Intel Core i5-2405S Review Page: 1

Intel Core i5-2405S Review


The latest in the LGA1155 line of CPUs is the i5-2405S. Whilst many processors get bigger and better with more speed, ever tinier nm processes etc, this is squarely aimed at the energy efficient, low-power end of the market.

With a TDP of only 65W and a clock speed of 2.5GHz this is either a serious attempt to lower the energy consumption of businesses or, like the famed 65W E6800, a potential powerhouse.

Let's find out which one it is shall we.

Technical Specifications

A quick glance through the specification table and we see that this is pretty much a standard Core i5 processor. We have four non-HT cores, a bit of Turbo performance boost, all very standard fare. 

The big change with the i5-2405S compared to, for example, the Core i5-2500K we use in our Sandy Bridge bench rig is the much tighter multiplier restrictions that limit overclocking potential and the obvious reduction from a TDP of 95W to 65W.

Launch DateQ2'11
Processor Numberi5-2405S
# of Cores4
# of Threads4
Clock Speed2.5 GHz
Max Turbo Frequency3.3 GHz
Bus/Core Ratio25
Instruction Set64-bit
Instruction Set ExtensionsSSE4.1/4.2, AVX
Embedded Options AvailableNo
Lithography32 nm
Max TDP65 W
Recommended Channel Price$205.00
# of Memory Channels2
Max Memory Bandwidth21 GB/s
ECC Memory SupportedNo
Processor GraphicsIntel® HD Graphics 3000
Graphics Base Frequency850 MHz
Graphics Max Dynamic Frequency1.1 GHz
Intel® Quick Sync VideoYes
Intel® InTru™ 3D Technology,Yes
Intel® Insider™Yes
Intel® Wireless DisplayNo
Intel® Flexible Display Interface (Intel® FDI)Yes
Intel® Clear Video HD TechnologyYes
Dual Display CapableYes
Max CPU Configuration1
Package Size37.5mm x 37.5mm
Sockets SupportedFCLGA1155, LGA1155
Low Halogen Options AvailableYes
Intel® Turbo Boost Technology2.0
Intel® vPro TechnologyNo
Intel® Hyper-Threading TechnologyNo
Intel® Virtualization Technology (VT-x)Yes
Intel® Virtualization Technology for Directed I/O (VT-d)No
Intel® Trusted Execution TechnologyNo
AES New InstructionsYes
Intel® 64Yes
Idle StatesYes
Enhanced Intel SpeedStep® TechnologyYes
Thermal Monitoring TechnologiesYes
Intel® Fast Memory AccessYes
Intel® Flex Memory AccessYes
Execute Disable BitYes

Intel Core i5-2405S Review Page: 2

Intel Core i5-2405S Review

The Package

Contrary to most of the CPUs we get coming through the OC3D labs the i5-2405S is a retail sample and so we have an actual box! Still, very little is different and if you've seen one processor box you've seen them all.

Intel Core i5-2405S Review     Intel Core i5-2405S Review  

In keeping with the low power ethos of the i5-2405S the provided cooler is the non-tower Intel model. It's got fins and a fan, but that's about as close to a real heat-sink as it gets.

Intel Core i5-2405S Review     Intel Core i5-2405S Review  

And here is the i5-2405S itself. Yes we know CPUs don't make for the most exciting photos in the world. All the fancy bits are under the hood and without an electron microscope to hand this is the best we can offer.

Intel Core i5-2405S Review     Intel Core i5-2405S Review

Intel Core i5-2405S Review Page: 3

Intel Core i5-2405S Review

Test Setup

Being the very latest in the Intel line it makes sense to test it upon the latest generation of motherboards.

Intel Core-i5 2405S
Gigabyte G1.Sniper 2 Z68 Motherboard
4GB Kingston Genesis 2133MHz
EVGA GTX570 with ForceWare 280.26 WHQL
Samsung Spinpoint F1
Corsair 80GB SSD as Intel Rapid Storage Technology cache
Thermalright Silver Arrow
Windows 7 x64


Fresh out of the box the Core i5-2405S is clocked at a very humble 2.5 GHz. Although the literature states it supports up to 3.3 GHz in Turbo mode this is only on a single core, and when all four cores are active the Turbo mode pushes a whole single step up to give us a still pretty feeble 2.6 GHz. However as this is such a low watt processor perhaps there is some extra to be gained with some judicious prodding.

Intel Core i5-2405S Review  

And the answer is... no. No there isn't. With all four cores enabled the CPU runs at a maximum of 3 GHz regardless of what you've specified you want it to run at, how much power headroom you've given it, or how much extra vCore you run. Not exactly a speedster which is disappointing.

Intel Core i5-2405S Review

Let's run some tests.

