Summary: After much fanfare, Intel's first quad-core CPU has finally arrived! The Core 2 Extreme QX6700 packs four processing cores running at 2.66GHz and 8MB L2 cache all in one package. But how well does it perform, and how far have we overclocked it so far? In this article we explore the performance of this CPU, as well as Dell's first quad-core XPS system, the Dell XPS 710. Read all the details inside!
While clock speed is certainly still important today, both AMD and Intel have realized that clock speed isn’t everything. After all, both companies have hit brick walls in frequency scaling with their CPU architectures in the past. This dilemma presents an interesting challenge to both companies – how do you dramatically improve CPU performance without relying on hitting higher clock speeds? The answer both have come up with is simple: integrate more processing cores into the CPU’s die. With two CPUs built into the same CPU die, the CPU can perform twice the amount of work as a conventional single-core CPU.
That’s the theory at least. Of course by now we all know that you’ve got to have software that’s capable of taking advantage of that second processing core, or else it ends up spending most of its time idling.
In 2005, dual-core processing was all the rage. Both AMD and Intel introduced CPUs with two processing cores built-in to the CPU. Initially there was a dearth of software capable of taking advantage of dual-core, but over the course of the past 12 months slowly but surely dual-core software has been steadily trickling in, particularly when it comes to audio/video encoding and 3D rendering.
Now in 2006 we see the debut of the first quad-core CPUs. Intel’s first out of the gate with today’s launch of the Core 2 Extreme QX6700, previously known by its codename “Kentsfield”. Intel had originally planned to release the Core 2 Extreme QX6700 in the first quarter of next year, but decided to move the release up by a few months to make it in time for the holidays.
By the end of the first half of next year, AMD plans to release their first quad-core CPU codenamed “Barcelona” (it has also been referred to previously as K8L), but until then they plan on relying their upcoming 4x4 platform. AMD’s 4x4 technology is expected to be released later this month, but it isn’t a quad-core CPU. Instead 4x4 is composed of two dual-core processors.
Ultimately with a 4x4 system you’ve still got four processing cores, but its spread across two processors and thus you’ll need a two-socket motherboard. (AMD can’t affordably integrate four processing cores into one CPU die until their smaller 65-nm manufacturing process is ready.) With Intel’s Core 2 Extreme QX6700, you’ve got four processing cores inside a single socket, in fact the QX6700 is compatible with most of today’s existing Core 2 motherboards…
We’ve discussed Intel’s 4-core implementation in the Core 2 Extreme QX6700 at length in previous articles, so we won’t get into the fine details here. In a nutshell Intel’s Core 2 Extreme QX6700 CPU is essentially two Core 2 Duo E6700 CPU’s that have been grafted together into one package connected by the front-side bus (FSB). You can literally see this in the following image provided by Intel:
Pictured above is a Core 2 Extreme QX6700 without its integrated heat spreader installed. With the heat spreader in place, it looks just like any other Core 2 CPU:
Each processing core inside the Core 2 Extreme QX6700 features 4MB of L2 cache (for a total of 8MB in the CPU), and the cores are clocked at 2.66GHz. (Again, the QX6700 is basically two Core 2 Duo E6700’s in one package.) Fundamentally Kentsfield is just two Conroe CPUs integrated into one package, although Intel has added a new digital thermometer that replaces the thermal diode used previously to read the CPU’s temperature. According to Intel, the new digital thermometer gives more accurate readings than the diode that was used previously.
In comparison to Intel’s Core 2 Extreme X6800, the QX6700 runs 273MHz slower, and it consumes nearly twice the power (Intel lists a TDP of 75W for the Core 2 Extreme X6800), but with four processing cores built-in, it should deliver significantly more performance than Core 2 Extreme X6800 in applications that are designed to take advantage of multi-core. Intel has provided the following list of games that are designed to take advantage of both dual-core and more than 2-core (multi-core) CPUs:
While it isn’t listed in the table above, CryTek’s Cevat Yerli has also confirmed that Crysis will take advantage of multi-core CPUs like the Core 2 Extreme QX6700.
Before we go on, here we should note that there is a difference between applications that have been programmed to take advantage of dual-core CPUs, and those that take advantage of multi-core CPUs like the Extreme QX6700. Just because a game takes advantage of dual-core doesn’t mean it will benefit from quad-core. Quake 4 for instance, the first game that’s been patched to take advantage of dual-core CPUs, doesn’t deliver any additional performance with a quad-core CPU like the Core 2 Extreme QX6700. From here on out, we’ll refer to dual-core games that only use two threads like Quake 4 as dual-threaded, and multi-core games that support multiple threads as multi-threaded.
