Nehalem is the codename of the new Intel CPU with integrated memory controller that will reach the market next month and that will be called Core i7; this architecture will also be used on CPUs targeted to servers (Xeon) and, a few years from now, it will also be used on entry-level CPUs. CPUs based on this architecture will have an embedded memory controller supporting three DDR3 channels, three cache levels, the return of Hyper-Threading technology, a new external bus called QuickPath and more. In this tutorial we will explain what’s new on this architecture.
Below we summarized a list of Nehalem main features, and we will explain what they mean in the next pages:
- Based on Intel Core microarchitecture.
- Two to eight cores.
- Integrated DDR3 triple-channel memory controller.
- Individual 256 KB L2 memory caches for each core.
- 8 MB L3 memory cache.
- New SSE 4.2 instruction set (seven new instructions).
- Hyper-Threading technology.
- Turbo mode (auto overclocking).
- Enhancements to the microarchitecture (support for macro-fusion under 64-bit mode, improved Loop Stream Detector, six dispatch ports, etc).
- Enhancements on the prediction unit, with the addition of a second Branch Target Buffer (BTB).
- A second 512-entry Translation Look-aside Buffer (TLB).
- Optimized for unaligned SSE instructions.
- Improved virtualization performance (60% improvement on round-trip virtualization latency compared to 65-nm Core 2 CPUs and 20% improvement compared to 45-nm Core 2 CPUs, according to Intel).
- New QuickPath Interconnect external bus.
- New power control unit.
- 45 nm manufacturing technology at launch, with future models at 32 nm (CPUs codenamed “Westmere”).
- New socket with 1366 pins.
It is important to remember that Core 2 CPUs manufactured under 45-nm technology have extra features compared to the Core 2 CPUs manufactured under 65-nm technology. All these features are present on Nehalem-based CPUs are the most significant ones are:
- SSE4.1 instruction set (47 new SSE instructions).
- Deep Power Down Technology (only on mobile CPUs, also known as C6 state).
- Enhanced Intel Dynamic Acceleration Technology (only on mobile CPUs).
- Fast Radix-16 Divider (FPU enhancement).
- Super Shuffle engine (FPU enhancement).
- Enhanced Virtualization Technology (between 25% and 75% performance improvement on virtual machine transition time).
Now let’s discuss in details the most significant differences introduced by this new architecture.