The growth of data processed and stored, and the new ways that computers are being used, are causing memory capacity and performance requirements to balloon. Near Memory, the memory connected directly to a processor’s pins, must grow larger and faster to keep pace. However, industry’s response with the DDR bus and High Bandwidth Memory (HBM) failed to meet the needs of Near Memory while the newly introduced bus standards (CAPI in 2014, OpenCAPI, CCIX, and Gen-Z in 2016, and CXL in 2019) only solved memory size with slower access to Far Memory. None of these satisfy the need for larger Near Memories with high bandwidths and low latencies other than OMI.

Specification LRDIMM DDR4 DDR5 HBM2E(8-High) OMI
Protocol Parallel Parallel Parallel Serial
Signalling Single-Ended Single-Ended Single-Ended Differential
I/O Type Duplex Duplex Simplex Simplex
Paths/Channel (Read/Write) 64 32 512R/512W 8R/8W
Data Transfer Rate 3,200MT/s 6,400MT/s 3,200MT/s 32,000MT/s
Channel Bandwidth (R+W) 25.6Gbytes/s 25.6Gbytes/s 400Gbytes/s 64Gbytes/s
Latency 41.5ns 60.4ns 45.5ns
Channels / Processor Die 8 (EPYC Rome IO) 5 (NVidia Ampere) 16 (POWER10)
Processor Die Size 416mm² 826mm² 602mm²
Driver Area / Channel 7.8mm² 3.9mm² 11.4mm² 2.2mm²
Bandwidth / mm² 3.3GBytes/s/mm² 6.6GBytes/s/mm² 35GBytes/s/mm² 29.6GBytes/s/mm²
Max Capacity / Channel 64GB 256GB 16GB 256GB
Connection Multi Drop Multi Drop Point-to-Point Point-to-Point
Data Resilience Parity Parity Parity CRC
OMI Bandwidth Capacity Chart

If you have questions or want more details on this graph, contact the OCC Technical Director.

OMI is a highly tuned bus that was developed for near memory and is easily migratable to emerging memory solutions (e.g., Storage Class Memory). This serial coherent bus, a subset of OpenCAPI, was architected specifically for the interface between a processor and Near Memory having absolute minimum latency with significant bandwidth and capacity.  OMI is the solution to our evolving industry’s demand for Near Memory as data centers evolve from compute centric to becoming data centric.

What the Analysts have to say about OMI

The Future of Low-Latency Memory, Why Near Memory Requires a New Interface

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Download White Paper

1. OMI vs OpenCAPI

2. OMI Overview

3. OMI Reference Material

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The International Conference on Supercomputing (ISC21)

“Decoupling Compute from Memory, Storage and IO with OMI” – Allan Cantle

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If AMD Adopted OMI in their EPYC Architecture – Allan Cantle

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Shared-Memory Centric Computing with OMI & CXL – Democratized Domain Specific Computing – Allan Cantle

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OMI – Open Memory Interface – The Missing Piece of a Disaggregated Modular, Flexible & Composable Computing World – Allan Cantle

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OMI – Collection of Facts

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A Complete Re-Think for Memory Configurations

OpenPOWER Summit 2021

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