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IDF 08 SF: Intel Reveals More About Nehalem

Date: August 19, 2008
Author(s): Rob Williams

Intel opened up about their Nehalem architecture at this summer’s IDF, and while we are unable to talk about performance data, what we can talk about is of great interest. Read on as we take a brief look at Turbo Mode, HyperThreading, CPU and Memory overclocking, the triple-channel memory controller and much more.



Introduction, Turbo Mode, Memory

The first day of Intel’s Developer Forum has drawn to a close, and if I can say one thing with certainty, it’s that Nehalem has been receiving no shortage of attention. Most of it is for great reason, and so I’ll touch up on as much about the upcoming processor as I can here.

We’ve covered Nehalem in some detail in the past, but this IDF is when Intel really began taking the curtain off of what makes the new processor ‘tick’, and what we can expect for improvements. Being part of the ‘Tick’ part of the new phase, Nehalem is a rather major microarchitecture development that could very-well make current-gen CPUs look a little weak.

Like the current-gen processors from Intel, Nehalem will release different models over time that fit into different categories. The first to the market (although the first Extreme desktop processor could very-well launch at the same time) will be the server and workstation CPUs, as seen in the below photo. The high-end desktop will sit under the Core i7 label, while other mainstream and notebook CPUs will follow in time.

Intel has no desire to hold off on releasing a notebook counter-part, because the new architecture features new enhancements that make it a good CPU for all platforms, such as a robust power-saving solution, which leads us to ‘Turbo Mode’. Turbo Mode is similar in some regards to the old-school Turbo button found on your 386 computer, where pushing it will increase processor frequency or voltage.

Turbo Mode on Nehalem is interesting, because overall, the performance is degraded, but with a caveat. If a core or two are not needed at a particular time, they will be switched off. From that point, power will shift on over to the first core, essentially increasing performance in whatever’s running at the time. If you have a Quad-Core and two cores are not needed, then both Core 0 and 1 will increase in performance slightly. You shouldn’t expect amazing increases, but anything in the >>10% range seems reasonable.

Turbo Mode will -not- replace overclocking, and Intel will actually provide an option (or at least require the option in the BIOS) to disable it, as straight overclocking will prove much more sensible for those who are looking for the best-possible performance, and so Turbo Mode is somewhat needless. The nice thing, though, is that when Turbo Mode -is- in use, the CPU should actually use less power overall, given that three cores are turned off completely.

The memory situation of Nehalem is undoubtedly one of the most interesting aspects of the new architecture, and one I’ll do a lot of testing with once a chip hits our lab. The new triple-channel solution sounds odd at first, and well, it is odd, but what matters is that it’s efficient. Although Intel released no information on latency, they released information on raw bandwidth, and the differences shown is staggering.

What’s important to note is that at the same memory speed, bandwidth will be greatly improved in Nehalem over anything to precede it. Highly overclocked current-gen processors with the fastest memory on the market will not even reach what Nehalem is capable of… even with DDR3-1066 memory. So while the overall memory frequency is low (to what we are now used to), the intense performance gains negate any downside.

But again, no latency information was given, and whether or not it will effect anything is yet to be seen, and can only be exposed with some in-depth testing. So the question many are having is about using faster memory. Intel, as they always have, gives us conservative ratings, and DDR3-1066 to them is a great speed for Nehalem, as exposed by the results above. Enthusiasts will be able to use faster memory, just like they always have.

Memory Overclocking, Final Thoughts

Depending on certain factors (none of which we can state until we actually know Nehalem’s limitations), all current DDR3 memory should work fine, as long as the rest of the system allows it, such as the QPI, or whatever limitation we might run into. DDR3-2000 has been found functional on a Nehalem rig, but it leads to the new quandary of whether or not it’s even needed. Today’s applications can’t even seem to make use of available bandwidth seen on the high-end memory kits available today, so will Nehalem essentially kill what is known as high-end RAM?

It’s hard to say. Latency won’t be much helped by the increased frequency, but the raw bandwidth will be. We are already in the ‘hardcore’ zone with 33,000MB/s, but faster RAM might very-well still improve performance in certain scenarios, such as the loading of massive photo collections, video collections, or anything that really taxes almost every component in your machine.

The new IMC is so efficient, Intel claims, that if you have an X58 motherboard, for example, you can install a single stick of DDR3 and almost match the overall memory bandwidth of a current dual-channel DDR3 configuration. Adding in a second stick will increase it further, with the third stick being the best overall solution. Although many Nehalem-based motherboards will offer four DIMM slots, it will actually become more of a downgrade at that point, due to how the triple-channel IMC operates.


Nehalem Wafer – AKA: Something I failed to put under my shirt

Memory companies are already jumping on the Nehalem bandwagon, and are preparing to launch kits at the release of the new processor. It will be very common to see both 3GB and 6GB kits, although I’m sure there will be 12GB kits as well. The 3GB kits would better suit those with 32-bit operating systems, while anything higher would only function with a 64-bit one. In many regards, it only makes sense to go with 64-bit going forward. Even notebook vendors are beginning to offer Vista 64-bit by default, so it’s catching on quicker than ever.

What else can we say about Nehalem? Sadly, we can’t give specific performance comparison results, but it’s definitely not something that will truly disappoint. Like most new processor launches, it will improve performance in most areas, and excel in a few others… just like how Penryn’s added SSE4.1 instruction set helped it dominate video-related benchmarks.

Hyper-Threading as we know it on Nehalem is not that much different than what we saw on the older P4 processors, but it is enhanced overall in very small regards. Overall, it’s not a bad addition, and in most single-threaded (and even a few select multi-threaded) applications, part of the performance increase seen likely be accredited to HT.

I should also touch on the picture above. Francois Piednoel is an Intel man that likes to have fun at work, and his projects he shows off at each show prove that. In this Thermaltake chassis, he has installed a serious gaming rig, complete with water-cooling. Oh, and there’s a secondary C2D-based system as well, which is used as a secondary PC for those times when you want to use a PC and not hear the noise. That case is big, and so is Francois’ imagination.

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