Now that you understand the software ecosystem a little better, let’s discuss the 4-core hardware ecosystem.
As we stated on the first page, most of the Core 2 motherboards that were released earlier this year were designed with quad-core CPUs like the Intel Core 2 Extreme QX6700 in mind, all you’ll need is a BIOS upgrade and you’re good to go. In fact, we used ASUS P5W DH Deluxe for our Core 2 Extreme QX6700 testing.
That doesn’t mean that all Core 2-compliant motherboards will support Core 2 Extreme QX6700 however. Intel’s own D975XBX motherboard for instance, doesn’t support the QX6700. Intel has redesigned the board once again to support quad-core CPUs like the QX6700, the newest board has been dubbed the “D975XBX2”. This marks the second time that the D975XBX platform has had to be redesigned to accommodate a new Intel processor. Functionally, the XBX2 is similar to its predecessors, with the obvious inclusion of quad-core support. The motherboard continues to support three PCI Express graphics slots and supports ATI’s CrossFire technology, along with four SATA ports and Intel High Definition 7.1 audio.
Another popular Core 2-compliant motherboard that doesn’t support Core 2 Extreme QX6700 is ASUS’ nForce4 SLI X16-based motherboard, the P5N32-SLI SE Deluxe.
We didn’t have time to ping all the motherboard manufacturers, but the best advice we can give is to check the website of your motherboard manufacturer. Almost all of the P965 and G965 motherboards support Intel’s quad-core CPUs, and most of the 2nd generation 975X motherboards do too, we’ve also been told that NVIDIA’s nForce 5 and upcoming nForce 6-series chipsets will support quad-core computing, so the list of motherboards supported is rather extensive. For most of you all you’ll need is a simple BIOS update for Intel quad-core.
While Intel officially lists a TDP of 130W for Core 2 Extreme QX6700, nearly twice that of Core 2 Extreme X6800, we don’t think cooling the CPU will be an issue to most of you with a good aftermarket cooler. We used a Zalman CNPS7700-Cu to cool our QX6700, and didn’t run into any thermal issues. Those of you with high-end Scythe coolers in particular definitely have nothing to worry about. The CPU cooler Intel sent over with the QX6700 is largely similar to Intel’s previous reference heatsink/fan cooling unit, although the fan on the new cooler is a little more powerful.
If you haven’t noticed, Intel’s Core 2 CPUs are marvelous overclockers. Our CPU Overclocking Database is filled with Core 2 success stories. Many of you are OC’ing your processors by over 50% with no problems!
When we have a little bit more time we’ll play around with overclocking a little more, we wouldn’t be surprised if we broke 3.5GHz once we add more voltage. This was all accomplished with the Zalman CNPS7700-Cu and Arctic Silver 5 thermal paste by the way, nothing exotic like water cooling.
Dell will be one of the first OEMs with an Intel Core 2 Extreme QX6700 system available at launch. They sent over an XPS 710 system so we could check out their quad-core platform.
Dell’s next XPS system is built largely on its predecessor. Dell uses the same chassis, motherboard, and cooling, that they first introduced in the XPS 700 earlier this year. This means you’ll get an nForce 590 SLI motherboard with dual PCI Express graphics slots, four DIMMs, as well as three PCI slots. Interestingly enough, this is the same motherboard Dell uses for the Radeon X1950 XTX CrossFire cards.
The system Dell sent over is state-of-the-art. Not only did Dell include Intel’s Core 2 Extreme QX6700 CPU, they also outfitted the system with two GeForce 7950 GX2 cards for Quad SLI, 2GB of DDR2 memory, Creative X-Fi audio, and three hard drives for a total of one terabyte of storage!
The most distinctive part about the Dell system is how it’s built. The system case is built like a vault! This is easily one of the heaviest cases we’ve ever handled. You won’t want to haul the XPS 710 to a LAN party, but its case is certainly built to take punishment. The system itself relies on Intel’s BTX form factor, so the motherboard itself is oriented on the opposite end of the case and the video cards are mounted up instead of down, we found that removing expansion cards was a bit more of a hassle this way, but one look at the layout of Dell’s chassis makes it all worth it if you’re a cooling aficionado:
As you can see, Dell’s chassis on the XPS 710 is designed to act as part of the system’s cooling. The front of the case is basically one large vent for the system fan, which is designed to suck in cool air from the front of the case, where it’s then blown across the graphics card/sound card, before it exits out the back of the case. The CPU has its own ducted cooling enclosure which acts in a similar fashion: cool air comes in from the front, and goes out the back. The North Bridge and South Bridge of the system chipset are passively cooled by large aluminum heatsinks. Considering the amount of heat NVIDIA’s nForce 590 chipset puts out, it’s pretty remarkable that Dell is able to get by with just aluminum heatsinks in our opinion.
