Advanced Accelerator Adapter Electro-Mechanical Specification

The Advanced Accelerator Adapter Electro-Mechanical Specification defines an electro-mechanical specification for advanced accelerator adapters within the OpenPOWER eco-system supported by IBM® POWER9™. POWER9 modules present a 25Gbps interface organized into groups of 8 bit-lanes. Innovation within the community is encouraged for systems that support accelerated computing and the accelerator adapters needed to make heterogeneous / accelerated computing solutions available to the market.

This specification defines two accelerator approaches. The first approach is a mezzanine card attached to the system planar via two connectors. This approach is defined in Part I: Mezzanine Adapter Card.

The second approach is via cable and is defined in Cabled Interface Extension. While the accelerator card form factor is not defined in this specification Part II : Cabled Interface Extension assumes a PCIe® card for illustration.

The electrical characteristics of the 25Gbps channel are defined in Part III: 25 Gbit/sec Electrical Channel.

This document is a Standard Track, Workgroup Specification work product owned by the 25G IO Interoperability Workgroup and handled in compliance with the requirements outlined in the OpenPOWER Foundation Work Group (WG) Process document. It was created using the Document Development Guide version 1.1.0. Comments, questions, etc. can be submitted to the public mailing list for this document at

Owned by : Accelerator TWG
Compliance : Test Suite & Harness
  • version 1.0 2017-11-08
    workgroup specification
  • version 0.9 2017-10-19
    Modified mezzanine card section 2.1,2., and 2.3 to reflect a reference design and connector PN
  • version 0.8 2017-08-17
    public review draft
  • version 0.7 2017-08-08
    Added section on Conformance, additional minor edits, removed Section 6.2 Mezzanine Net Model
  • version 0.6 2017-08-02
    Updates to table 5.1 about ILD, ILDB, and "moving average smoothing"
  • version 0.5 2017-08-01
    Updates from workgroup review
  • version 0.4 2017-07-20
    Updates from workgroup review
  • version 0.3 2017-06-27
    Added part on cable extender version
  • version 0.2 2017-04-27
    Review updates from Dan Dreps & Jeff Brown
  • version 0.1 2017-03-13
    Creation of electo-mechanical consolidated specification
  25gbps     25gio     accelerator     capi30     opencapi     power9     specification