Last month we gave you a preview of Intel's 6xx series of processors, including their new Pentium 4 Extreme Edition 3.73GHz. While we didn't see any new motherboard technologies, we saw a host of new features introduced into their processor lineup. We won't go into great detail about the new features, as that has been covered earlier, but here's a quick recap:

Features for 6xx and Extreme Edition

· Intel Extended Memory 64 Technology: The new processors feature Intel's Extended Memory 64 Technology (EM64T), which is not much unlike AMD's solution. There are two potential benefits to EM64T, provided you have the OS and software in place; a faster computer and more addressable memory.

Computing instructions are done in binary format (zero and one), and for 32-bit environments, each bit is capable of one binary instruction each clock cycle. Therefore, for previous Intel desktop processors, for each clock cycle, they were capable of 32 binary instructions. A 64-bit processor doubles that, so provided the environment is optimized for 64-bit computing, PCs should be much faster.

One of the greatest limitations of 32-bit processors is that they are only capable of addressing up to 4 GB of memory. In theory, a 64-bit CPU can process up to 16 exabytes of ram.

· Execute Disable Bit: The 6xx series will be the second group of Intel desktop processors to support Execute Disable Bit (XD Bit). XD Bit isn't really new for Intel, as it was implemented for the Itanium processor in 2001 and the Intel Pentium 4 570J last year. Note that all E0 step processors (denoted by the "J") support XD Bit.

How XD Bit works is certain memory pages are protected from buffer-overflow attacks. For most Intel desktop CPUs, the x86 architecture have no means of protection to malicious code writing themselves to these memory pages and executing. By enabling this in the BIOS and OS now, you can effectively shut the door on the code from taking over these memory pages.

· 1066FSB (Extreme Edition Only): Introduced with the Extreme Edition 3.46, the 1066FSB carries over to the 3.73GHz Extreme Edition. Note that only the 925XE chipset (as well as upcoming offerings from VIA, ATI and NVIDIA) officially support the faster FSB.

· More Cache: Both series of processors have 2MB of L2 cache. For the Extreme Edition, this is four times the value of the 3.46EE. Compared to the 5xx series, the 6xx will double the amount of cache. Of course, one of the concerns of doubling more cache is increasing the latencies as the larger the cache, the more time it takes to find the information. We used to gauge the clock cycles, and came with the following results:

Processor	L2 Cache Latency
Pentium 4 XE 3.73GHz	27 Cycles
Pentium 4 560	23 Cycles

We see a difference of 4 clock cycles, and clock speeds being equal, this works out to about a 17% increase in latency from the 5xx series. Based on some reviews comparing the 6xx and 5xx (we could not since we only received an Extreme Edition), in general there is an improvement in performance for applications, but less so for games. The main impact comes in workstation and server apps, so for home users, unless the application hits the memory threads often, there may not be much improvement at this time.

· More Transistors: The processors are still based on the 90nm Prescott core, but the transistor count will be bumped up to about 169 million. Their last group of Prescott processors were in the 125 million range. If you're worried about more heat, it shouldn't be much of an issue (at least when compared against the 5xx) as the die size has only increased slightly.

· Hyper-Threading Technology: While not new to the platform, this feature allows multithreaded software applications to execute threads in parallel. For this to work, you need a multithreaded OS (Windows NT and up) and application.

The last feature that Intel introduced was Enhanced SpeedStep (EIST). How EIST works is it saves power by intelligently throttling clock frequencies. The end result is lower power consumption, and less heat. Unfortunently, this is a feature unavailable for the Extreme Edition. Given the target market of the 3.73GHz EE, this is not really a surprise.

Here is a table that sums up how the CPUs fare against one another:

Processor	Frequency	Bus	L2	XD Bit	EM64T	EIST	Chipset	Price
Pentium 4 XE 3.73GHz	3.73GHz	1066	2MB	Yes	Yes	No	925XE
Pentium 4 660	3.60GHz	800	2MB	Yes	Yes	Yes	915/925
Pentium 4 650	3.40GHz	800	2MB	Yes	Yes	Yes	915/925
Pentium 4 640	3.20GHz	800	2MB	Yes	Yes	Yes	915/925
Pentium 4 630	3.00GHz	800	2MB	Yes	Yes	Yes	915/925
Pentium 4 XE 3.46GHz	3.46GHz	1066	512KB	No	No	No	925XE
Pentium 4 560J	3.60GHz	800	1MB	Yes	No	No	915/925

The Intel Pentium 4 3.73GHz Extreme Edition

As introduced with the 5xx series, the 6xx and 3.73GHz Extreme Edition are based on the Land Grid Array 775 (LGA775, AKA Socket-T), and has no pins as those are found on the motherboard now. Along with the processor, we received Intel's stock heatsink. It is a similar heatsink to those provided with their 5xx series of CPUs and features aluminum fins surrounding a copper core. The fan itself is rated for a maximum of 5000rpm, which can get quite noisy, but when the CPU is idle or under light load, it slows down to very acceptable noise levels.

As with the Pentium 4 XE 3.46GHz, motherboard support is restricted to the 925XE chipset in the case of Intel chipsets. We can confirm that the PT Series of chipsets from VIA do support the 3.73GHz Extreme Edition, and unless something changes in the near future, NVIDIA's nForce for the Pentium 4, and the ATI Radeon XPRESS 200 will support the CPU as well. Future Intel motherboard support is still unknown, but it's likely the Lakeport (mainstream) and Glenwood (enthusiast) chipsets coming next quarter will support the processor.

Test Setup

ABIT Fatal1ty AA8XE: Intel P4 XE 3.73GHz, 2 x 512MB Corsair TWINX PC5400 Pro, ATI X850XT-PE, 160GB Seagate SATA 7200.7, Windows XP SP1, ATI Catalyst 5.3.

ABIT Fatal1ty AA8XE: Intel P4 560, 2 x 512MB Corsair TWINX PC5400 Pro, ATI X850XT-PE, 160GB Seagate SATA 7200.7, Windows XP SP1, ATI Catalyst 5.3.

Soltek SL-K890Pro-939: Athlon FX-55, 2 x 512MB Corsair TWINX PC3200XL, ATI X850XT-PE, 160GB Seagate 7200.7, Windows XP SP1, ATI Catalyst 5.3, VIA Hyperion 4.55.

Going up the 3.73GHz Extreme Edition will be the Pentium 4 560, and the Athlon FX-55. Outside of the CPUs, memory and obviously the motherboards, all the setups share similar peripheral components. Onboard audio was enabled in the BIOS for all the boards, but not used during game testing.

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