What's Behind NetBurst?
Intel calls the new architecture of Pentium 4 'NetBurst'. The idea behind this name is for me just as unfathomable as the 'Internet SIMD Streaming Extension', as Intel liked to call Pentium 3's 'SSE' or 'ISSE'. Believe me, your web pages won't pop up any faster, downloads will take just as long and the Internet won't 'burst' either. However, Intel is trying its hardest to be trendy and since the Internet is still hip, it is a perfect vehicle to market Pentium 4. The name 'NetBurst' could also be a hint towards Pentium 4's performance characteristics. Professional PC-users might not care quite as much for an 'Internet-accelerating' processor, but more for a product that makes them get their work done as fast as possible. Looking at the benchmark results further down in this article shows that Pentium 4 shines a lot more at recreational software than in professional applications.
Another big issue with Pentium 4's 'NetBurst-Architecture' is its obvious focus to deliver highest clock rates. Again 'NetBurst' shows its roots in Intel's marketing department. The avid Tom's Hardware Guide reader will be aware of it, but the average computer user still hasn't grasped the fact that clock rate does NOT automatically translate in performance when looking at different processor designs. This is another issue targeted by Pentium 4 and 'NetBurst'. Intel wants clock rate at almost any cost and the Pentium 4 design is perfect to deliver exactly that. Average Joe is supposed to read those high Giga-Hertz numbers and conclude that this alone is already good enough to make Pentium 4 the fastest processor in the universe. Marketing - that's what the name 'NetBurst' seems to be all about.
NetBurst includes the following goodies that have been implemented into the new Pentium 4 desgin:
- Faster System Bus
- Advanced Transfer Cache (already known from Pentium III)
- Advanced Dynamic Execution (Execution Trace Cache, Enhanced Branch Prediction)
- Hyper Pipelined Technology
- Rapid Execution Engine
- Enhanced Floating Point and Multi-Media (SSE2)
Let's look at each of those features in more detail, acting like code/data that is being processed by Pentium 4.
The New Processor Bus
The first new feature seen by code or data as it enters Pentium 4 is the new system bus. 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-pumped', using the same principle as AGP4x. Thus it can transfer 8 Byte * 100 million/s * 4 = 3,200 MB/s. This is obviously a tremendous improvement that even leaves AMD's recently 'upgraded ' EV6-bus quite far behind. The bus of the most recent Athlon's is clocked at 133 MHz, 64 bit wide and 'double-pumped', offering 8 Byte * 133 million/s * 2 = 2,133 MB/s.
The new bus of Pentium 4 enables it to exchange data with the rest of the system faster than any other x86-processor, thus removing one important bottleneck that Pentium 3 was suffering from. However, the fastest processor bus doesn't help much unless the system's main memory can deliver data at an according pace. Intel's new 850 chipset for Pentium 4, which currently represents the only chipset for this new CPU, is using two Rambus channels and therefore the expensive and unpopular RDRAM. However, these two RDRAM channels are able to deliver the same data bandwidth as Pentium 4's new bus (3,200 MB/s), making them a perfect match at least on paper. This constellation enables Pentium 4-systems to have the highest data transfer rates between processor, system and main memory, which is a clear benefit. At the same time system cost is impacted by the high price of RDRAM plus the fact that a Pentium 4-system always requires two or even four RDRAM-RIMMs of the same size and spec. One, three or mixed RIMMs are not an option.