input/output bus, said expansion dynamic random access memory requiring an access period in which to be refreshed which is longer than that required by said system dynamic random access memory, said method comprising the steps of: providing a single refresh control unit for all dynamic random access memory in the system for alternatively executing either a first refresh cycle or a second refresh cycle depending on whether expansion dynamic random access memory is present in the system; detecting if at least one input/output device having dynamic random access memory is connected to the system via the input/output bus; setting a binary status of an input port on said refresh control unit depending on whether or not at least one input/output device having dynamic random access memory has been detected; and executing either said first or said second refresh cycle depending upon the status of said input port.