CPU speed blitz


The upper end of the CPU market received a major jolt this month. Firstly, AMD re­-leased faster ver­sions of its Athlon 64 and Athlon 64 FX processor products (Athlon 64 4000+ and Athlon 64 FX-55). Meanwhile, Intel announced a new motherboard chipset - the 925XE Express - to go with its new Pentium 4 Extreme Edition 3.46GHz CPU.

Ultimate performance

Intel's Pentium 4 Extreme Edition pro­cessor (P4 EE) is aimed at the very high end of the consumer market for users who want ultimate performance for serious gaming and multimedia production applications. The latest chip features an LGA775 processor package and has a clock speed of 3.46GHz. It is built using the older 0.13-micron technology, as opposed to 0.09-micron, which is used in the current regular Pentium 4 range.

The P4 EE has always been a perfor­mance step ahead of the regular Pentium 4 chips due to the total amount of cache memory. A regular Pentium 4 has a 1MB level 2 cache, while the P4 EE has a 512KB level 2 cache as well as a 2MB level 3 cache. Cache memory is accessible to the CPU much quicker than regular system memory due to it being integrated on the CPU die itself and it is usually a place where frequently used data is stored. In addition to the level 3 cache, the latest P4 EE also differentiates itself from regular Pentium 4 chips with its improved front-side bus speed. It incorporates a quad-pumped 266MHz front-side bus speed of 1066MHz (4x266MHz), as opposed to the 800MHz (4x200MHz) of the regular Pentium 4 chips.

The front-side bus is the data pathway between the main memory and the CPU and this increase in speed is enabled by the new 925XE Express chipset.

This chipset features a new memory controller that has native support for 533MHz DDR2 memory modules (2x266MHz), and this controller also supports lower memory CAS latency times. Put simply, CAS latency is the time it takes to locate a particular memory address (column and row) for data that needs to be accessed. The 925XE Express supports memory modules with a CAS latency rating as low as CL3. We did not have this type of memory available to us at the time of testing, so our test results are with a CAS latency rating of CL4.

The 925XE Express chipset also features one PCI Express x16 graphics slot along with multiple PCI Express x1 expansion slots and works in conjunction with the ICH6R input/output controller hub to provide Serial ATA RAID and high definition audio support. We tested it with 1GB of DDR2 533MHz memory, a Radeon X800 PCI Express graphics adapter and 2x120GB Seagate hard drives set up in a RAID 0 array.

No more special FX?

Like the P4 EE, AMD's FX range of Athlon 64 CPUs is strictly for the performance enthusiast. The latest Athlon 64 FX-55 is in direct competition with the P4 EE 3.46GHz, and boasts the current highest clock speed of any Athlon 64 processor: 2.6GHz. The Athlon 64 4000+ CPU has a slightly slower clock speed of 2.4GHz, but is essentially the same chip technology as the Athlon FX 64-55. This begs the questions: will AMD persist with the FX naming convention in the future? And, what will be the difference between future FX chips and regular Athlon 64 chips?

Indeed, the only noticeable difference between these two Athlon chips is their clock speed. Both feature a 939-pin interface; both are built using the 0.13-micron process; both have an integrated 128-bit memory controller that supports dual-channel memory configurations; both have a 1MB level 2 cache and both support a 2GHz HyperTransport link. HyperTransport is the interconnection between the CPU and the main system chipset.

For testing, we used the Plus Corporation Aspect A50 (Athlon 64 4000+) and the plus Corporation Altera FX-55A (Athlon 64 FX-55). Please refer to the Best Buys on page 69 for the specification details of both these tested systems.

How they compare

We used PC WorldBench 5 to compare the speeds of these chips in workloads encompassing office applications, de­-sign, music and video encoding as well as multitasking. The Athlon FX-55, with its 2.6GHz clock speed, is the clear winner here. It posted a score that is 10 per cent faster than the baseline system score of 100 for this benchmark.

The almost identical Athlon 64 4000+, with its 2.4GHz clock speed, posted a score that is 8 per cent faster than the baseline, while the P4 EE 3.46GHz chip posted a score that is 1 per cent slower than the baseline for this benchmark.

The P4 EE 3.4GHz chip, with its PCI Express platform, has a clear advantage in 3DMark 2005, which is based on DirectX 9.0 tests, but the Unreal Tournament frame rate scores are well matched between all the CPUs.

In terms of heat generation, the P4 EE 3.46GHz chip has a thermal power dissipation rating of 110 watts, while the Athlon 64 FX-55 is rated at 104 watts and the Athlon 64 4000+ at 89 watts.

High-end CPUs need high-end graphics

Although the new 925XE Express chipset has one major improvement over the 925X Express chipset in its design, which is its support for a faster 1066MHz front-side bus speed, we couldn't help but notice the lack of a second PCI Express 16x graphics slot.

A second slot is needed if you want to make use of the Scalable Link Interface (SLI) technology in the latest NVIDIA graphics cards - and let's face it, if you are an enthusiast thinking of purchasing an Extreme Edition CPU, you will most likely want to install the best available graphics solution.

SLI technology has been developed by NVIDIA to allow two graphics cards to be installed in the same system, which can then be connected together to effectively double the processing power of your graphics sub-system. This enables pretty much all games to be run at their maximum detail settings, assuming you have high-end cards installed.

There is no word yet on when Intel will introduce an SLI-capable chipset into its consumer line of products, but an announcement for the AMD platform has already been made by NVIDIA. Its nForce 4 SLI MCP chipset will have support for two PCI Express x16 graphics slots. Other variations of this chipset, nForce 4 MCP and nForce 4 Ultra MCP will have support for one PCI Express x16 slot, as will VIA's K8T890 chipset.

At the moment, if you want to buy or build yourself a really high-end machine, then it is probably worth waiting a little while until SLI capable motherboards for AMD Athlon 64 chips become available. NVIDIA is working on certification and logo programs with their partners to ensure that retail products which can take advantage of SLI are marked clearly.

In brief:

If you're after the best overall application performance for your system, then either of the Athlon 64 chips will do, but if you're after blazing gaming performance, then the P4 EE 3.46GHz chip has a slight advantage. We impatiently await PCI Express chipsets for the AMD platform so we can accurately test gaming performance with these high-end chips.

Intel Pentium 4 Extreme Edition 3.46GHz
Three and a half stars out of five Price: $1469 approx. URL: www.intel.com.au

AMD Athlon FX 64-55
Three and a half stars out of five Price: $1412 approx. URL: www.amd.com

AMD Athlon 64 4000+
Four and a half stars out of five Price: $1086 approx. URL: www.amd.com

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Elias Plastiras
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