Enhanced Intel SpeedStep Technology
Enhanced Intel SpeedStep technology allows the system to dynamically adjust processor voltage and core frequency, which can result in decreased average power consumption and decreased average heat production. By decreasing power and heat on Desktop PCs, system builders can (depending on system configurations) potentially lower acoustics, and even develop more innovative small form factor designs. Additionally, this feature can help address power concerns in companies with sites approaching the limits of bounded electrical infrastructures. Combined with existing power saving features, Enhanced Intel SpeedStep technology can provide an excellent balance between providing power when you need it and conserving it when you don’t.

Execute Disable Bit
Malicious buffer overflow attacks pose a significant security threat to businesses, increasing IT resource demands, and in some cases destroying digital assets. In a typical attack, a malicious worm creates a flood of code that overwhelms the processor, allowing the worm to propagate itself to the network, and other computers. Intel's Execute Disable Bit functionality, first released for the Intel?Itanium?processor family in 2001, can prevent certain classes of malicious "buffer overflow" attacks when combined with a supporting operating system. Execute Disable Bit allows the processor to classify areas in memory by where application code can execute and where it cannot. When a malicious worm attempts to insert code in the buffer, the processor disables code execution, preventing damage or worm propagation.

Execute Disable Bit currently requires one of the following operating systems to support it:

• Microsoft Windows Server 2003 x64 Edition
• Microsoft Windows Server 2003 with Service Pack 1
• Microsoft Windows XP Professsional x64
• Microsoft Windows XP with Service Pack 2
• SUSE Linux 9.2 
• Red Hat Enterprise Linux 3 Update 3

Of course, that’s just the relatively new technologies (although most were seen in the Intel 660 as well). Below are some of the original technologies that were introduced last year.

Advanced Dynamic Execution
The Advance Dynamic Execution engine is a very deep, out-of-order speculative execution engine that keeps the execution units executing instructions. It also includes an enhanced branch prediction algorithm that has the net effect of reducing the number of branch mis-predictions.

Streaming SIMD Extensions 3 (SSE3) Instructions
With the introduction of SSE2, the Intel NetBurst microarchitecture extended the SIMD capabilities that Intel MMX technology and SSE technology delivered by adding 144 instructions. The next generation 90 nm process-based Pentium 4 processor introduces the Streaming SIMD Extensions 3 (SSE3), which includes 13 additional SIMD instructions over SSE2. The 13 new instructions in SSE3 are primarily designed to improve thread synchronization and specific application areas such as media and gaming.

Hyper-Threading Technology
Hyper-Threading Technology (HT Technology) is ground-breaking technology that changes the landscape of processor design by going beyond GHz to improve processor performance. It allows software programs to "see" two processors and work more efficiently. This new technology enables the processor to execute two series, or threads, of instructions at the same time, thereby improving performance and system responsiveness. The Pentium 4 processor supporting HT Technology is designed specially to deliver immediate increases in performance and system responsiveness with existing applications in multitasking environments (that is, where two or more functions are running at the same time) and with many stand-alone applications today. Furthermore, the Pentium 4 processor supporting HT Technology provides performance headroom for the future.

Hyper-Pipelined Technology
The hyper-pipelined technology of the Intel NetBurst microarchitecture increases the pipeline depth delivering increased performance, frequency, and scalability of the processor. One of the key pipelines, the branch prediction/recovery pipeline, is implemented in 31 stages on the 90 nm Pentium 4 processor, compared to 20 stages on the 0.13 micron Pentium 4 processor.
 
Level 1 Execution Trace Cache
The 90 nm Pentium 4 processor features 16-KB data cache compared to 8-KB on the 0.13 micron Pentium 4 processor. In addition to the data cache, the Pentium 4 processor includes an Execution Trace Cache that stores up to 12-K decoded micro-ops in the order of program execution. This increases performance by removing the decoder from the main execution loop and makes more efficient usage of the cache storage space since instructions that are branched around are not stored. The result is a means to deliver a high volume of instructions to the processor's execution units and a reduction in the overall time required to recover from branches that have been mis-predicted.

Side-by-Side Comparison
It is always fairly interesting to see how one processor stacks up against another. Here I have put together a simple table to show how the 840 compares to the 3.73GHz XE and the 660.

Intel 840 Intel 3.73 XE Intel 660 Manufacturing Process 90nm 90nm 90nm Number of Execution Cores 2 1 1 Socket LGA775 LGA775 LGA775 Bus Speed 800MHz 1066MHz 800MHz L1 Cache 16KB 16KB 16KB L1 Trace Cache 12-k micro-ops 12-k micro-ops 12-k micro-ops L2 Cache 2 x 1MB (1MB per core) 2MB 2MB L3 Cache N/A N/A N/A EM64T Yes Yes Yes Intel SpeedStep Yes No Yes SSE3 Instruction Set Yes Yes Yes Execute Disable Bit Yes Yes Yes

The largest differences between the new Extreme Edition processor (the 840) and the older one are the bus speed and the number of execution cores. Other than those two things, the only other difference is the implementation of Intel’s SpeedStep technology in the 840. In essence, the 840 is a 660 with two execution cores instead of one.