Intel Core i5

The Intel Core i5-4258U is a LV (low voltage) dual-core processor for large ultrabooks launched in Q2 2013. It is based on the Haswell architecture and is manufactured in 22nm. Due to Hyper-Threading, the two cores can handle up to four threads in parallel, leading to better utilization of the CPU. Each core offers a base speed of 2.4 GHz, but can dynamically increase clock rates with Turbo Boost up to 2.9 GHz for 1 or 2 active cores.

Haswell is the successor to the Ivy Bridge architecture with improvements on both GPU and CPU performance. The CPUs are produced in 22nm and offer an optimized branch prediction as well as additional execution ports, improving the performance per clock by almost 10 percent. Furthermore, new features like AVX2 and FMA should increase the performance in future applications.

Due to these architectural improvements, the performance is slightly above a similarly clocked Ivy Bridge CPU. Therefore, the Core i5-4258U is almost as fast as the older i5-3230M. However, when using new instruction sets such as AVX2 the performance can be significantly better. Thus, the CPU has sufficient power for office and multimedia purposes as well as more demanding applications.

The integrated Iris Graphics 5100 offers 40 Execution Units (EUs) clocked at 200 - 1100 MHz with Turbo Boost, making it significantly faster than the HD Graphics 4000. As a result, the Iris Graphics competes with dedicated lower mid-range graphics cards. However, even fast dual-channel memory limits the performance.

The i5-4258U is rated at a TDP of 28 W including the graphics card, memory controller, VRMs and the integrated chipset. Therefore, the CPU is suited for larger ultrabooks 14-inches or greater.

The Intel Core i5-5257U is a fast dual-core processor based on the Broadwell architecture, which has been launched in January 2015. With a TDP of 28 W, the CPU is suited for medium-sized ultrabooks and notebooks (MacBook Pro 13), whereas smaller devices will use more power efficient ULV models such as the Core i5-5200U (15 W TDP). In addition to two CPU cores with Hyper-Threading clocked at 2.7 - 3.1 GHz (2 Cores: 3.1 GHz as well), the chip also integrates an Iris Graphics 6100 GPU and a dual-channel LPDDR3-1866/DDR3L-1600 memory controller. The Core i5 is manufactured in a 14 nm process with FinFET transistors.

Architecture

Broadwell represents the "Tick" in Intel's Tick-Tock model, which means a shrink of its predecessor Haswell. The new 14 nm manufacturing process with three-dimensional FinFET transistors allows not only improvements in energy efficiency, but also a significantly smaller die size fit for more compact packages and devices.

Further advantages result from the revised microarchitecture of Broadwell. Due to its improved branch prediction, bigger buffer sizes (1500 instead of 1000 entries in the L2 TLB) and other tweaks, the performance per clock has been increased by more than 5 percent over its predecessor. There are also some new instruction set extensions designed for cryptographic applications.

Performance

Thanks to its improved architecture, the Core i5-5257U almost matches the slightly higher clocked predecessors Core i7-4558U and Core i5-4308U (Haswell, 28 W). Thus, the CPU has sufficient power even for demanding applications and multitasking.

Graphics

The integrated Iris Graphics 6100 offers 48 Execution Units (EUs) clocked at 300 - 1050 MHz. Similar to the CPU core, the GPU architecture (Intel Gen 8) has been thoroughly revised for improved performance-per-clock. In addition, the GPU benefits from faster memory speeds up to LPDDR3-1866 (Haswell: DDR3-1600). Overall, the Iris Graphics 6100 is about 20 - 25 percent faster than the former Iris Graphics 5100. Nevertheless, demanding games as of 2015 will be playable only in low or medium settings.

Broadwell is the first Intel chip to fully support DirectX 11.2 as well as OpenCL 1.3/2.0 and OpenGL 4.3. Video will output natively via DisplayPort 1.2 or HDMI 1.4a. However, the new HDMI 2.0 standard is not officially supported.

Power Consumption

The i5-5257U is rated at a TDP of 28 W including the graphics card, memory controller, VRMs and the integrated chipset. Therefore, the CPU is suited for medium-sized ultrabooks 13-inches or greater.