Intel Ivy Bridge Processors

Introduction the 3rd Generation Core Processor Family

If there's one thing we should know about Intel processor technology, it's that it progresses like clockwork. We see a new fabrication process every two years (45nm in 2008, 32nm in 2010, 22nm in 2012, and so on) accompanied by a relentless Tick Tock release schedule. For those unfamiliar with Intel parlance, let's expand on the latter.

Roughly every 12 months, Intel launches a new CPU architecture on what the manufacturer calls a 'Tick Tock' sequence. Generally speaking, the Tick refers to major architecture revamp, while the Tock insinuates a minor architecture refresh coupled with a shrink in manufacturing process.

Using recent history as a guideline, we know that Intel attempts to launch something revolutionary on a two-year cadence, and then fills the void in between by introducing a product that makes the previous best that little bit better. Applying that formula to what's new and upcoming tells us that Ivy Bridge is Sandy Bridge with sugar on top, and Haswell - a codename you'll be hearing more of in 2013 - will be formed from an entirely new microarchitecture recipe. But your interest in Intel's 2012 Tick shouldn't wane based on terminology alone, as there's more to Ivy Bridge than meets the eye.

Introducing the 22nm Tri-Gate transistor

Ivy Bridge's first claim to fame is that it ushers in Intel's 22nm Tri-Gate transistor technology. Transistors are the key active components in today's processors and their miniaturisation is regularly cited as the driving force behind modern electronic devices. Making transistors smaller allows for a greater number to be incorporated in a chip, and as Intel co-founder Gordon Moore famously predicted; the number of transistors in a chip will approximately double every 24 months.

The increase in the number of incorporated transistors is tightly linked with performance, but keeping up with Moore's Law is an engineering challenge. Die shrinks have been, and continue to be, a contributing factor to Moore's Law, but in its move to 22nm Intel is also introducing Tri-Gate technology that improves performance and efficiency.

As pictured above right, a Tri-Gate transistor features conducting channels on three sides of a vertical fin structure. This provides a larger surface area for current to flow when the gate is on, resulting in greater performance at a lower operating voltage, with the option to add multiple fins, and reduced leakage as a result of the gate squeezing out free electrons from all three sides.

According to Intel, this implementation provides an 18 per cent performance increase in gate switching over the previous 32nm process when operating at 1V. And the improvement has been a long time coming - the Tri-Gate transistor has been in development for the best part of 10 years and given the improvements discussed above, Intel will now be using this technology for all future CPUs.

Enabling efficiency

We've established that Intel's 22nm Tri-Gate transistor technology is a good thing, and that's a fact that becomes more apparent when you examine the product.

Take, for example, the previous-generation Core i7-2700K. The range-topping 32nm Sandy Bridge processor features four physical cores as well as integrated graphics, built into a 212mm² die that utilises 1.16 billion transistors. It's an impressive chip, but the 22nm Ivy Bridge equivalent - the Core i7-3770K - is far more advanced.

Here's the overview of the Ivy Bridge die. It looks seemingly-identical to the incumbent Sandy Bridge; it features the same numbers of IA cores alongside integrated graphics and a shared cache, but the shrink in fabrication process has allowed Intel to package the components in a 160mm² die carrying a meaty 1.40 billion transistors.

That's a near-25 per cent reduction in die size coupled with a 20 per cent increase in transistor count. Both the aforementioned chips run at the same core clock speeds - 3.5GHz with a maximum Turbo frequency of 3.9GHz - but the TDP is reduced from 95W for the 32nm Sandy Bridge part, to 77W for the 22nm Ivy Bridge successor. All the raw speed, but the chip as a whole is 19 per cent more efficient.

Architecture improvements

Looking at Ivy Bridge from a top-level view shows that the fundamental design goes largely unchanged. Like Sandy Bridge, Ivy makes use of a two-chip platform (CPU and PCH), with the CPU portion neatly integrating up to four IA cores, a graphics processor and a memory controller all hooked up to a ring-based interconnect that allows the multiple processors to tap into a shared last-level cache.

