Difference between revisions of "samsung/microarchitectures/m4"

	Edit Values
	Mongoose 4 µarch
	General Info
Arch Type	CPU
Designer	Samsung
Manufacturer	Samsung
Introduction	2018
Process	8 nm
	Instructions
ISA	ARMv8
	Succession
	M3 M5

Revision as of 23:54, 13 January 2019

Exynos Mongoose 4 (M4) is the successor to the Mongoose 3, an 8 nm ARM microarchitecture designed by Samsung for their consumer electronics.

Process Technology

The M4 is fabricated on Samsung's 8 nm process (8LPP).

Compiler support

Compiler	Arch-Specific	Arch-Favorable
GCC	`-mcpu=exynos-m4`	`-mtune=exynos-m4`
LLVM	`-mcpu=exynos-m4`	`-mtune=exynos-m4`

Architecture

The M4 is an incremental microarchitecture that brought a die shrink and minor enhancements.

Key changes from M3

8 nm process (from 10 nm)
ARMv8.2 (from ARMv8)
- Support for full FP16 scalar extension
- Suppot for integer dot product extension
Front end
- Larger instruction queue (48 entries, up from 40)
Back end
- LSU reorganized
- Floating-point execution units reorganized

This list is incomplete; you can help by expanding it.

Block Diagram

Individual Core

Memory Hierarchy

Cache
- L1I Cache
  - 64 KiB, 4-way set associative
    - 128 B line size
    - per core
  - Parity-protected
- L1D Cache
  - 64 KiB, 8-way set associative
    - 64 B line size
    - per core
  - 4 cycles for fastest load-to-use
  - 32 B/cycle load bandwidth
  - 16 B/cycle store bandwidth
- L2 Cache
  - 512 KiB, 8-way set associative
  - Inclusive of L1
  - 12 cycles latency
  - 32 B/cycle bandwidth
- L3 Cache
  - 4 MiB, 16-way set associative
    - 1 MiB slice/core
  - Exlusive of L2
  - ~37-cycle typical (NUCA)
- BIU
  - 80 outstanding transactions

Mongoose 1 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
  - 512-entry
- DTLB
  - 32-entry
  - 512-entry Mid-level DTLB
- STLB
  - 4,096-entry
  - Per core

BPU
- 4K-entry main BTB
- 128-entry µBTB
- 64-entry return stack
- 16K-entry L2 BTB

Core

The core of the M4 is largely the same as M3. A number of buffers have been enlarged and some of the execution units have been reorganized.

Execution engine

Floating-point cluster

The execution units on the M4 have been reorganized. In total, three new units were also added - a second FP square root unit, a second vector multiplication unit, and a new horizontal vector arithmetic unit.

Floating-point pipe changes.

Memory subsystem

This section is empty; you can help add the missing info by editing this page.

All M3 Processors

	List of M4-based Processors
	Main processor					Integrated Graphics
Model	Family	Launched	Arch	Cores	Frequency	GPU	Frequency
Count: 0

Bibliography

LLVM: lib/Target/AArch64/AArch64SchedExynosM4.td

@@ Line 94: / Line 94: @@
 == Core ==
-The core of the M4 is largely the same as {{\\|M3}}.
+The core of the M4 is largely the same as {{\\|M3}}. A number of buffers have been enlarged and some of the execution units have been reorganized.
 === Execution engine ===
 ==== Floating-point cluster ====
-{{empty section}}
+The execution units on the M4 have been reorganized. In total, three new units were also added  - a second FP square root unit, a second vector multiplication unit, and a new horizontal vector arithmetic unit.
+:[[File:m4 fp eu pipes changes.svg|thumb|left|600px|Floating-point pipe changes.]]
+{{clear}}
 ==== Memory subsystem ====
 {{empty section}}

codename	Mongoose 4 +
designer	Samsung +
first launched	2018 +
full page name	samsung/microarchitectures/m4 +
instance of	microarchitecture +
instruction set architecture	ARMv8 +
manufacturer	Samsung +
microarchitecture type	CPU +
name	Mongoose 4 +
process	8 nm (0.008 μm, 8.0e-6 mm) +

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