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Cache Coherent Interconnect

for Accelerators

CCIX® Base Specification

Revision 1.0 Version 1.0

February 15, 2019

LEGAL NOTICE

This CCIX Base Specification Revision 1.0 Version 1.0 (this “document”) is proprietary to CCIX Consortium, Inc. (sometimes also

referred to as “Company”) and/or its successors and assigns.

NOTICE TO USERS WHO ARE CCIX CONSORTIUM, INC. MEMBERS:

Members of CCIX Consortium, Inc. (“CCIX Member(s)”) may use and/or implement this CCIX Base Specification Revision 1.0

Version 1.0 subject, however, to the CCIX Member’s compliance with all of the terms and condition of the Company’s Intellectual

Property Policy, Bylaws, and all other Company policies and procedures (“CCIX Governing Documents”) and the CCIX Member’s

Participation Agreement.

Each CCIX Member hereby agrees that its use and/or implementation of this CCIX Base Specification Revision 1.0 Version 1.0 and/or

any of the specifications described herein are subject to the following additional terms and conditions:

(i) The Company takes no position regarding, and each CCIX Member is solely responsible for determining on its own, the existence,

validity, and/or scope of any intellectual property rights or any other rights (including without limitation any “Essential Claims”

under the Company’s Intellectual Property Policy) that any third party (including without limitation any other CCIX Member) may

own or otherwise hold which may (or may not) pertain to or cover any implementation or other use of this CCIX Base

Specification Revision 1.0 Version 1.0 or any specifications described herein.

(ii) Each CCIX Member is solely responsible for:

(a) determining whether any license or other consent (including without limitation any “FRAND License” under the Company’s

Intellectual Property Policy) from any third party (including without limitation from any other CCIX Member) is needed to

implement or otherwise use this CCIX Base Specification Revision 1.0 Version 1.0 or any of the specifications described

herein; and

(b) Negotiating and obtaining, for itself, any such license or other consent (including without limitation any “FRAND License”

under the Company’s Intellectual Property Policy) from any and all such third parties (including without limitation from other

CCIX Members).

NOTICE TO NON-MEMBERS OF CCIX CONSORTIUM, INC.:

If you are not a CCIX Member and you have obtained a copy of this document, you only have a right to review this document or make

reference to or cite this document. Any such references or citations to this document must acknowledge CCIX Consortium’s Inc.’s

modify, make any derivatives of, or otherwise amend the referenced portion of this document in any way without the prior express written

permission of CCIX Consortium, Inc. Nothing contained in this document shall be deemed as granting (either expressly or impliedly) to

any party that is not a CCIX Member: (ii) any kind of license to implement or use this document or any specifications described therein or

any of its contents, or any kind of license in or to any other intellectual property owned or controlled by CCIX Consortium, Inc., including

without limitation any trademarks of CCIX Consortium, Inc.; or (ii) any benefits and/or rights as a CCIX Member under any CCIX

Governing Documents.

If you are not a CCIX Member but still elect to implement this document or any of the specifications described herein, you are hereby

given further notice that your election to do so does not give you any of the rights and/or protections of CCIX Members, including without

limitation any of the rights and/or protections of CCIX Members under the Company’s Intellectual Property Policy or other CCIX

Governing Documents.

LEGAL DISCLAIMERS FOR ALL PARTIES:

THIS DOCUMENT AND ALL SPECIFICATIONS AND/OR OTHER CONTENT PROVIDED HEREIN IS PROVIDED ON AN “AS

IS” BASIS. TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW, CCIX CONSORTIUM, INC. (ALONG WITH THE

CONTRIBUTORS TO THIS DOCUMENT) HEREBY DISCLAIM ALL REPRESENTATIONS, WARRANTIES AND/OR

COVENANTS, EITHER EXPRESS OR IMPLIED, STATUTORY OR AT COMMON LAW, INCLUDING, BUT NOT LIMITED TO,

THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE, VALIDITY,

AND/OR NONINFRINGEMENT. In the event this document makes any references (including without limitation any incorporation by

reference) to another party’s (“Third Party”) content or work, including without limitation any specifications or standards of a Third Party

(“Third Party Content”), you may need to independently obtain a license or other consent from that Third Party in order to have full rights

to implement or use that Third Party Content.

Table of Contents

Chapter 1. Document Overview ................................................................................................................ 18

1.1 SPECIFICATION OBJECTIVE ......................................................................................................................... 18

1.2 TERMS AND ACRONYMS ........................................................................................................................... 18

1.3 REFERENCE DOCUMENTS .......................................................................................................................... 21

Chapter 2. CCIX Overview .......................................................................................................................... 22

2.1 INTRODUCTION ....................................................................................................................................... 22

2.2 TOPOLOGIES ........................................................................................................................................... 23

2.3 CCIX ARCHITECTURE MODEL ..................................................................................................................... 24

Components of the CCIX Architecture ........................................................................................ 25

Port Aggregation ......................................................................................................................... 27

CCIX Extended Data Rate Physical Layer ..................................................................................... 28

2.4 CCIX MANAGEMENT FRAMEWORK ............................................................................................................ 28

