Nehalem and the new Core i7

This new family of processors from Intel, called Core i7 is expected to hit

markets all over the globe anytime soon. In the tick-tock model adopted by

Intel, where each tick is a shrink of the previous microarchitecture and tock is

a brand new microarchitecture; the release of Nehalem falls in the tock part of

the cycle. It is a successor to the Core microarchitecture. Designed from the

ground up, the new design is being showcased for the first time in the Core i7

family of desktop class processors.

The new microarchitecture incorporates a number of features in its design,

resulting in what till now Intel claims, better performing and more efficient

processors. Let's have a look at some of the significant changes that these

processors come with.

Native quad-core design



One of the most important reasons why Nehalem is a radically new design for
Intel is that for the first time, the chip manufacturer is producing a 'native'

quad-core processor, where all four cores sit on the same piece of silicon,

similar to AMD's Phenom X4 CPUs. Whereas the earlier Core 2 Quad processors were

designed as multi-chip modules where two dual core processors sitting together

used to form four cores.

The advantages of having a native quad-core over an MCM are significant in

terms of processor energy efficiency, performance, and dynamic scalability.

Inclusive level 3 cache



First showcased on earlier Xeon server chips, the Core i7 family of desktop CPUs
feature up to a massive 8MB of level 3 cache (shared between all four cores) as

compared to the 2 MB of Phenom X4. The cache is also described as an inclusive

level 3 cache. Intel claims, an inclusive cache is more efficient than an

'exclusive' cache design, even if it does mean that 1MB of Nehalem's 8MB Level 3

cache is taken up by storing a copy of the 256 KB Level 2 cache inside each

processing core.

Integrated memory controller



By modularizing the design of the CPU and the Northbridge, the memory controller
has been brought to the Nehalem CPU die. The separate processing cores and

caches are linked to the on board memory controller via a new bus standard

called the QuickPath interconnect replacing the conventional front side bus. As

QuickPath replaces the Front side Bus (FSB), it also takes over the role of

allowing the CPU to connect to other system components, buses and controllers

such as the PCI Express controller and DDR3 memory, reducing latency and

improving performance considerably.

Hyper-threading



Another feature worth mentioning is Hyper-threading. Using spare resources of a
core to execute a second process thread, Hyper-threading enables a quad-core

Nehalem processor to accept and process eight threads simultaneously, making it

even more massively parallel and powerful than the current Core 2 Quad CPUs.

Note: The last three bars in both graphcs show scores obtained by the Core i7 when overclocked at different frequencies.

New socket



As the Nehalem CPU communicates directly with memory, an additional bank of

connections to the motherboard is needed. The current Socket LGA775 doesn't have

enough pins to accommodate the memory controller, so Nehalem CPUs require the

new Socket LGA1366 which has 1,366 connections to the motherboard rather than

just 775. The only drawback here is that two sockets are not compatible in any

way, so along with a new motherboard, you'll also need a new bigger CPU cooler

for Nehalem-based processors.

Grilling CORE i7



Core 2 Quad v/s Core i7 v/s Core i7 overclocked


The processor we tested was the 3.2 GHz Intel Core i7 965 Extreme edition. This
one being the fastest of all the three in the Core i7 family is also the most

expensive.

But before we could start running all benchmarks on the new processor, we

needed a benchmark for comparison. Therefore, we decided to turn this review

into a full scale battle between the Core i7 Extreme and another similar

processor, the 2.66 GHz Core 2 Quad 6700. Also, another thing that was way too

tempting and we couldn't resist doing was the idea of pushing the envelope,

better known as overclocking a processor: the Core i7 in this case. What

initially raised eyebrows, proved to be quite fruitful and informative at the

end.

The power consumption of the Core i7, both when idle or running intense applications, is less than that of Core 2 Quad.

All tests were carried first on the older Quad core to set a benchmark. Then

the Core i7 was grilled by the same procedure. And finally, after overclocking

was over, the act was repeated again a number of times.

