US 5,860,109 A · Methods and apparatus for a coherence transformer for connecting computer system coherence domains

Abstract

An apparatus for facilitating the sharing of memory blocks, which has local physical addresses at a computer node, between the computer node and an external device. The apparatus includes snooping logic configured for coupling with a common bus of the computer node. The snooping logic is configured to monitor, when coupled to the common bus, memory access requests on the common bus. There is also included a snoop tag array coupled to the snooping logic. The snoop tag array includes tags for tracking all copies of a first plurality of memory blocks of the memory blocks cached by the external device. Further, there is included a protocol transformer logic coupled to the snooping logic for enabling the apparatus, when coupled to the external device, to communicate with the external device using a protocol suitable for communicating with the external device.

Claims26

Dependent claims

In a computer system having a computer node which has a common bus, a method for enabling an external device that is external to said computer node to share memory blocks having local physical addresses in a memory module at said computer node irrespective whether said external device and said common bus both employ a common protocol and irrespective whether said external device and said common bus both operate at the same speed, said method comprising:

monitoring memory access requests on said common bus through a coherence transformer;
and
obtaining, through the coherence transformer coupled to said common bus, a first copy of a first memory block having a local physical address in said memory module on behalf of said external device, said obtaining including,
receiving, using said coherence transformer, a first memory access request for said first memory block from said external device;
acquiring, using said coherence transformer, said first copy of said first memory block from said common bus;
tracking, using a tag of a snoop tag array that is part of said coherence transformer, a state and an address of said first copy of said first memory block at said external device, said state includes one of an exclusive, a shared, and an invalid states;
and
sending said first copy of said first memory block from said coherence transformer to said external device.

5 more elements

A method for sharing memory blocks having local physical addresses in a memory module at a computer node between said computer node and an external device in a computer system, said sharing being facilitated through a coherence transformer coupled between said external device and a common bus of said computer node, said coherence transformer having snooping logic for monitoring memory access requests on said common bus, said coherence transformer further having a snoop tag array for tracking all memory blocks cached by said external device, comprising:

receiving, using said coherence transformer, a first memory access request pertaining to a first memory block of said memory blocks, said first memory access request being issued by said external device;
and
servicing, using said coherence transformer, said first memory access request by obtaining on behalf of said external device said first memory block from said common bus of said computer node, thereby insulating said computer node from any protocol difference between a first protocol employed by said external device and a second protocol employed on said common bus.

Dependencies are inferred from the claim text.

Methods and apparatus for a coherence transformer for connecting computer system coherence domains

Life of this patent

Methods and apparatus for a coherence transformer for connecting computer system coherence domains

Life of this patent

Abstract

Claims26