The chip's make-up is in keeping with existing Sandy Bridge parts, right down to the amount of integrated cache - each IA core is exclusively served by a 64KB L1 and 256KB L2 cache, with a last-level cache of up to 8MB shared across all cores, the graphics processor and system agent.

And, as expected, Sandy Bridge features such as Hyper Threading, Turbo Boost and QuickSync have all followed through to Ivy Bridge. In many ways, this is Sandy Bridge built on a 22nm process that enables higher performance and lower power consumption, but there are a couple of key improvements under the hood.

• Instruction Set Architecture Enhancements

Expanding on Sandy Bridge's implementation of double-width Advanced Vector Extensions, Ivy Bridge brings two new Float16 format conversion instructions into the mix; VCVTPH2PS and VCVTPS2PH. These support conversion between the 16-bit (compressed) floating point memory format and the 32-bit single precision formats (either 256-bit AVX or 128-bit SSE), allowing for a higher dynamic range in the same memory footprint.

In order to improve instructions per clock (IPC), Ivy Bridge also removes MOV instructions from the execution pipeline (they now take place at the register renaming stage), a next-page prefetcher has been introduced to enable prefetching across a 4K page boundary and a pipelined divider is in place to improve throughput of divide-related computations.

Don't worry if these upgrades sound unfamiliar, just know that they're designed to enable the CPU to respond to your instructions that little bit quicker.

• Added Security

Continuing to run through the underlying improvements, the Ivy Bridge architecture also introduces two new security enhancements. The first, dubbed the Digital Random Number Generator (DRNG, pictured above), is a high-speed and standards-compliant number generator used to generate cryptographic keys.

The second, dubbed Supervisory Mode Execution Protection (SMEP, pictured below) is designed to protect against Escalation of Privilege (EoP) attacks by preventing access to user mode pages when running at a higher privilege level.

• Power Improvements

In addition to the 22nm transition, Ivy Bridge has a couple of other power-saving enhancements up its silicon sleeves. These include support for low-voltage DDR3 (DDR3L) in all mobile SKUs, options for lower system agent operating voltages in ultra-low-power parts, and DDR3 power gating; enabling parts of the memory interface to be disabled when in deep C-states.

All Ivy Bridge processors also feature Power Aware Interrupt Routing (PAIR). This latest acronym encourages the CPU to route interrupt requests for optimum performance or power efficiency, with one or the other defined by a Model-Specific Register (MSR). In performance mode, the CPU would send route interrupt requests to idle cores - forcing them to wake - whereas in power efficiency mode, the requests would be sent to active cores at the expense of optimum performance.

• Configurable TDP

Continuing the focus on thermal design power, certain mobile Ivy Bridge processors will also ship with a configurable TDP. Applicable only to Ultra-Low Voltage (ULV) and Extreme Edition (EE) mobile parts, this new feature allows a processor to dynamically scale across three TDPs. For an Ivy Bridge ULV part, the nominal 17W TDP, for example, would be flanked by a low-power 13W 'TDP Down' state, and a 33W 'TDP Up' state.

New HD graphics; a bit of tick, a bit of tock

Ivy Bridge, thus far, has felt very much like a Tick in Intel's timeline - it is, in more ways than one, a Sandy Bridge chip built on a new 22nm process node with a couple of key refinements.

But there's an area in which Intel argues against its own yearly cadence; integrated graphics. According to the manufacturer, the IGP featured in Ivy Bridge processors has been improved to such an extent that its development is better described as Tick+.

Looking at the overall feature set, we can see that the Ivy Bridge IGP - packaged as Intel HD 2500 or HD 4000, depending on processor model - is a good step up from previous-generation Sandy Bridge.

The top-level HD 4000 IGP sees the number of execution units (a.k.a. shaders) jump from 12 to 16, representing a 33 per cent increase, but the second-rung HD 2500 IGP (featured in most mainstream desktop parts) will continue to offer six execution units, in keeping with Sandy Bridge's HD 2000 component.

More importantly, the Ivy Bridge IGP is armed with a wave of internal upgrades that include support for OpenCL 1.1, DirectX 11 and OpenGL 3.1, all of which allow Intel to achieve feature parity with what's available from rival AMD processors.

