Verdict: Arguably, the perfect chip for power-hungry enthusiasts
It's funny when you think about it, but regardless of how fast or how cleverly a Pentium 4 or Athlon 64 can process instructions, they're fundamentally no different from the first PC processor, the Intel 8086. Despite an Athlon 64 having 105.9 million transistors, compared to an 8086's mere 29,000, it can still only carry out one task at a time.
So how do you get a CPU to work faster if it can only do one thing at a time? The most obvious answer is to increase its clock frequency, which is why, for the last seven years, Intel and AMD have been playing a game of one-upmanship by releasing faster processors, many of which were so fast they could never be produced in enough volume to satisfy demand. This period of time has been somewhat affectionately coined the 'megahertz wars', and in truth, has been one of the main driving forces behind the whole PC industry for almost a decade.
The trouble is that the faster a CPU runs, the more power it consumes and the more waste heat it produces. Running contrary to this is the limit of how big a PSU, or how noisy a cooling system most of us will accept. Faster CPUs also need to be made using smaller transistors, which creates other tricky engineering problems that hamper development. So herein lies the problem that both Intel and AMD are stuck with - the only way the two companies know how to make faster CPUs has been to clock them higher. But due to physical limitations, this method has at long last run out of steam, and Intel and AMD are stuck, unable to produce faster CPUs. You'll never see a 4GHz Pentium 4e, for example. It's official guys, the 'megahertz wars' are over, full stop.
However, the CPU industry is a belligerent place and just as one war ends, so another begins. If you can't make a single CPU core run faster, then the most obvious solution is to employ a second CPU core and run it in parallel. The idea is that a CPU with multiple cores can process more than one thread at a time, so each core doesn't need to run so fast (and hot). Theoretically, this means a multicore CPU will produce less energy than a high-frequency single-core CPU.
SPECIFICATIONS
The Intel Pentium Extreme Edition 840 is the first dual-core CPU to be let loose from Intel's labs, and Custom PC is the first magazine in the UK lucky enough to get its grubby little mitts on one. So, as you can probably gather, we were pretty damn excited to get such an early look at this next-generation CPU. The Extreme Edition is Intel's new flagship chip, but there will actually be two dual-core desktop CPUs: the Pentium D with two cores, and the Pentium Extreme Edition with two cores, each with Hyper-Threading. Put simply, this means that Windows and Linux will see four processors available for duty when using an Extreme Edition CPU!
However, although the 840 is the first of a new generation of dual-core CPUs, it's actually just two NetBurst architecture cores (Pentium 4 and Xeon) in a single package. Each core is clocked at 3.2GHz and equipped with 28KB of Level 1 cache and 1MB of Level 2 cache, the same as a 5xx series Pentium 4e. All the latest and greatest features are supported, including SSE3, EM64T (so it's also compatible with Windows XP x64 Edition), Enhanced SpeedStep and Execute Disable Bit. But, unlike the 3.73GHz Pentium 4 Extreme Edition, which has a 1,066MHz FSB, the 840 has only an 800MHz FSB, which is shared by both cores.
Since the 840 has two cores, both based on the existing NetBurst architecture, it gets hotter than a 6xx-series Pentium 4, boasting a Thermal Design Power (TDP) of 130W, compared to 119W for the hottest Pentium 4e. This may appear to contradict the whole theory of multicore CPUs (lower energy consumption and production), but to match the 840's performance in multithreaded applications, a single-core CPU would have to run stupidly fast and therefore unfeasibly hot - so hot that it would probably require phase-change cooling as a minimum.
Another issue is that it will be extremely expensive for Intel to produce 840s, because both cores are manufactured together. This means that if one core is faulty then both have to be thrown away. Future multicore Intel processors, such as the 'Presler' CPU, will also have two cores, but each core will be manufactured separately and then assembled together into a single CPU. This means Presler will be much cheaper to manufacture, and therefore significantly cheaper than an 840 when it's launched next year.
