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Intel 6xx Series Overview Intel 6xx Series Overview: We take a look at the technology and features of Intel's latest 6xx series of processors. Was it worth the wait?
Date: February 20, 2005
Written By:
Price: (P4 630)

It's been fairly quiet on the Intel front since the introduction of the 5xx series of processors last June. Since then, they introduced a new Extreme Edition CPU that brought the 1066MHz quad pumped bus to the Pentium 4 platform and a new 925XE chipset to go along with it. Truth be told, the new processor and chipset weren't really based on new technologies, but rather, they were simply existing Extreme Edition processors and Alderwood chipsets on steroids.

One reason for some of Intel's relative silence was because last year's 5xx, Alderwood and Grantsdale launch was so big. Several new technologies for the consumer desktop were introduced, notably DDR2, and PCI Express. Over at the AMD camp, nothing much has come out of them technology-wise either during this same time frame, and only recently with the VIA K8T890 and nForce 4 has AMD adopted the PCI Express interface. Unless AMD reworks their CPU infrastructure, DDR2 is still a whiles away, but nonetheless, one marketing point AMD has always held over Intel on the desktop is support for 64-bit computing.

That changes today as Intel will be introducing the 6xx series of processors. Hyper-Threading technology is still accounted for and will be present on all their 6xx chips, including the Extreme Edition. It will still be LGA775 based, and have a 90nm Prescott core. As you might think, on the surface, not much has changed, but digging a bit deeper reveals some technologies that were a long time coming.

Intel Extended Memory 64 Technology

While it's been there for Intel server and workstations (Itanium) since last year, let alone AMD CPUs since 2003, 64-bit computing for Intel desktop users has been a no show up until now. The 6xx series of processors will feature Intel's Extended Memory 64 Technology (EM64T) at long last.

Unlike the Itanium, which requires 64-bit applications and drivers (and run 32-bit code in emulation), the 6xx will not have the same limitations. The CPU will also be capable of running in native (legacy) mode, meaning, in a 32-bit environment, a 32-bit application will run as it should and not be hobbled by any emulation mode or something similar. In other words, the performance should be in line with their previous 5xx CPUs, clock speeds being equal, in non-64-bit apps.

Granted, unless you're a Linux user, a 64-bit processor won't do much good without a 64-bit Windows OS. Microsoft has been slow to release to market the final version (and it doesn't look like it will be a retail product, but rather it will be sent to OEMs only), but now with Intel joining the fray, it should hopefully speed up the final release of the OS.

Now, marketing hype aside, just like we asked when AMD released the Athlon 64/FX for the desktop, what exactly does 64-bit processors do for the end user provided they have the OS and software in place? In theory, a much faster computer. 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.

Another benefit is the increase in addressable memory. 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. While we're not going to see desktop systems armed with that much ram, it does open up options for board makers and users with deeper pockets.

Enhanced SpeedStep

SpeedStep will get an overhaul with the 6xx series. Similar to what can be found in their Centrino mobile technology, the (EIST) will be much more efficient at saving power by intelligently throttling clock frequencies. In the mobile world, SpeedStep only kicks in when the notebook goes into battery mode, but Enhanced SpeedStep is controlled by the OS and application and is either running in performance mode or battery optimized mode. For the 6xx series, EIST will work by reducing the bus ratio multiplier (thus the frequency) and adjusting the voltage accordingly.

EIST isn't the only way Intel is tackling power though, as it is only one part of their Enhanced Power Management initiative. Enhanced Halt State (C1E) is another method of reducing heat and is OS driven. C1E is very application and situation dependent, and can occur as frequently as in-between keystrokes. A typical Halt State (C1) will stop 90% of clocks, and run the remaining 10% at full speed. C1E, like EIST, lowers the bus multiplier and voltage to achieve more efficient results; that is, better power consumption with less of a hit to performance when compared to C1.

The last piece of the puzzle for Intel's Enhanced Power Management is Thermal Monitor 2 (TM2).

The previous Thermal Monitor (TM1) worked by lowering the clock speed by about 50% depending on the die temperature. Again, frequency and voltage are the subjects that are adjusted, and Intel's CPUs should run 40% cooler without as large a performance hit.

For desktop use, this may seem redundant as most of us will probably want full speed all the time. This is an option as it's something that can be enabled or disabled, but one benefit in theory would be longer lifetimes for CPUs as it will run cooler when less of a load is placed on it. When you think about it, you may not need the maximum speed when typing a Word document, but it will fire up the processor dynamically if you decide to load up something CPU intensive. Therefore, your CPU won't be running at 55°C at all times, and the end result is a CPU that runs cooler and longer.

Again, this may be a moot point as many enthusiasts change PCs more often than their socks, but for corporate consumers, the power savings and longer life cycles will be more attracted to this feature. There will also be cost savings in IT rooms where air conditioning is concerned. Many corporations use "blade" PCs, which are multiple PCs plugged into racks or cages. For the end user, their station has nothing more than a keyboard, mouse and monitor, as their computer may be locked up in a server room somewhere. In a 500 user environment, all those blades will generate a lot of hear, more so with the faster ones. With EIST, idle or low load blades will throttle down and as a result run cooler. This in turn reduces power consumption, as well as keeping the room's cooling at a reasonable temperature without turning the AC up.

In terms of support, EIST is supported in Windows XP SP2 and up. All of Intel's 6xx CPUs will support Enhanced Power Management, but will not be supported with the Extreme Edition CPU. Considering the enthusiast and workstation market of the Extreme Edition, this is not too much of a surprise.

More Cache

For the Extreme Edition and non-Extreme Edition 6xx CPUs, we're going to see 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. 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.

Execute Disable Bit

The 6xx series will be the second group of Intel desktop processors to support Execute Disable Bit (XD Bit). Introduced with the Intel Pentium 4 570J, all 6xx CPUs will have this feature available in the BIOS (and OS) and can be enabled or disabled if you wish.

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. I suppose the best analogy I can think of is a guy sells you a new storm door without a lock. The door will keep something's out, but it won't stop anybody who knows what they are doing (as simple as pushing the door open in this case) from getting in. The XD Bit is akin to the same guy now selling these doors with locks, which the owner can control by locking and unlocking. Difference here in terms of computing is you're better off keeping it locked.

We should point out that the XD Bit doesn't work like a FireWall or anti-spyware or virus scanner program and will not stop any malware from installing on your PC, but it will monitor the activity in these reserved memory pages and stop them from taking over your PC.

XD Bit isn't really new for Intel, as it was implemented for the Itanium processor in 2001, and AMD has a similar NX bit (Non-Execute) technology in their Athlon 64 and Opteron processors for over a year, but it is a step in the right direction for Intel given the problems we've had with trojans and worms the past several years.

Clock Speeds and Chipset Support

No doubt, this is what everyone is going to ask about first, so here's a table outlining what is being launched today:

Pentium 4 XE 3.73GHz
Pentium 4 660
Pentium 4 650
Pentium 4 640
Pentium 4 630

If you've guessed that the new Pentium 4 XE 3.73GHz will only work at its full potential with the 925XE chipset, you've guessed right. As it stands, all 6xx CPUs will run at 800FSB, and will work across their entire LGA775 platform (915G/P, 925X/XE). For now we won't be holding our breath for 1066FSB versions of the 6xx until the release of the Lakeport (mainstream) and Glenwood (enthusiast) chipsets next quarter, and even that is no guarantee. While we do not have pricing for the Pentium 4 XE 3.73GHz, our best guess is it will fall in line with previous Extreme Edition launch prices and come in at ~$999 in lots of a thousand.


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