Friday, April 13, 2007

Tech Link (Mobile): Overclocking Merom: The Dell XPS M1710

A new laptop has come to town, and brings with it an overclocking monster Merom processor (Conroe's mobile brother). And the cool thing about this processor, it has higher multi unlock. This is just so hot, I want this one so bad for my AOpen i975Xa-YDG. Check it out and join me with the drool, and kudos to ExtremeTech for the great article!

Dell XPS M1710 Review
April 12, 2007

By Loyd Case
Until recently, if you wanted to overclock your laptop, you needed one with a desktop CPU. Those were pretty common in the Pentium 4 days, but we've seen fewer of them since the advent of the mobile Core 2 Duo CPUs, originally code-named Merom. A few OEMs expose settings in their BIOS setups that allow you to tweak FSB speeds, but those are pretty rare, and the clock multiplier has remained locked.

Then Dell began shipping their high-end XPS M1710 mobile PC with something they call the "Core 2 Duo T7600G." The "G" is significant, because if you order one, you get a notebook with a multiplier unlocked CPU and the ability to overclock the XPS M1710 in the BIOS setup.

In its review of the XPS M1710, PC Magazine gave the original XPS M1710 4 out of 5 stars (equivalent to an 8 out of 10 here on ExtremeTech), and liked what they saw. We took essentially the same configuration but equipped with the clock-unlocked CPU.

The purpose here is to check out performance. Obviously battery life will be seriously degraded if you push the clock rate of the CPU to its maximum overclocked setting. So we didn't run any battery life tests, though we did check to see how the system handled using SpeedStep when overclocked.

Let's take a quick tour of the XPS M1710 before diving into the benchmark numbers. Continued... The XPS M1710 is the latest iteration of Dell's high-end gaming laptops, and includes a 17-inch display with a native resolution of 1920x1200 pixels, 2GB of DDR2/667 memory and a combo DVD+/-RW-and-Blu-ray drive.

As noted earlier, this particular XPS unit arrived with an Intel Core 2 Duo T7600G multiplier unlocked. Rounding out the system's capabilities is a mobile GeForce 7950

GTX with 512MB of video memory. Windows Vista is included with this system, loaded onto an 80GB, 7200RPM hard drive.

The XPS M1710 includes a plethora of connectors—with both DVI and analog VGA for monitor connections. Also included are four USB 2.0 ports on the back, two more on the left side and a 4-pin FireWire port on the right side. Two audio jacks—one stereo output and one input—are also available. A small slot accepts SD/MMC/Sony Memory Stick flash memory cards. The M1710 supports both wired (gigabit) and wireless (802.11b/g) networking. Continued... Now that we've had a brief look at the hardware, let's take a look at the area of interest in the BIOS setup—overclocking.

You press the F2 key to get into BIOS setup. There, you'll find a comprehensive BIOS setup program, that is, comprehensive for a system from a mainstream supplier like Dell. We're interested in the section under "Performance" labeled "CPU Overclock Support."

Here you can pick a CPU clock frequency ranging from the default (2.33GHz) all the way to 3.17GHz. What you're really doing with the slider is adjusting the CPU multiplier, ranging from the default 14x all the way to 19x.

It's pretty neat that you can tweak the clock frequency so easily, though as you do so, the power usage naturally goes up. We ran three sets of tests—one at the default 2.33Ghz, another at the maximum 3.17GHz and one at the fastest "quiet" setting, which turned out to be 2.83GHz (equating to a 17x multiplier.)

This approach has the advantage of simplicity. Someone trying to dip their toes in the overclocking waters can easily make tweaks. We actually were able to run the system at the full 3.17GHz, completing out performance tests. However, the top speed has some issues, which we'll discuss shortly.

The 2.83GHz speed was the fastest speed we could set in the BIOS setup without the system fans spinning up to full speed. At 3.17GHz, the system fans were quite noisy, and had that unpleasant, high-pitched whine often associated with small cooling fans. At 2.83GHz, the system was as quiet at idle as at 2.33GHz, and even running full bore, the fan noise only stepped up slightly.

The disadvantage with this approach is that you really won't see the best possible performance. The weakness in the hardware chain is the Intel mobile 945 chipset, which supports DDR2/667 memory at best. There are no tweaks in the BIOS setup for memory speeds, nor for FSB settings. All you can adjust is the CPU multiplier. This can create imbalances between the FSB and the memory clocks.

