Browse Prior Art Database

Memory Presence Detect

IP.com Disclosure Number: IPCOM000061599D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Kelley, GA: AUTHOR

Abstract

A method is provided for automatically detecting the extent of addressable memory available to a memory storage controller or microprocessor. A memory personalization feature at the silicon-chip level can be used to determine the amount of addressable memory available for system utilization instead of a dependence on card switches or initial program load (IPL) with a memory range check. Unused address pins at the module level are tied to VSS (ground) so that at system initialization time the controller or microprocessor can interrogate address pins to detect the presence of memory by supplying VDD through a current-limiting resistor to the address pins. When the detected logical value of an address pin is 0 (pin is at VSS), the controller or microprocessor determines the extent of memory at that level to be non-existent.

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Memory Presence Detect

A method is provided for automatically detecting the extent of addressable memory available to a memory storage controller or microprocessor. A memory personalization feature at the silicon-chip level can be used to determine the amount of addressable memory available for system utilization instead of a dependence on card switches or initial program load (IPL) with a memory range check. Unused address pins at the module level are tied to VSS (ground) so that at system initialization time the controller or microprocessor can interrogate address pins to detect the presence of memory by supplying VDD through a current-limiting resistor to the address pins. When the detected logical value of an address pin is 0 (pin is at VSS), the controller or microprocessor determines the extent of memory at that level to be non-existent. Therefore, a memory socket which normally shorts to ground when empty and the short is removed when full can be used to detect empty or full memory socket positions. For example, if address pin A9 is grounded (0), then the maximum addressable memory is 256K bits; if address pin A8 is grounded, then the maximum addressable memory is 128K bits, etc. Once the extent of addressable memory is determined, the controller or microprocessor will limit its address range within the bounds of the memory availability. Likewise, this same technique can be used to detect the presence or absence of used or unused input/output channels.

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