Intel's Hottest Quad Core Ever: Build A QX6850 PC Without Busting Your Budget

"I think there is a world market for maybe five computers." -- Thomas J. Watson, Chairman of IBM, 1943

Watson's famous, though possibly apocryphal, aphorism, leads one to wonder just exactly how much power can reasonably fit into a single desktop PC. A blazingly fast, single-core processor, such as the 3.73-GHz Pentium Extreme Edition 965? Sure. A hot dual core from AMD or Intel? Absolutely.

What about a quad-core CPU? Though there are at least seven desktop quads to choose from (and more coming when AMD ships its Phenom quad later this year, four CPUs on the floor isn't exactly mainstream yet. Indeed, some have questioned whether any desktop really needs the power supplied by four cores chugging away.

That's what I was wondering when Intel supplied me with a test unit of its fastest CPU ever: The 3.0-GHz, Core 2 Extreme QX6850.

One thing the project resolved for me: If there were ever any questions about why one might need four processors on the desktop, they've been removed. This processor is a screamer; it's the only chip I've encountered recently -- dual cores included -- which can run a bloated modern Internet security program without the slightest noticeable delay in anything else you throw at it.

The main impetus for the build was to benchmark the QX6850, which Intel bills as a "multitasking monster delivering significantly more performance for highly threaded apps."

I put the processor through its paces using the popular Futuremark PCMark05 test suite. I fully expected that the Intel chip would show its stuff in those quantitative measurements, just as it had done in reviews at several PC enthusiast sites (see here and here).

Surprisingly, the QX6850 didn't show its full strength in the benchmarks I obtained when I put my system through its PCMark05 paces. The actual measurements I obtained (see below) were held down by my regrettable decision to skimp on the quality of the graphics card and the speed of the hard drive and memory. Subjectively speaking, though, the system performed spectacularly.

Before we get to those numbers, let me show you how I put the system together. In addition to the processor, we'll take a tour through the PC's other components. I'll also offer a bunch of tips which will help your next build, regardless of whether you go with a quad-core processor or a more mainstream dual-core device. We'll conclude with suggestions for future upgrades to the project.

In the interest of full disclosure, Intel provided the QX6850 processor and Asus shipped us a review unit of the motherboard for our project. The rest of the stuff we either paid for ourselves or scavenged from older, obsolete, or half-broken machines.

Intel hasn't yet posted full documentation for the QX6850. However, the QX6800 datasheet will get you close. Most of the specs are the same, but the QX6850 is faster. It increases the clock speed of each of the cores from 2.93 GHz to 3.0 GHz.

Most importantly, the speed of the front-side bus has been boosted from 1033 MHz to 1333 MHz. The bus is used for interprocessor communication among the four cores and also as the link between the cores and memory.

Cranking up the bus is crucial for getting maximum performance out of a multicore design. With the front-side bus approach used by Intel, each core has to "ask" for access to the bus before it can communicate with memory. That process is called "contention," for obvious reasons -- the cores must "contend" for access to the bus, and sometimes they don't get it right away. When access is delayed, it takes longer to get required instructions or data out of RAM, a situation that's called increased memory latency.

This spotlights one area where AMD has been ahead of Intel, and which the smaller chipmaker has justifiably crowed about. Namely, AMD has used integrated memory controllers in its processors since 2003, when it launched its Opteron server and Athlon desktop devices. An integrated controller connects all of a processor's cores directly to the memory, thus cutting latency to the bone and holding it there, regardless of how many cores a chip has.

Interestingly, Intel's emphasis on cranking up the speed of the bus in the QX6850 hints at a future design direction. As cores proliferate, the load on a front-side becomes more of a stumbling block against maximum performance. Accordingly, Intel is expected to go to an integrated memory controller in Nehalem, a completely new microarchitecture that will succeed the QX6850's Core architecture in late 2008.

Motherboard: Asus P5K Premium

No company makes cooler-looking mobos than Asus. They make liberal use of bypass capacitors -- a practice not always adhered to by Taiwanese motherboard makers in the early days. The caps direct any stray voltage to ground and make sure your processor stays within operating specs.

The P5K Premium board used in this project is also a harbinger of a new trend among high-end boards, in that it features built-in wireless. Personally, I prefer the assured high-speed connection of a wired link. Plus, living in an urban area, I envision wireless thieves lurking behind every lamppost. However, the feature certainly makes initial wireless set-up easier and will be welcomed by most suburban users.

