Excavator (microarchitecture)

Lore & Background

Excavator added hardware support for new instructions including AVX2, BMI2, and RDRAND. It was designed using High Density (Thin) Libraries normally used for GPUs to reduce electric energy consumption and die size, delivering a 30 percent increase in efficient energy use. Excavator can process up to 15% more instructions per clock compared to AMD's previous core Steamroller. AMD's Fusion Controller Hub was discontinued with the release of the Carrizo series of CPUs, as it was integrated into the same die as the rest of the CPU.

Excavator-based products include the Carrizo APU for budget and mainstream desktop and mobile markets, launched in 2015 for mobile and 2018 for desktop. The Carrizo mobile APUs featured Heterogeneous System Architecture for integrated task sharing between CPUs and GPUs. Bristol Ridge and Stoney Ridge APUs followed, utilizing socket AM4 and DDR4 RAM, with up to 4 Excavator CPU cores and up to 8 third-generation GCN GPU cores, offering up to a 20% CPU performance increase over Carrizo. The Toronto APU targeted server and enterprise markets, featuring four x86 Excavator CPU core modules and a Volcanic Islands integrated GPU core, with support for HSA/hUMA, DDR3/DDR4, PCIe 3.0, and GCN 1.2.

Desktop CPU lines include the Athlon X4 845 announced in February 2016, and three more Athlon X4 9x0 CPUs launched in 2017, all in Socket AM4 with a TDP of 65W. These are APUs with their graphics cores disabled. No Excavator-based CPUs were built for high-end desktop platforms or for high-end multi-processor server platforms.

Reader's Guide

Excavator represents the culmination of AMD's Bulldozer-derived microarchitecture lineage, delivering notable improvements in instructions per clock and energy efficiency over its predecessor Steamroller. Its use of High Density Libraries from GPU design allowed a 30% increase in efficient energy use, a significant achievement on the same 28 nm process. The microarchitecture introduced support for AVX2, BMI2, and RDRAND instructions, keeping it competitive for its era. Excavator's integration of the Fusion Controller Hub into the CPU die marked a shift toward more unified system designs. The Carrizo APU's compliance with HSA 1.0 and the Bristol Ridge APUs' adoption of socket AM4 and DDR4 RAM helped AMD transition its mainstream platforms. The Toronto APU for servers and enterprise markets extended Excavator into low-power, space-efficient BGA and SoC variants, with a complete system maximum power usage of 70 W. However, Excavator did not appear in high-end desktop or multi-processor server platforms, as AMD reserved those segments for earlier Piledriver-based Opteron parts. The microarchitecture was succeeded by the Zen microarchitecture in early 2017, which marked a clean break from the Bulldozer design philosophy.

Did You Know?

• Excavator is the fourth and last microarchitecture derived from Bulldozer.
• Excavator-based Carrizo APUs are HSA 1.0 compliant.
• The Athlon X4 845 desktop CPU is an Excavator-based APU with its graphics core disabled.
• The Toronto APU for servers was available in BGA and SoC variants, with the SoC variant integrating the southbridge on the same die.