Besides the retention mechanism on the graphics slot, Dell uses two additional methods to keep the graphics card in place. A large external retention mechanism which sits at the bottom of the case and can be removed, and a third clip which attaches to the end of the graphics card to hold the card in place. Once everything is hooked up properly, your graphics card isn’t going anywhere, trust us, we tested it.
Looking higher up in the case, you’ll find four dedicated 3.5” drive bays for hard drives. The drives sit on rails, so they’re easily removable, and the SATA cables are tied down to ensure good airflow within the case. Dell also provides additional 5.25” and 3.5” drive bays on the front of the chassis in case you need additional bays for storage. These drive bays hide behind case doors like you’d see on a small form factor system.
It’s a nice touch, but in practice we found that the eject button built in to the case is a little hard to reach once the optical drive is opened.
At the top of the system is a 1 kilowatt power supply unit. That’s right, we said one kilowatt! That’s 1000 watts of power on tap for the most power-hungry hardware imaginable.
We’ve got a lot more to say about Dell’s new XPS 710 system, but we’ll save those comments for an official review to come later. Already though we’re highly impressed by the system Dell has put together, it’s powerful, fast, and best of all it runs extremely quietly. If you recall, earlier this year we took a brief look at a Quad-SLI system from Alienware, the liquid-cooled ALX. After seeing both up close, let’s just say that you Alienware fans who’ve dismissed Dell’s XPS line shouldn’t rush to judgment. Dell’s put together a pretty good system with their XPS 700 series. The XPS 710 even provides overclocking options inside BIOS for enthusiasts, in fact with a couple of keystrokes we overclocked the XPS 710 to 3.2GHz!
Although obviously you’ll void the warranty if you choose to overclock.
Dell will begin taking orders for the XPS 710 when the Core 2 Extreme QX6700 launches on Nov 14th. While the XPS 700 line got off to a rough start due to availability issues, most of those snags have now been resolved based on end user reports. The XPS 710 is essentially based on the same hardware -- the only difference is the new CPU -- so hopefully availability won't be an issue for Dell's latest XPS PC.
LAME MT MP3 Encoding (MS Compiler)
Note: Comparing the Dell to our standard Intel testbed platform is a little unfair to Dell, as the system is running a different OS and also a non-native graphics card (the system came by default with two GeForce 7950 GX2 cards, although it can be ordered with the X1950 XTX). Normally we like to wipe the drive clean when we install new hardware, but we didn’t have time to do that with the Dell. As a result, performance suffers slightly, but as you’ll see in the benchmarks, the Dell system still delivered excellent performance.
Microsoft Windows Media Encoder 9
LAME MT MP3 Encoding
While we saw no performance increase from quad-core in MP3 encoding, Cinebench 9.5 showed substantial 35% gains for quad-core. For our video encoding tests, where we take a 165MB 720p video and convert it to a smaller sub-5MB file we also saw nice gains. Conversion time was down from roughly 90 seconds with the Core 2 Extreme to 77 seconds with the Core 2 Extreme QX6700. Again, keep in mind that the Dell system is running a different OS so the results aren’t directly comparable.
3DMark is one of the few gaming apps that’s designed to take advantage of multi-threading, here we see the potential of quad-core CPUs like the QX6700. Its CPU score is nearly 2x higher than that of the Core 2 Extreme X6800.
For our gaming tests, we’re running a mixture of high and low-res testing. We realize that most of you don’t game at 800x600, so we’re including results at 1280x1024 0xAA/0xAF as well as 1600x1200 with 4xAA/8xAF, which are settings more typical of someone with a Radeon X1950 XTX card. In the low resolution tests that stress CPU performance, the Core 2 Quad and Dell XPS system perform largely identical to that of Core 2 Duo E6700, which is to be expected since F.E.A.R. doesn’t take advantage of multi-threading. As you increase screen resolution, the bottleneck shifts to the graphics card and by 1600x1200 we’re GPU-bound and all the systems deliver similar performance.
As we mentioned earlier, Quake 4 has been programmed to take advantage of two threads, but nothing more. As such, the Core 2 Extreme QX6700 system performs similarly to the Core 2 Duo E6700, as both rigs are running at the same clock speed. A little later on in this article we’re going to run our gaming tests with multiple apps running in the background to really stress the CPU. Also keep in mind that the Dell system is likely trailing so far behind because it’s running a different OS (Windows MCE) and we swapped out the stock NVIDIA cards with ATI’s X1950 XTX without reformatting and reinstalling the OS, which is standard practice we normally do, but didn’t have time to perform for this article. Considering all this, it’s still doing a good job of keeping up with the other testbed rigs in our opinion.