2.5 RAS ARCHITECTURE ................................................................................................................................. 28

2.6 ADDRESS TRANSLATION SERVICE ................................................................................................................ 28

2.7 SIGNALING HOSTS FROM ACCELERATORS ..................................................................................................... 29

2.8 ESTABLISHING TRUST WITH A CCIX ACCELERATOR ........................................................................................ 29

Chapter 3. Protocol Layer .......................................................................................................................... 30

3.1 INTRODUCTION ....................................................................................................................................... 30

CCIX Agents ................................................................................................................................. 30 5

Discovery and Enumeration ........................................................................................................ 32

Topologies ................................................................................................................................... 33

3.2 MESSAGE FIELDS ..................................................................................................................................... 34

Request Message ........................................................................................................................ 34

Snoop Message ........................................................................................................................... 36

Response Message ...................................................................................................................... 37 10

Field Descriptions ........................................................................................................................ 37

3.3 COHERENCE PROTOCOL ............................................................................................................................ 42

Cache States ................................................................................................................................ 42

Request Types ............................................................................................................................. 44

Request Responses ..................................................................................................................... 52

Snoop Requests ........................................................................................................................... 53 15

Hardware Specification Table of Contents

Snoop Responses ........................................................................................................................ 58

MiscOp Encoding ........................................................................................................................ 61

Protocol Error Report .................................................................................................................. 61

Request Cache State Transitions................................................................................................. 61

State Transitions at Snoopee ...................................................................................................... 64 5

Silent Cache State Transitions ................................................................................................... 66

Controlling the use of Evict and WriteEvictFull transactions .................................................... 67

Simultaneous Outstanding Requests ........................................................................................ 68

Request to Snoop Hazard ......................................................................................................... 68

3.4 TRANSACTION STRUCTURE ........................................................................................................................ 71

Request Transactions .................................................................................................................. 71 10

Snoop Transactions ..................................................................................................................... 75

3.5 ADDRESS, CONTROL, AND DATA ................................................................................................................. 77

Address and Data Alignment ...................................................................................................... 77

Request Attributes ...................................................................................................................... 77

Permitted Memory Type for Requests ....................................................................................... 80

Data and Byte Enables ................................................................................................................ 80 15

3.6 ORDERING .............................................................................................................................................. 84

Multi-copy Atomicity .................................................................................................................. 84

Completion Response and Ordering ........................................................................................... 85

CompAck ..................................................................................................................................... 85

Comp and Outstanding CompAck Dependency .......................................................................... 86

3.7 FLOW CONTROL AND PROTOCOL CREDITS ..................................................................................................... 86

Protocol Credits .......................................................................................................................... 86 20

Credit Exchange .......................................................................................................................... 87

3.8 MISCELLANEOUS MESSAGES ...................................................................................................................... 90

Uncredited Misc Messages ......................................................................................................... 90

Credited Misc Messages ............................................................................................................. 90

ID Namespace ............................................................................................................................. 90

Extension Fields in Misc Message ............................................................................................... 90 25

3.9 ERROR HANDLING .................................................................................................................................... 90

Error Classification ...................................................................................................................... 90

3.10 PACKET HEADER .................................................................................................................................... 91

Packet Header ........................................................................................................................... 91

Hardware Specification Table of Contents

Message Packing ....................................................................................................................... 94

3.11 MESSAGE FORMATS ............................................................................................................................... 95

Read Request ............................................................................................................................ 95

Write Request ........................................................................................................................... 95

Response without Data ............................................................................................................. 96

Response with Data .................................................................................................................. 97

Snoop ........................................................................................................................................ 98

Miscellaneous Message type .................................................................................................... 98

Request Chaining .................................................................................................................... 100

Snoop Chaining ....................................................................................................................... 101

Extension fields ....................................................................................................................... 101

3.12 OPTIONAL FEATURES AND PARAMETERS .................................................................................................. 104

CompAck Removal .................................................................................................................. 104

Partial Cache States ................................................................................................................ 104

Cache Line Size ........................................................................................................................ 105

Address Width......................................................................................................................... 105

Packet Header ......................................................................................................................... 105

Message Packing Enable ......................................................................................................... 105

Maximum Packet Size ............................................................................................................. 105

Summary of Properties ........................................................................................................... 105

3.13 MESSAGE ROUTING AND AGENT ID ASSIGNMENT ..................................................................................... 106

Message Routing ..................................................................................................................... 106

Broadcast Snoop Routing ........................................................................................................ 109

TxnID Assignment ................................................................................................................... 109

Agent ID .................................................................................................................................. 110

Target ID Determination ......................................................................................................... 111

Agent ID assignment Summary ............................................................................................... 111

3.14 MEMORY EXPANSION ........................................................................................................................... 112

Concurrent Memory Expansion .............................................................................................. 113

3.15 PORT AGGREGATION ............................................................................................................................ 113

Port Aggregation Routing ....................................................................................................... 114

3.16 TERMINOLOGY .................................................................................................................................... 115

3.17 TRANSACTION FLOW EXAMPLES ............................................................................................................. 118

Read Request with End-to-End CompAck ............................................................................... 118