INFASTRUCTURE
Despite having about 230 million transistors, the 840 still uses the LGA775 package, although once again you'll have to change your motherboard. That's because the 840 requires a motherboard with Intel's 955X chipset or Nvidia's nForce4 SLI Intel Edition chipset. Our CPU arrived in an Intel D955XBK motherboard, which was equipped with the Intel 955X chipset. Other than dual-core support, the 955X improves on the 925XE by increasing the maximum supported DDR2 frequency from 533MHz to 667MHz. However, it's still backwards compatible with 5xx- and 6xx-series Pentium 4s, and 1,066MHz FSB Pentium 4 Extreme Edition CPUs. Also new is the ICH7R Southbridge, which adds S-ATA II support.
Our test kit came with the reference Intel HSF, which was perfectly able to keep our 840 running at full whack, although it did get extremely hot. So if you're upgrading from an older LGA775 system then you'll almost certainly have to invest in some new cooling hardware, or be prepared to accept a much noisier system. At least there are a fair number of LGA775-compatible HSFs, waterblocks and phase-change blocks on the market now.
That said, something you'll almost certainly have to invest in is a new PSU, as dual-core motherboards require an EPS12V PSU. This is the same type of PSU as those used for Xeon and Opteron motherboards, and comprises a 24-pin ATX connector and 8-pin EPS12V connector in addition to the usual Molex, floppy, S-ATA and PCI-E power plugs. ESP12V-compliant PSUs are generally quite a bit more expensive than standard ATX PSUs, so don't forget to set aside a little more of your budget than you'd expect.
PERFORMANCE
Assessing the performance of the 840 is in many ways very simple, because it's essentially two Pentium 4/Xeon-style cores in one chip. As with a true dual-processor system, the second core only really comes into its own when you're running multithreaded applications or are multitasking. Unfortunately, this is where it gets tricky, because the vast majority of mainstream (meaning non-server and workstation) applications are not multithreaded. This means that most of the applications and games you're likely to run on the 840 will perform pretty much as if you had a single 3.2GHz Pentium 4e.
However, with the 'megahertz wars' firmly over, both Intel and AMD are encouraging programmers to develop more multithreaded applications, so dual-core CPUs such as the 840 will perform faster over time. The trouble is that for the last 25 years, programmers have been used to writing single-threaded applications, and the mental shift required to programme multithreaded applications is extremely complex. Part of the problem is that the human brain can only consciously think about one thing at a time, so getting programmers to write applications that perform more than one task at a time is asking them to think in a way that's quite unnatural.
In multithreaded applications such as TMPGEnc, which we use for our video encoding benchmark, the 840 performed incredibly well, achieving a score of 2.92. In comparison, a 3.2GHz Pentium 4e scored just 1.58, while a dual 3.2GHz Xeon system scored 2.77. Most professional-level 3D applications are also multithreaded, and in Cinebench 2003, the 840 returned a very fast score of 611, while the dual Xeon scored exactly the same. The 3.2GHz Pentium 4e lagged way behind with a score of just 381. We also rendered two complex 3D scenes using NewTek LightWave 3D 7.5c and Discreet 3D Studio Max 7. In both tests, the 840 and dual-Xeon systems performed almost identically, taking just over eight minutes respectively to complete the LightWave render, and 1 minute, 16 seconds each to complete the 3D Studio Max test.
Although synthetic benchmarks such as SiSoftware Sandra 2005 don't really tell you how fast real applications will run, they allow you to easily compare one processor with another. Once again, in the CPU Arithmetic and CPU Multi-Media Benchmark, the 840 and dual-Xeon systems performed near identically. The only real noticeable difference was in the Memory Bandwidth test, in which the 840 pulled ahead with a score of 14,186MB/sec compared to 12,038MB/sec. The difference is most likely due to the 840's more modern chipset and PC2-5400 memory, while the dual-Xeon system ran on slower PC3200 DDR.
Another way to examine the performance benefits of a dual-core CPU such as the 840 is during multitasking. To simulate this, we tried a CPU-intensive task (ripping an audio CD) while playing Doom 3. As Windows XP is able to switch each process to a different core, there was absolutely no slowdown in Doom 3 - the average frame rate of 67.1fps is very smooth, and it also never dropped below 25fps.
We can also happily report that, like a dual-Xeon system, the 840 can handle running four instances of Folding@home 24 hours a day. We left our test PC folding non-stop for several days, and it remained rock-solid, although the toasty temperature of the HSF means you'll probably be able to switch off your central heating completely.
