Engineering:Zen 4

Short description: AMD 5-nanometre processor microarchitecture

AMD Zen 4

General Info
Launched	September 27, 2022 (September 27, 2022)
Designed by	AMD
Common manufacturer(s)	TSMC
Cache
L1 cache	64 KB per core
L2 cache	1 MB per core
L3 cache	32 MB per CCD
Architecture and classification
Min. feature size	TSMC 5 nm (CCDs) TSMC 6 nm (I/O die)
Instruction set	AMD64 (x86_64)
Physical specifications
Socket(s)	Socket AM5 (LGA1718)
Products, models, variants
Product code name(s)	Desktop Raphael High-End Mobile Dragon Range Thin & Light Mobile Phoenix Server Genoa Bergamo
History
Predecessor	Zen 3
Successor	Zen 5

Zen 4 is the codename for a CPU microarchitecture by AMD, released on September 27, 2022. It is the successor to Zen 3 and uses TSMC's 5 nm process. Zen 4 powers Ryzen 7000 mainstream desktop processors (codenamed "Raphael") and will be used in high-end mobile processors (codenamed "Dragon Range"), thin & light mobile processors (codenamed "Phoenix"), as well as Epyc 7004 server processors (codenamed "Genoa" and "Bergamo").

Features

Like its predecessor, Zen 4 in its Desktop Ryzen variants features one or two Core Complex Dies (CCDs) built on TSMC's 5 nm process and one I/O die built on 6 nm. Previously, the I/O die on Zen 3 was built on GlobalFoundries' 14 nm process. Zen 4's I/O die includes integrated RDNA 2 graphics for the first time on any Zen architecture. Zen 4 marks the first utilization of the 5 nm process for x86-based desktop processors.

On desktop and server platforms, Zen 4 has moved from DDR4 to DDR5 memory; DDR4 is not supported. Additionally, Zen 4 supports new AMD EXPO SPD profiles for more comprehensive memory tuning and overclocking by the RAM manufacturers. Unlike Intel XMP, AMD EXPO is marketed as an open, license and royalty-free standard for describing memory kit parameters, such as operating frequency, timings and voltages. It allows to encode a wider set of timings to achieve better performance and compatibility. However, XMP memory profiles are still supported.

All Ryzen Desktop processors feature 24 + 4 PCIe lanes. This means that a discrete GPU can be connected by 16 PCIe lanes or two GPUs by 8 PCIe lanes each. Additionally, there are now 2 x 4 lane PCIe interfaces, most often used for M.2 storage devices. Whether the lanes connecting the GPUs in the mechanical x16 slots are executed as PCIe 4.0 or PCIe 5.0 can be configured by the mainboard manufacturers. Finally, 4 PCIe 5.0 lanes are reserved for connecting the south bridge chip or chip set.

Zen 4 is the first AMD microarchitecture to support AVX-512 instruction set extension. AVX-512 implementation is "double-pumped", where most 512-bit instructions are split in two and executed by the 256-bit SIMD execution units internally. Load and store units are also left 256-bit, preserving the throughput of up to three 256-bit memory operations, of which up to two can be stores, per cycle that was supported by Zen 3. This translates to up to one 512-bit load or store per cycle.

Other features and improvements, compared to Zen 3, include:

• L1 Branch Target Buffer (BTB) size increased by 50%, to 1.5K entries.
• L2 BTB increased to 7K entries.
• OP cache size increased by 68%, to 6.75K OPs. The OP cache is now able to produce up to 9 macro-OPs per cycle (up from 6).
• Reorder buffer (ROB) is increased by 25%, to 320 instructions.
• Integer register file increased to 224 registers, FP/vector register file increased to 192 registers. FP/vector register file widened to 512 bits to support AVX-512.
• Load queue size increased by 22%, to 88 pending loads.
• L2 cache is doubled, from 512 KiB to 1 MiB per core, 8-way.
• Automatic IBRS, where indirect branch restricted speculation mode is automatically enabled and disabled when control enters and leaves Ring 0 (kernel mode). This reduces the cost of user/kernel mode transitions.
• ~13% IPC increase on average.
• Up to 5.7 GHz max core frequency.
• Memory speeds up to DDR5-5200 are officially supported.
• In Ryzen 7000 desktop processors, integrated GPU contains two RDNA 2 CUs running at up to 2200 MHz.

Products

Desktop

On August 29, 2022, AMD announced four Zen 4-based Ryzen 7000 series desktop processors. The four Ryzen 7000 processors set to be launched on September 27, 2022 consists of one Ryzen 5, one Ryzen 7, and two Ryzen 9 CPUs and they feature between 6 and 16 cores.