Like all Asus mobos, this one is replete with cooper heat pipes. These help direct heat away from the processor and chipsets. Is this stuff really necessary? Well, a year into its life cycle, my previous build, a dual-core Athlon PC with Asus M2N32 motherboard is running just fine. That's all the more comforting, given that its processor runs hot, and I've got the box stuck in a location with poor external airflow.

Graphics Card

The Achilles' heel of this project turned out to be its $60 graphics card, an NVidia GeForce FX 5200. It's a perfectly adequate card -- Nvidia's own site characterizes it as "mainstream." However, because graphics are key factor in benchmarks, it drags down the ratings of the overall PC.

This isn't fair; if you're not using the machine for gaming, hot graphics aren't a must-have. However, it's consistent with the way ratings work these days. The canonical case is the Windows Experience Index in Vista, where your score pretty much hinges on your graphics card. For example, the PC on which I tested Vista last fall was equipped with a 3.2-GHz dual-core Pentium 940. That equated to a subscore of 4.8 on the processor portion of the Windows Experience test. However, my lowly GeForce 5200 graphics card rated only a 3.1. A fast hard drive garnered 5.2 on the disk-transfer rate subscore, and 2 Gbyte of DDR2 RAM snared a 4.5. However, the final score was 3.1, since the overall rating is determined by the lowest subscore.

Cooling

Indeed, as I got deeper into the QX6850 build, the more concerned I became about cooling issues. The QX6850 is no icebox. It has a TDP of 130 W, which is at the high end of the scale these days. As a result, I decided to devote a good chunk of time to investigate optimal cooling solutions.

I wasn't looking forward to it; processor cooling fans are about as exciting as your average oil filter. In pre-dual-core times, fans were mostly an afterthought. You hooked one up and forgot about it. Sure, a PC occasionally fried, but if you weren't overclocking, there wasn't much to worry about.

The typical fan used with a Socket 775 processor such as the QX6850 is the standard model made by Intel. The spring-loaded hold-down clips used on this fan, and many others, are difficult to seat properly. Typically, when you try to attach the fan on top of the processor, you'll get two or three of the clips to lock down into the motherboard, but the fourth one will splay out, bend, or otherwise refuse to "click." Unfortunately, at that point it's almost impossible to extract the previous three and start over.

On one sad project not too long ago, I had to force the final clip through the motherboard, and then use Crazy Glue to keep the fan from coming loose. The kludge worked -- indeed, the PC still runs just fine -- notwithstanding the fact that the glue ate away some insulation on the bottom of the mobo.

For any project, I'd recommend that builders eschew the stock Intel fan for a better alternative, which usually isn't any more expensive. One acceptable aftermarket offering is StarTech's Socket 775 Fan. The StarTech has a big plastic "X," with four posts, that you insert from the bottom side of the motherboard. Then you seat the fan on the top site, and attach it to that restraining clip via four spring-loaded screws. It's much more effective than Intel's funky clips. An additional bonus is that the fan is easily salvageable if your system breaks.

On the assumption that the Core 2 Extreme would run hotter than the average dual core, I sought out the best cooling solution for the buck. It turned out to be the $27 Freezer 7 Pro from Arctic Cooling. While the Freezer Pro has spring-loaded clips, they're better designed than the ones on the Intel 775 fans, so they seat easily. The unit also has a detachable fan, which you remove so you can get at the clips. It also comes with pre-applied lithium grease, which is crucial for a proper thermal connection between the processor and the heat sink.

Mostly, the unit just looks impressive, with the biggest darn processor heat sink you're likely to see. With the PC fired up, the Freezer Pro keeps it running near ambient (room temperature) at idle. Even when the system was cranked up, the CPU temperature rarely rose above 46 degrees C. Another minor but important point: While most modern mobos have 24-pin main power connectors, probably half of all power supplies still have the old-style, 20-pin connectors. If you get one of these, you'll have to get a 20-to-24 pin adaptor before you can fire up your system. They're only $8 or so, but the oversight isn't worth the two-day shipping wait.

A similar situation applies to the 4-pin 12V connector, which is a separate bundle of wires running out of the power supply. Some motherboards use instead a new, 6-pin PCI-E connection. However, since nearly all supplies have stuck with the old, 4-pin version, motherboards requiring the newer hook-up almost always include an adaptor.