Now that we understand how Dell permits the system to be overclocked, let's take a look at the impact on performance. Continued... We ran only a pair of benchmarks—PCMark05 and 3DMark06. There were two reasons for this: First, we were running on Windows Vista, and benchmarking on Vista is considerably more time consuming than on Windows XP. You have to let the system "settle" for a half hour after a reboot. You also need to run several conditioning runs before an actual recorded benchmark run, because of Vista's capability to optimize for frequently run applications. We saw scores in 3DMark06 increase by more than 5% after several conditioning runs and a couple of reboots.

Given that and our desire to run at three different clock speeds, the number of performance tests we could run was limited. We ran these synthetic benchmarks because they often quickly expose either stability or performance issues. With that in mind, let's take a look at our results.

Windows Experience Scores
The WEI score didn't change, no matter the CPU clock frequency, since the bottleneck wasn't the CPU. The Windows Experience Score is always the lowest of the subsystem scores. In the case of the XPS M1710, the WEI score of 4.7 was bottlenecked by system memory, which also scored 4.7.

The CPU subsystem score "out of the box" was 5.2. Curiously, the CPU subsystem score for both 2.83GHz and 3.17GHz was 5.6, further demonstrating the limitation of pushing past 2.83GHz. But the real bottleneck in this system is the relatively slow memory. Continued... PCMark05 consists of a series of synthetic benchmark suites, each designed to test an individual subsystem, such as memory, processor, and hard drive. The test auto-detects which CPU you're using and loads dynamic libraries optimized for the processor under test for each function. So an Athlon 64 would run code tweaked to run best on its architecture, while a P4 running the same test would run different code optimized for that processor. Many of the tests are small enough to fit into the large L2 caches of modern processors, so those with higher clock speeds have an advantage. It's an idealized view of performance. In the real world, application optimizations can vary widely.

With PCMark05, we do see increases in the CPU score when we jack up the multiplier, although this results in diminishing returns as you increase the clock multiplier. It's also interesting to see how the performance scales in the memory tests as well even though we're not increasing the front-side bus clock or the memory speed. Continued... Though 3DMark06 is a synthetic benchmark, it's perhaps less "synthetic" than PCMark, since it tries to simulate what goes on inside a game engine. We show here both the standard 3DMark score and the results of both 3DMark CPU tests.

Here's where we run into an interesting anomaly: The scores at the highest clock speed for the standard test are barely faster than at 2.83GHz. The CPU scores are actually lower at 3.17GHz than at 2.83GHz. This behavior is repeatable. What's going on?

Even at idle, the system fans are spinning at nearly top speed when running the system at 3.17GHz. When the 3DMark06 CPU tests kicked in, the fans got even louder, yet the scores dropped. We believe that the Core 2 Duo CPU was throttling down at some stages of the benchmark, which of course will affect performance. Continued... We all know from experience that Core 2 CPUs—even the laptop variants—often have a lot of headroom to run at higher clock speeds. So it's no surprise that Intel is starting to dip its toes in the unlocked-mobile-CPU waters. Given the space constraints of even a beefy laptop like the XPS M1710, there are limits to the cooling solutions that can be built into a compact chassis. If you consider the potential heat and power issues with overclocking, this generally means people will run an overclocked M1710 on wall power and clock back to the standard frequency when running on battery power.

Read about Overclocking Core 2 Motherboards.

The limitation of Dell's approach—allowing only multiplier adjustments—permits only one type of overclocking. It would have been interesting to have the option of altering both the FSB speed and the clock multiplier. Even so, being restricted to DDR2/667 creates another performance bottleneck, which is exacerbated as you increase the CPU multiplier.

Note that buying the XPS M1710 with the T7600G Core 2 Duo processor will cost you an extra $275. Whether the added $275 for the privilege of overclocking your laptop is worth it to you is a personal choice. Given the overall system price of $4,375, though, that added $275 is a relatively small amount.

If you're willing to forego Blu-ray and live with Windows Vista Home Premium instead of Vista Ultimate Edition, you can buy the system for about a thousand bucks less—$3,379—and still get the T7600G. That may be a more viable option for most users.

Dell and Intel should be lauded for allowing even limited overclocking. Big notebook systems like the XPS M1710 tend to get used mostly as desktop replacements, as well as LAN parties, so being connected to wall power is fairly common. We'd certainly be happy to run one of these systems at 2.83GHz all day long.

Source:Overclocking Merom: The Dell XPS M1710

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