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Ares µarch
General Info
Arch Type	CPU
Designer	ARM Holdings
Manufacturer	TSMC
Introduction	February 20, 2019
Process	7 nm
Pipeline
OoOE	Yes
Speculative	Yes
Reg Renaming	Yes
Succession
Cosmos Zeus

Neoverse N1 (codename Ares) is a high-performance ARM microarchitecture designed by ARM Holdings for the server market. This microarchitecture is designed as a synthesizable IP core and is sold to other semiconductor companies to be implemented in their own chips.

History

Arm's server roadmap.

Ares was first announced by Drew Henry, Arm’s SVP and GM of Infrastructure Business Unit, at his TechCon 2018 keynote. Ares was officially unveiled on February 20, 2019.

Release Dates

Ares was officially disclosed on February 20, 2019.

Process Technology

Ares specifically takes advantage of the power and area advantages of the 7 nm process.

Architecture

The Neoverse N1 core is almost identical to the Cortex-A76 but features a number of enhancements for infrastructure workload.

• 7 nm process
• Core
  • 11-stage
  • 4-way decode
  • 8-way issue
• System architecture
  • Designed for the Coherent Mesh Network 600 (CMN-600) mesh interconnect

Block Diagram

Typical SoC

The Neoverse N1 is also expected to be integrated along with Neoverse E1 high-efficiency cores and possibly other custom IP blocks.

Individual Core

Memory Hierarchy

The Neoverse N1 has a private L1I, L1D, and L2 cache.

• Cache
  • L1I Cache
    • 64 KiB, 4-way set associative
    • 64-byte cache lines
    • SECDED ECC
    • Write-back
  • L1D Cache
    • 64 KiB, 4-way set associative
    • 64-byte cache lines
    • 4-cycle fastest load-to-use latency
    • SECDED ECC
    • Write-back
  • L2 Cache
    • 512 KiB OR 1 MiB (2 banks)
    • 8-way set associative
    • 9-11 cycle
      • 9-cycle fastest load-to-use latency
    • ECC protection per 64 bits
    • Modified Exclusive Shared Invalid (MESI) coherency
    • Strictly inclusive of the L1 data cache & non-inclusive of the L1 instruction cache
    • Write-back
  • System-level cache (SLC)
    • 1 Bank per core duplex
    • 2 MiB to 4 MiB, 16-way set associative

The Neoverse N1 TLB consists of dedicated L1 TLB for instruction cache (ITLB) and another one for data cache (DTLB). Additionally, there is a unified L2 TLB (STLB).

• TLBs
  • ITLB
    • 4 KiB, 16 KiB, 64 KiB, 2 MiB, and 32 MiB page sizes
    • 48-entry fully associative
  • DTLB
    • 48-entry fully associative
    • 4 KiB, 16 KiB, 64 KiB, 2 MiB, and 512 MiB page sizes
  • STLB
    • 1280-entry 5-way set associative

Die

N1 core

• 7 nm process
• 1 Core + L2
• 1.2 mm² die size (1C + 512 KiB L2)
• 1.4 mm² die size (1C + 1 MiB L2)
• 1 W @ 2.6 GHz (0.75 V), 1.8 W @ 3.1 W (1.0 V)

Bibliography

• Drew Henry keynote, TechCon 2018 keynote.
• Drew Henry, direct communication
• Most of the technical details were obtained directly from Arm