The Pentium 4 64-bit Architecture
When it comes down to the finer points of the Pentium 4 64-bit series, the fundamental core is based directly on the Prescott architecture with the latest core revisions that Intel has started to offer.
Packaging wise (now I am not talking about the box here) Intel has chosen to produce the 6xx and the 64-bit Extreme Edition (refereed to now on as the EE64) series in Socket T (Socket 775 as its otherwise known) so users of the MPGA-478 CPU won't see this baby coming to boards near them, however, the design is that the chip still uses the 800MHz FSB, so usage on the Socket T I875 and I865PE boards is certainly an option however motherboard vendors updating their BIOS's to support the additional features is another thing.
SSE3 also makes its return to the 6xx series, showing that Intel is pushing for SSE3 to take over where SSE2 left off. Applications are now starting to take advantage of this technology, with updates coming out for mode audio and video encoders to take advantage of the extra 13 stages to the SSE architecture; it should start to see its way into DX9.1 supporting games when they start to arrive.
XD Bit Permanent
One of the new features that Intel has added to the Pentium 4 6xx is the XD or Execution Disable bit. While available on only a few of the 5xx series models, this new bit has been available to AMD Athlon 64 users with Windows XP SP2 installed.
This new addition allows the CPU to permanently disable malicious programs that use a certain execution bit that allows viruses and other nasties to infect your PC. While it's not a replacement for a virus scanner, it will see the removal of a bit of the spyware slowdowns that we have seen over the last year.
EM64T, 64-bit for the Intel masses
AMD's biggest claim with its Athlon 64 CPU was that it simply was the only CPU available to desktop uses with x86-64 or 64-bit instruction set but the only way to use it was to use a beta version of Windows XP 64-bit or swap to Linux (both unattractive for gamers). With Microsoft readying the 64-bit version of Windows XP, Intel has moved one of its server technologies into the desktop field, that being EM64T.
EM64T or Extended Memory 64 technology is what Intel calls its x86-64 instruction set rather than saying it supports AMD64 technology, which as you can imagine would give AMD all the ammunition it needs to shoot down Intel for more sales shares. AM64T allows the Pentium 4 to now support Windows XP 64-bit when its becomes available (probably Q3'05) as well as the ability to address memory above 4GB.
AMD's claim to fame of having the only 64-bit CPU has now vanished; at least they can say they had the first 64-bit CPU for the desktop. But that's not as good the saying the only 64-bit for the desktop.
EIST, Demand Based Switching (6xx only feature)
Over the last few months the hardware world has shown that the Mobile and the Desktop can be intertwined. Recently we have seen Pentium M motherboards for desktop computers make their way into the market. Pentium M makes a great quiet PC alternative due to its high performance and low power, the main reason is its Speedstep technology.
AMD added Cool'n'Quiet technology to its AMD Athlon 64 processor. This technology allows the CPU multiplier and voltage to be reduced to a pre-determined minimum when the CPU reaches idle state. Intel has built on its Speedstep technology with the Pentium 4 6xx series to allow a much deeper sleep state than that of the Pentium M processor in order to reduce the amount of heat that is generated as well as the mount of power consumed when the CPU is in an idle state. Intel also uses dynamic switching to allow the CPU to go in and out of the Speedstep state without the user even realising that the system is switching.
The bigger they are, the more they can store
When the Prescott core first arrived on the scene, we saw Intel double the caches. First off the L1 data cache increased from 8KB to 16KB. The L2 cache also doubled in size from 512MB of the Northwood core to 1 MB monster, which was to compete with the Socket 764 Athlon 64's 1MB L2 cache on the Claw hammer core.
The Pentium 4 6xx and EE64 series sees the L2 cache once again grow in size, and keeping with Intel's double cache, the L2 cache size is now 2MB; double that of the 5xx series. Since the latest blitz from both AMD and Intel is on the more than MHz philosophy, we are bound to see architecture changes and additions such as larger caches, extra cores and such, as going beyond the current 3.8GHz barrier is simply not possible with today's cooling and manufacturing processes.
One of the biggest changes to the P4EE64 is the major removal of one of the biggest selling points that distinguished it from the Northwood core, that being the Level 3 cache. The new Pentium 4 Extreme Edition has removed the L3 cache completely, moving the 2MB of cache on to the L2 cache - is this going to change anything in terms of speed? We will have to find out shortly.
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