Benchmarks: Where The Rubber Hits The Road

The benchmarks for the final system were a real disappointment. The overall PCMark05 score of 2,890 was dragged down by my anemic GeForce 5200 graphics card. A system with the same processor but equipped with a GeForce 8800-class card normally gets a PCMark05 rating of 19,119--a full order-of-magnitude greater than my box achieved. Unfortunately, the $300 minimum price tag commanded by that kind of graphics power was way beyond my budget for the project.

As well, the four-year-old 80 Gbyte Maxtor hard drive I salvaged from a half-working machine to use in this project also negatively impacted the benchmark results. Though its 5,200-rpms were fast for its day, it only loaded apps at a data rate of 6.33 Mbyte/sec.

With such pokey peripherals, it's perhaps unsurprising that my year-old dual-core system bested the Core 2 Extreme, garnering 3,981 PCMarks. How could that be? Well, even though the processor was a less powerful 2.6-GHz AMD Athlon 64 X2 5000+, it had slightly hotter graphics in the form of a GeForce 6200-class card.

The nearly 1,000 PCMarks of daylight between last year's Athlon and the new Core 2 Extreme begs the question: How did the two chips compare on the CPU-specific portion of the benchmark? In this area, the 3.0-GHz quad-core Intel came out ahead of the AMD in the key areas of file compression/decompression, file encryption/decryption, image decompression, and audio compression.

What's Left To Do?

Clearly, upgrading the graphics card is the first item on my list. A processor as powerful as the QX6850, fitted with a low-cost graphics card like the GeForce 5200 is like a fish without a bicycle.

Having a setup that allows you to select your OS upon startup renders moot the now-nine-month-old dilemma: "Windows XP or Vista?" Use the former for your mission-critical, work at home, or so-old-they-haven't-been-updated applications. Select Vista when you want to have fun or partake in the brave new Mac-like world that Microsoft is apparently intent upon carving out.

Here's an area where the spirit is willing but the body is not interested in coping with the possible spillage and carpet-damage issues. Water cooling is crucial once you get into overclocking top-of-the-line processors. Since I'm running light applications at stock speeds, I think I'll leave this one to the gameboys, for now. However, I'm willing to make a possibly outlandish prediction: Water-cooled PCs become the norm (say, half of all high-end desktops) by 2010.

Summary

The main lesson I've taken away from my dual-core build project last year, and this quad effort, is that as one's sophistication increases, so, too, does the desire to tackle increasingly complicated add-ons and ambitious from-the-ground-up builds.

As well, it's my impression that one always runs into a minor, yet annoying challenge along the way. A project which seems so promising at the start ("I'm going to build a computer just like that dream machine they put together at Maximum PC") rarely pans out that way.

In this case, poor choices made with the best intentions -- a low-cost graphics card and a salvaged hard drive, both selected to save money -- ended up sandbagging the performance of my system.

Another note on the benchmarks: Too many reviews focus on numbers, evaluating systems solely on that basis. Ultimately, a users' judgment about his or her PC is a subjective one.

Consider my three most recently built PCs, which are equipped respectively with a 2.6-GHz, dual-core Athlon 64 X2 5000+, a 3.2-GHz, dual-core Pentium D 940, and the 3.0-GHz quad-core QX6850. My interactions with all three differ from what you'd call the industry party line. For example, not many reviewers think too much of the Pentium D 940, which also has the added rap of being pretty much obsolete. Nevertheless, I think of my 940 box as the steadiest and most reliable platform I've got, the go-to system for mission-critical work.

As for the Athlon 64 X2, with AMD about to release a new architecture later this year, it's no longer at the cutting edge, either. Regardless, my year-old Athlon box is the most "fun" -- talk about a subjective judgment -- of all my PCs, if it's not as cool-running as I'd like. These days, with a 3.0-GHz Athlon 64 X2 6000+ selling for only $185, that's something to consider.

Finally, with the QX6850, clearly my benchmarks didn't match what other reviews have achieved when they've matched the processor with state-of-the-art sister components in fully outfitted labs. Nevertheless, the QX6850 is clearly the smoothest running and fastest chip I've ever used, with ample headroom for any task.

However, I think it's reasonable to ask whether it's worth spending $1,100 on a processor if you're not going to build a so-called "enthusiast" (i.e., gaming) system. Either wait until the QX6850 comes down in price, or select a worthy but lower-cost alternative, such as the $300 Core 2 Quad Q6600.

What have you learned in your PC projects and what's your vote for my next project? Drop me a line at [email protected], and let me know.