NetBurst Micro Architecture
Intel's name for the Pentium 4's new design is "NetBurst". Like with the Intel Pentium III and its SSE instructions to supposedly make internet content load quicker, Intel is trying its hardest to push the idea that Intel's new processor will make your web pages load quicker. Unfortunately, Internet is mostly limited to your modem's maximum speed and the speed of your ISP. The average consumer, however, is not going to know this straight off and it is a perfect way to market the Pentium 4.
Another big issue with the Pentium 4's "NetBurst Micro Architecture" is its obvious focus to deliver the highest clock rates. Again, 'NetBurst' shows its roots in Intel's marketing department. While Intel in the past has said "MHz isn't everything", it seems that Intel is trying to ring that bell that they tried to cut down in the days of the Cyrix 6x86 CPU's. As many of you may know by now, the Intel Pentium 4 at the same clock speed can't beat an AMD Athlon in just about every benchmark today. While these benchmark programs aren't SSE2 optimized (yet), it does show that Intel is trying to focus more on the future and not on the present. This could be a very big marketing mistake with most of the hardware community staying away from expensive Pentium 4/RDRAM solutions at the moment. However, if you are one of the hardware junkies like myself who have to have the fastest thing with the highest number on it, Intel has taken this crown.
Pentium 4's gets a new Bus.
For most of the past 3 years, Intel have been relying on the P6 bus used by the current P3 and Celeron range. While this bus has been easy to overclock and very stable, it doesn't have the scalability that is required for future processors. Intel has finally decided to step away from the P6 and introduce the new P4 400MHz QDR FSB.
The well-known 'FSB' of Pentium 3 is clocked at 133 MHz and able to transfer 64-bit of data per clock, offering a data bandwidth of 8 byte * 133 million/s = 1,066 MB/s. Pentium 4's system bus is only clocked at 100 MHz and also 64-bit wide, but it is "quad data rate", using the same principle as AGP4x. The new bus can transfer 8 byte x 100 million/s x 4 = 3,200 MB/s. This is obviously a tremendous improvement that even leaves AMD's EV6-bus far behind. The bus of the most recent Athlon's is clocked at 133 MHz, 64-bit wide and "double data rate", offering 8 byte x 133 million/s x 2 = 2,133 MB/s. Intel's Pentium 4 CPU is paired with the i850 chipset, a Dual Channel RDRAM solution. The i850 has two independent RDRAM channels which can deliver up to 3.2GB/s max memory bandwidth when used with four RIMM modules.
Like its predecessor, the Intel Pentium 4 is equipped with 256Kbyte of Advanced Transfer Cache, or ATC as it is known, running at the same speed of the CPU core. For example, on the Intel Pentium 4 2.0GHz we have here, the ATC is 256Kbyte and runs at 2000MHz or 2.0GHz. That is fast for cache; really fast. While the L2 cache hasn't grown over the Pentium III processor, the L1 cache of the Pentium 4 has actually shrunk. The Pentium III was equipped with 16Kbyte or Data and 12Kbyte or Instruction cache to make a total of 32Kbyte of L2 cache. Intel has dropped the Data cache on the Pentium 4 to 8Kbyte. That is remarkably small, but they have also added a new feature to the L1 cache; "Execution Trace Cache".
Rapid Execution Engine
Another feature of the Pentium 4 which is unique to Intel is the Rapid Execution Engine, or REE for short. The REE works on the principal of two double pumped ALU's and two double pumped AGU's. This allows for the engine to process 2x the amount of a P3 or Athlon CPU.
The story looks a lot different for the instructions that cannot be processed by the rapid execution units. Those instructions, or µOPs, need to use the one and only slow ALU's which is not double pumped. The majority of instructions need to use this path, which obviously sounds scary. However, the majority of code is in actual fact consisting of the most simple 'AND', 'OR', 'XOR', 'ADD', instructions, making Intel's "Rapid Execution Engine" design sensible though not particularly amazing.
Connection, Die and other Goodies
Intel's Pentium 4 Processor is available in two packages; Socket 423 and Socket 478. Intel plans to phase out the 423 pin socket over the new 3-4 months to make way for the mPGA Willamette and Northwood core Pentium 4 CPU's. While the 478 pin Pentium 4 may sound like it would be a larger CPU, it is actually smaller; about 1/3 the size of a 423 Pentium 4. mPGA pins are about the size of a pin head and spaced less than 1mm apart.
From the picture below you can see the 423 pin P4 on the left and the 478 pin P4 on the right.
The difference in size is amazing.
The die size of the Pentium 4 is unchanged from the Pentium 3, using the same 0.18 micron process the current 423 and 478 P4's. Intel has added another new feature to the Pentium 4; the heat slug.
When the Coppermine Pentium 3 was released, there was some major concerns about the very small area of CPU making contact with the heatsink. If the heatsink was poorly installed then, the CPU could be permanently damaged or totally destroyed by being crushed. Intel added a large heat slug to the Pentium 4 to increase thermal contact and prevent the core from being crushed by heatsinks.