OVERCLOCKING
While Intel processors have traditionally overclocked further than their AMD counterparts, the Athlon 64 and Athlon 64 FX have one big advantage over Pentium 4e: an unlocked multiplier. On an Athlon 64, the multiplier can only be lowered, but on an Athlon 64 FX, it can also be raised, so with a good motherboard and great cooling, you can achieve some truly stellar overclocks. Other than Pentium M and Xeon, Intel locks the multiplier on its current CPUs, so it came as something of a surprise to us (actually, it was more of a bombshell) that the 840 is also fully unlocked. That's right, after years of banging on at Intel to sell an unlocked chip, even if it was just for us enthusiasts, we finally have one.
So how do you fancy having an air-cooled processor with two cores inside, each running at 4GHz? That's right, by swapping the Intel HSF for our CPC award-winning Arctic Cooling Freezer 7 HSF, raising the core voltage from 1.4V to 1.45V and upping the multiplier from 16 to 20, the 840 was more than happy to benchmark at 4GHz - that's an overclock of 800MHz on each core!
As you'd expect, performance in single-threaded applications at 4GHz was pretty spectacular; it averaged 71.1fps in Doom 3 and managed a Paint Shop Pro image editing score of 1.59, both of which are up there with high-end Athlon 64 systems.
However, with both cores running at 4GHz, it was multithreaded applications that provided the more serious challenge. The video encoding score of 3.40 is the fastest we've seen - even quicker than some of the volt-modded dual-Xeon systems we've been experimenting with for BTO in the CPC labs for the last few months.
The fact that we achieved this overclock using a typical HSF, with only a moderate voltage increase, is all the more impressive. On a motherboard more suited to overclocking, and with a water-cooling or phase-change cooling system, we're convinced the 840 could run faster still. After all, we got it to POST at 4.2GHz, although it wouldn't run Windows stably at this frequency. Even a battle-hardened dual-Xeon fanatic such as myself can see the huge potential in overclocking an 840, and that's without even upping the FSB. However, no matter which method you to use to overclock the 840, it's likely to mercilessly pummel even the fastest dual-Xeon or Athlon 64 FX systems into the ground.
CONCLUSION
Obviously, Intel is hoping that a Pentium Extreme Edition 840 will be a very attractive purchase for many enthusiasts and, for the first time in nearly 18 months (since the Northwood core Pentium 4c), we agree. If you're fed-up with applications crawling to a halt every time you try to run another task then a dual-core processor such as the 840 is the ideal solution. For those of you who have never owned or used a dual-processor system, it will completely change how you use your PC, as you're no longer limited to doing one thing at a time. You no longer have to close down other applications when you want to play a game - simply leave them up and running in the background, and let the second core take the strain.
For ultimate performance junkies, the 840 is the fastest CPU that money can buy. With PC2-5400 DDR2 memory support and a fully unlocked multiplier, the possibilities are near endless. What's more, there doesn't appear to be any performance hit from running two cores in a single CPU, as opposed to two CPUs on a dual-processor motherboard, so until dual-core Xeons make an appearance next year, an 840 is the way to go. In terms of pricing, an 840 is expected to sell for about the same amount as a Pentium 4 Extreme Edition at launch. This means that it will be a lot more expensive than two 3.2GHz Xeons, but given the fully unlocked multiplier we think the higher price is justified. And for those who don't have massive wads of cash lying around, the Pentium D could be a tempting alternative, although we'll have to wait and see how it compares.
With the 'megahertz wars' over, the 840 officially begins what's likely to become the 'multicore wars'. AMD also plans to launch dual-core Opterons and Athlon 64s in the near future, while Intel has another 13 multicore projects planned, and that's just the projects the company has publicly admitted to. In addition to the 840 and Pentium D, you can expect to see their replacement, the dual-core 'Presler', in the first half of 2006, the dual-core Xeon 'Dempsey' in the first quarter of 2006 and 'Yonah', a dual-core Pentium M-based CPU, some time in late 2005 or early 2006.
Dual-core processors such as the Pentium Extreme Edition 840 are just the beginning of a whole new cycle of CPU development, with four, eight and even more cores being integrated into a single CPU.
The only snag is that most current software isn't designed to take advantage of multiple cores, although support will get much stronger. Even taking this into account, though, the 840 is still an incredibly powerful CPU and, arguably, the perfect chip for power-hungry enthusiasts.