It's taken a while, but Intel's making steady strides in the graphics department, and it's doing so by making the IGP more efficient. In addition to adding hardware tessellation through a hull shader, a domain shader and a fixed-function tessellator, the Ivy Bridge IGP introduces faster clearing of render targets to improve Hi-Z performance, an increase in the number of threads and registers to compensate for latency, and the ability to co-issue floating-point multiply-adds (MADs), effectively doubling throughput in certain areas.

On top of all this, the built-in Wireless Display technology has been bumped up from version 2.0 to 3.0, Quick Sync video transcoding performance is said to have seen a 2x increase, and the number of supported displays has jumped from two to three. The latter makes this the first Intel processor to natively power three displays using only integrated graphics.

The new range

At launch (April 29, 2012) Intel will roll out a total of nine desktop Ivy Bridge processors, all of which are detailed in the table below. For reference's sake, we've also included relevant processors from the incumbent Sandy Bridge lines.

Which chip's for me?

Number of Processor Cores / Threads	4 / 8	4 / 4	2 / 4
Intel Turbo Boost Technology 2.0	Yes	Yes	Yes
Intel Hyper-Threading Technology	Yes	No	Yes
Intel Smart Cache	8MB	6MB	3MB
AES New Instructions (AES-NI)	Yes	Yes	No
Intel HD Graphics with DirectX 11	HD 4000	HD 2500 / HD 4000	HD 2500 / HD 4000
Performance Tuning Enabled	Yes	Yes	No
Recommended Intel Express Chipset	Z77	H77	H61

The above table illustrates the key differences between the new Core i5 and Core i7 processors, as well as the cheaper dual-core Core i3 parts that will launch later in the year.

For the third-generation desktop Ivy Bridge line, every Core i7 processor will be a quad-core part with hyper-threading, an 8MB smart cache and integrated HD 4000 graphics. Dropping down to Core i5 will take away hyper-threading and lower the amount of smart cache to 6MB, and most i5 parts will utilise the downgraded HD 2500 IGP. Core i3, when it arrives, will do so in dual-core form with hyper-threading enabled, 3MB of cache and either HD 2500 or HD 4000 graphics.

In addition to the Core branding, it's important to make note of Intel's various processor suffixes. As a general rule of thumb, here's how they work:

• No suffix - these are regular processors aimed at the mainstream
• K - any processor with a K after its name is multiplier unlocked, providing greater overclocking potential for enthusiast users
• S - officially described by Intel as "performance optimised lifestyle," processors with an S in their name feature a lower CPU base frequency and a reduced TDP
• T - officially described by Intel as "power optimised lifestyle," any chip with a T suffix features a lower CPU base frequency, a lower Turbo Boost frequency and a greatly-reduced TDP

Compatibility

Choosing the right chip for you involves a bit of thought, but choosing the right motherboard shouldn't be too difficult. As Ivy Bridge is based on the previous-generation Sandy Bridge architecture, the new third-generation Core processors continue to utilise the LGA1155 socket that many users have become familiar with.

Ivy Bridge processors will therefore slot into existing six-series motherboards (H67, P67, and Z68, though a BIOS update may be required), but to make the most of your shiny-new chip, Intel recommends pairing a third-generation Core processor with a new seven-series chipset (Z77, Z75, H77).

Performance

Although Ivy Bridge is an incremental upgrade over Sandy Bridge, reviews from leading publications have found that when comparing the last-generation Core i7-2700K with the new Core i7-3770K, CPU performance is up by roughly 10 per cent while IGP performance jumps by as much as 40 per cent. Coupled with the speed improvements, the Ivy Bridge processor is found to be 20 per cent more power efficient than its Sandy Bridge predecessor.

Summary

Ivy Bridge will at the very least be at the heart of PC technology for the remainder of 2012. Initially targeting the mid- and high-end segments, with mainstream parts soon to follow, the new third-generation Core processor family offers cutting-edge technology and a class-leading blend of high performance and energy efficiency.

Intel remains unmatched in the desktop performance stakes and the best just got a little bit better. Coinciding with this release, Scan, as always, will have a complete range of new chips and supporting motherboards available at competitive prices.