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Intel Core i5-2405S Review


CPU Benchmarks

Since we tested the other CPUs in the graph, AIDA64 has undergone some serious tweaks under the hood and so the zLib and AES results can't be compared and should be taken as standalone results. However the CPU Queen and PhotoWorxx results are, and the low clock-speed of the i5-2405S is clearly evident as it just about keeps up with the old i5-2300.

Memory Benchmarks

The memory tests clearly show a bit of a hole in the write speeds, either in stock or overclocked trim. Otherwise it's about where you'd expect it to be. Those read speeds are a little cause for concern, especially considering some very rapid Kingston Genesis RAM.

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Intel Core i5-2405S Review

SiSoft Sandra

Sandra has always been great at managing to separate the component being tested from the rest of the system, and so it proves once again as it puts the i5-2405S through its paces. Although in this case paces is implying a level of performance that just isn't there. Perhaps putting it through its walking frame is closer to the mark.


Since we've been running wPrime tests we've often considered moving the 32M section of the test to a different graph because modern CPUs can do it so quickly it's tough to see the sliver of blue. The i5-2405S has no such problems, giving some of the (if not the) slowest times we've seen yet. 14 seconds to do the 32M test is quite slow, taking a minute and a half longer than a stock clocked 2500K is treacle-like.

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Intel Core i5-2405S Review

3D Mark Vantage

There is a finite amount of CPU performance that you need to get a good gaming rig though, and so it proves with the Core i5-2405S. Despite it's fairly terrible performance in the synthetics, it's a decent underpinning in 3D Mark Vantage. When combined with the latest ForceWare drivers and our GTX570 it is clearly capable of good things.

3D Mark 11

The more recent 3D Mark 11 does require a more meaty CPU and the i5-2405S, although not bad, starts to show some of its limitations. When the Image Quality is ramped up to Extreme and the GPU becomes more of a factor the CPU clearly becomes less of an issue.

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Intel Core i5-2405S Review


CineBench is in the odd position of highlighting both the good and bad sides of the i5-2405S. In the CPU test it's not quick. At all. When it comes to the OpenGL test it's not quite as bad, but clearly there is only so much that the GPU can overcome.

Crysis Warhead

Nicely following our 3D Mark testing, Crysis Warhead shows that the Core i5-2405S can power our GTX570 along with enough oomph to maintain a perfectly good frame-rate. 60 FPS is more than plenty for anyone's needs. 

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Intel Core i5-2405S Review


The Intel Core i5-2405S is probably best described as a schizophrenic CPU.

Normally CPUs fall into two categories. There are those that exist solely to power the mighty gaming rigs of the enthusiast market, and those that happily bumble along in a business environment. The i5-2405S is somehow both and neither.

When compared to other Intel CPUs on the LGA1155 socket the major benefit that this has over a Core i5-2500K or similarly non-HT processor is the low TDP. Rather than sup upon 95W, the i5-2405S has a ceiling of 65W. This is obviously a boon if you happen to run a fleet of office PCs and want the lowest electricity bill/carbon footprint possible. But then in a pure 'letter writing' way almost anything will handle such a task. If you require it to do more than that, almost anything that requires a decent amount of CPU power, then the low clock-speed is a serious detriment to a smooth and efficient workflow. There is no point in saving a tiny bit of power and heat if it takes twice as long to complete each task.

So maybe it works as a gaming CPU. After all we saw in both 3D Mark tests and Crysis that, with a decent GPU, the Core i5-2405S is plentifully powerful enough to give you a decent gaming experience. Again things aren't quite as clear cut as that.

Firstly neither 3D Mark Vantage nor Crysis Warhead with zero anti-aliasing will put much strain upon your system and, as we saw in 3D Mark 11, once the detail level and so CPU Workload increases, so the 2405S starts to struggle.

Secondly, and of more obvious importance, is the price point of the Core i5-2405S. Although pricing varies a bit around the internet the Core i5-2405S is generally to be found for the same price as the Core i5-2500K. The i5-2500K is an absolute demon of a CPU. It will run at low speed, low energy if that's what you require but it will equally blaze along at an aircooled 4.8GHz on almost any motherboard. The Core i5-2405S has the low energy bit handled like a champ, but it barely overclocks and at stock is pretty damn slow. So you save almost nothing by buying a much slower CPU for the same amount of money.

All in all about the only people who could possibly be interested in the Core i5-2405S are those who want a low-power CPU for an HTPC or plan on doing nothing more stressful than browsing the internet. If you game, the 2500K is the same money and an infinitely better buy. If you're in business then there are a plethora of low-power CPUs around that will run Word and the like for a lot less money than this.

This is exactly the type of CPU that will turn up in your local PC World. Sure 2.5 GHz of Quad Core energy-efficient power sounds great when told to someone who thinks PCs still have floppy drives. For everybody else there are other options that are better in any department you care to measure.

Thanks to Intel for providing the Core i5-2405S for review. Discuss in our forums.