Introduction and The Core Architecture

Intel has done it! They’ve lowered power consumption and improved battery life in our third and possibly final look at the Intel Core 2 Duo mobile CPU. So is the latest CPU all it’s hyped up to be?

A month ago we showed you exclusive testing results (here) of the new Intel Core 2 Duo T7400 ‘Merom’ CPU . While those initial results showed good improvements in floating point operation, a quick test revealed that battery life (here) of the T7400 sample Intel sent us was still not ready for prime time as the Core 2 Duo should have better battery performance by design.

Just a week following that article, we released updated results using a new BIOS for the Asus Z96J whitebook laptop (see the results of that updated BIOS here). This new BIOS helped the situation somewhat by improving battery life, but the T7400 Engineering Sample we have still fell short of matching the older T2600 Core Duo CPU in power consumption. But a month has passed since we last looked at the mobile Core 2 Duo, and Intel is now ready to let the world see what their latest CPU is capable of.

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The Core 2 Duo T7600 we are looking at today is a production sample (read: very likely the same quality and performance you will get at a retailer) clocked at 2.33 GHz, slightly faster than the 2.16 GHz on the T7400 sample we tested a month ago. And what a difference a month makes! Intel has made the improvements where it counts — better power consumption which translates into better battery life! But we’re getting ahead of ourselves here, so before we jump into the review, here’s a recap of Intel’s Core architecture for those of you unfamiliar with it.

Core 2 Duo – Intel’s Core Architecture (reprinted from our Conroe article)

From a design standpoint, the T7600 is exactly like any other Core 2 Duo mobile CPU. The following is a reprint of the Core 2 Duo architecture overview Ryan originally published back in March 2006 during the IDF.

At this past spring IDF in San Francisco, Intel shared with the world much of the details behind the new Intel Core 2 Duo processors powered by Intel’s Core Architecture.  The name of the technology behind Conroe, Merom and Woodcrest, which are all codenames for processor cores, was officially named “Core Architecture” and is the basis for all the hype that has been building at Intel for months. 

Let’s see what makes the Core 2 Duo processors tick by glancing at the architecture below the hood.

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Quickly stepping through these features, we first hit on the wide dynamic execution.  While past AMD and Intel architectures ran on a three instructions per clock design, Intel’s Core 2 Duo can act on four instructions simultaneously.  If the improved Intel macro-fusion does its job properly, the Core 2 Duo can actually perform up to five instructions per cycle.  This macro-fusing technology allows the processor to take two seperate instructions, combine them into one single instruction that the CPU can handle, and perform them both at the same time, effectively increasing the amount of work that can be done.

Intel’s advanced digital media boost describes an increase in the amount of SSE calculations done per cycle in the core. With support for 128-bit multiply, add, store and load operations, the Core 2 Duo CPUs can then combine instructions to possible do more than five calculations per cycle, though this case isn’t nearly as frequent.

The ability to reorder memory operations for better performance is called smart memory access on the new Core 2 Duo processors.  Intel’s architecture has the ability to determine whether or not a memory load is going to depend on one of the preceding stores (that would essentially change the data this Data X load is going to receive).  If it does not, the architecture can move the command up to improve system performance.  If it does, the architecture has to leave it alone to prevent any kind of data accessing errors.  When this works, it can improve the out-of-order execution speed pretty dramatically and best of all, the results are transparent to the software and don’t require any compiling or coding.

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Intel ‘Conroe’ Core 2 Duo Die

Advanced smart cache is the term given to Intel’s dynamically allocated L2 cache system in place on the Core 2 Duo processor.  The amount of L2 cache that is being controlled by either core can be adjusted dynamically when one core is in need of more of it than the other.  If only a single thread is being executed in the operating system, the primary core can take more of the L2 cache and use it to lower the memory latency hit, thus preventing the ‘cache thrashing’ when cache is full and the CPU has to go to main system memory.  This can also allow for easy data sharing between cores on the CPU.

Finally, Intel’s intelligent power capability is designed to allow the system to power down and slow down as much of the processor as possible when unneeded in order to save on power and produce less heat.  First they have integrated an ultra fine grained power control system that allows them to turn off portions of either core that are not in use.  Another way Intel’s engineers saved power was by allowing the internal busses between the ALUs and other units to be turned down to the data size of the information they are working on.

If you would like even more details, diagrams and information on the Core Architecture technology, you should definitely check out Ryan’s article from IDF that covered this in much greater detail than we have here.

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