Call of Duty 2
While Call of Duty 2 technically supports dual threads, we’ve never seen much of a performance improvement in this game with dual-core CPUs. Therefore it’s no surprise to see both QX6700 CPUs performing similarly to Intel’s Core 2 Duo E6700.
While flight sims like Pacific Fighters tend to be more CPU-intensive, if they’re not coded to take advantage of multiple threads, you still won’t see any performance improvements from a quad-core CPU like the Core 2 Extreme QX6700. Again, the Dell system is running a different OS, and we installed the ATI drivers without reformatting the system, so we’re not surprised to see it a little behind the Core 2 QX6700 testbed we setup for testing.
While Oblivion’s AI subroutines can get pretty CPU-intensive in the city area, again we’re seeing no performance improvements from quad-core in this game.
While Valve is working on adding multi-core enhancements to Episode 2, today Lost Coast and Episode One are still single-threaded apps and thus they don’t take advantage of the latest dual-core CPUs, much less quad-core. Up next though we’re going to run our gaming benchmarks with MP3 and video encoding testing going in the background…
Typically before entering a game, most gamers will close all their open apps before launching the game. The reason is simple: more performance. But what if you could keep all your apps open, and even do a little bit of encoding while you’re getting your game on? This is what we set out to do with our multi-tasked gaming tests. With them we ran our standard suite of MP3 and WME 9 tests while also running our gaming benchmarks.
Once again the quad-core Core 2 CPUs deliver a substantial performance boost under our multi-tasked scenario. Performance nearly doubles at 800x600, the QX6700 testbed is running at 153 fps, that’s within 12% of the performance we saw earlier in F.E.A.R. benchmarking. At 1600x1200 the performance hit for the quad-core CPUs is just 1 fps from multi-tasking.
We were so surprised by the Pacific Fighters results that we ran them quite a few times, with similar results. The performance of the quad-core CPUs is astounding in Pacific Fighters. Performance is up by a factor of nearly 2.5x over the Core 2 Extreme X6800, and the margin is even greater under 1600x1200 with 4xAA/8xAF. We’re not quite sure, but based on how close the Athlon 64 systems are to the Core 2 systems, we have a feeling that these margins between the quad-core and dual-core Intel CPUs may be a little artificially high, as the Core 2 Extreme and Duo shouldn’t be that close to the AMD CPUs. Again though, we re-ran this test multiple times and the results weren’t dramatically different, so we’re publishing them as-is, but with a disclaimer that this may be a result that’s a little too high in favor of quad-core.
Under Quake 4 the quad-core CPUs still enjoy a nice lead, although it isn’t nearly as substantial as it was in other games.
Call of Duty 2
Of course, not many of you game this way, as traditionally it comes with an enormous performance hit. But with Intel’s Core 2 Extreme QX6700, you’ve got four processing cores at your disposal, so you can run multiple apps at once with significantly better performance. Sure, we did see a performance decline in gaming under this scenario at 800x600, but under the high-res testing you’re more likely to game at, the performance impact was negligible.
Basically, with the Core 2 Extreme QX6700, gaming, or running any other apps this was is not only possible, it’s quite feasible.
Applications that take advantage of more than dual threads are much more prevalent on the audio/video and 3D rendering side of the equation, and here we did see a nice performance improvement in our testing with Cinebench 9.5, and a slimmer performance gain in Windows Media Encoder 9. Performance in our MP3 encoding and DivX conversion tests were unchanged though, although that’s definitely coming.
Games that are coded to take advantage of multiple threads are coming too. Intel lists Splinter Cell: Double Agent as the first game to ship with multi-core support. We’ll definitely be testing this claim out to see if it pans out, as Intel lists games such as Call of Duty 2, and F.E.A.R. as dual-threaded, although in previous testing we’ve seen little impact of dual-core CPUs in these apps. We’ll be testing with Valve’s multi-core benchmarking app and Supreme Commander shortly as well.
Eventually there will come a day when we wonder how we got around with just one CPU core for so long. That day isn’t quite here just yet, but it’s certainly coming.
And now here comes the bad news. The price of admission for one of Intel’s Core 2 Extreme QX6700 CPUs? Try $999. For those of you who’d prefer the clock speed advantage of Intel’s Core 2 Extreme X6800, it will continue to be sold alongside the QX6700, so gamers looking for the most performance may want to opt for that processor. CPUs and systems based around the processor like Dell’s XPS 710 will be available for purchase starting November 14th, so you’ll only have to wait two more weeks to pick up a quad-core CPU. In the meantime, we’ve got quite a bit more to say about this topic, hence this is only Part 1 of the story…
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