Haswell (microarchitecture)

Lore & Background

Haswell was first demonstrated at the 2011 Intel Developer Forum, with official announcement on June 4, 2013 at Computex Taipei. Commercial sales began for manufacturers and OEMs in mid-2013, with standalone desktop chips in September 2013. The architecture was designed to optimize power savings and performance benefits from FinFET transistors on the improved 22 nm process node. Haswell launched in three major forms: desktop (LGA 1150 and LGA 2011-v3 sockets), mobile/laptop (PGA socket), and BGA versions including Haswell-H (47 W and 57 W TDP), Haswell-ULT (13.5 W and 15 W TDP for Ultrabooks), and Haswell-ULX (10 W TDP for tablets). Only certain quad-core variants and BGA R-series SKUs received GT3e integrated graphics with Intel Iris Pro 5200; other models had GT3, GT2, or GT1 graphics. Due to low power requirements, Haswell-ULT and Haswell-ULX were only available in dual-core configurations. A refresh called Haswell Refresh was released around mid-2014, offering modest clock frequency increases, supported by Intel's 9 Series chipsets. The Devil's Canyon CPUs (i5 and i7 K-series) used an improved thermal interface material called NGPTIM, reducing operating temperatures and improving overclocking potential.

Reader's Guide

Haswell's significance lies in its architectural refinements over Ivy Bridge, including a wider core with a fourth ALU, third AGU, and second BEU, deeper buffers, and higher cache bandwidth. It introduced full 256-bit AVX execution units, new instructions (AVX2, BMI1, BMI2, ABM, FMA3), and Intel Transactional Synchronization Extensions (TSX) on the Haswell-EX variant, though a bug in TSX led to its disabling via microcode update in August 2014. The fully integrated voltage regulator (FIVR) moved voltage regulation components from the motherboard onto the CPU. Performance improvements included approximately 8% faster vector processing, up to 5% higher single-threaded performance, and 6% higher multi-threaded performance compared to Ivy Bridge. However, desktop variants drew between 8% and 23% more power under load and ran around 15 °C hotter. The integrated GPU saw up to a 20% performance increase (HD4600 vs HD4000). Haswell introduced new sockets and chipsets, including LGA 1150 for desktops and LGA 2011-v3 for enthusiast-class platforms with DDR4 support. The architecture's low-power C6 and C7 sleep states required compatible power supply units. Haswell-EP server variants, released in September 2014, offered up to 18 cores and up to 45 MB of last-level cache, with cluster on die (COD) operation mode for NUMA-aware systems. The Haswell-EX variant followed in May 2015 with functioning TSX. At least one Haswell-based processor, the Pentium G3420, was still being sold.

Did You Know?

• Haswell was the first Intel microarchitecture to feature a fully integrated voltage regulator (FIVR).
• The GT3e integrated graphics variant included on-package 128 MB of embedded DRAM called Crystalwell, serving as a Level 4 cache.
• Haswell-ULT and Haswell-ULX variants were only available in dual-core configurations due to low power requirements.
• A bug in the TSX implementation on Haswell, Haswell-E, Haswell-EP, and early Broadwell CPUs led to its disabling via microcode update in August 2014.