The test bed



The bigger new chip was run on the Intel Extreme DX58SO motherboard with 4GB of
DDR3 RAM, a Sapphire Radeon 1950 XTX graphics card and a 400GB HDD at 7200 rpm

spindle speed.

A similar setup was used to run the older quad core processor. The

motherboard used for the Core 2 Quad was the Gigabyte EP 45 UD3P with 4GB DDR2

RAM and the same graphics card and HDD. In both cases 32 bit Windows Vista

Ultimate edition was used.

PC Mark 2005



The synthetic benchmark was used to start the testing process. A set of tests
were chosen that required the CPU to flex its muscles to the extreme. Core 2

Quad was the first to take a shot at the benchmark. After tests like file, audio

and image compression and other multi-threaded ones, the processor's CPU score

came out to be a decent 6415. Next, we tested the new Core i7 Extreme, which we

had high hopes from. With all new features and a native quad-core, the i7 didn't

just surpass the benchmark set by the older cousin; it literally smashed it with

a CPU score of 10,995. If this wasn't enough, the 'overclocked' i7 battered the

older CPU completely by reaching a CPU score of 13,118 when running at 4.12 GHz.

Block Diagram of the Intel X58 Express Chipset

POV Ray



Another industry benchmark, which tests the CPU's capability by rendering high
definition images with intricate details of light and shadow reflections, and

refractions. After the beating received during the PC Mark test, the Core 2 Quad

was again put to the test first. The render average for this CPU came out to be

45,010 PPS in a total of 4.37 seconds. The Core 2 Quad being a powerful desktop

class processor, the score is well, more than decent. When the same test was run

on the Core i7 the outcome managed to amaze us again. In a total time of 2.06

seconds the render average came out to be 95,325 PPS. It means in less than half

the time, we got twice the performance. When overclocked and running at 4.12

GHz, it took only 1.81 seconds to render at an overwhelming 1,13,359 PPS.

CINEBENCH Release 10



The benchmark that also checks the multi-threading capability of a processor was
no exception. The core i7 again came out to be the winner by a huge margin. When

using one CPU, Core 2 Quad scored 2163, whereas the core i7 was at 3809, and

when overclocked even a higher 4439. When using all four, the Core 2 Quad scored

6375 whereas the core i7 leaped to 15,533 and when running at 4.0GHz an even

higher 16,596. The multiprocessor speed of the Core 2 Quad was 2.95x as compared

to 4.08x of the i7. Also on the open GL standard the CPU was left behind at 101

with Core i7 scoring 172, and 203 when overclocked.

Virtualization



What might seem like an odd thing to test is actually quite important and
relevant for people who implement it. Because desktop level virtualization is

being used in the real world we couldn't ignore this area.

To get the idea of the processor's performance when running several virtual

machines, we used the CPU test of PC Mark 05 again. Using Windows Virtual PC we

made three virtual desktop systems running Windows Vista Ultimate edition (32

bit). And if that wasn't a load enough in itself, we also ran the benchmark

simultaneously on all three. The average of the three results was considered to

compare the two and as expected, the Core i7 took the cake away. The average CPU

score of the three virtual machines running on the older Core 2 Quad was 1288 as

compared to a staggering 4255 on the Core i7. Apart from scores the system

running on the Core i7 was much more responsive and lag free. We spared

overclocking the processor in this case as the load seemed overwhelming and

could lead to permanent damage to the chip.

Conclusion



We had high hopes from Nehalem. The new microarchitecture incorporates

significant new changes, therefore we expected it to perform well. But what we

did not expect was for it to give a performance that's nearly double that given

by its closest predecessor. We were also not anticipating it to hammer the Core

2 Quad while also consuming less power. Overall, it can be safely said that the

new processor is extremely powerful, consumes less power and has given desktop

performance a whole new definition.

Bottomline: The new processor, based on Nehalem

microarchitecture is extremely powerful and more power efficient than earlier

versions. The only factor that seems to bother is its steep price.