Menu
FSB800: first impression and a look into the future

FSB800: first impression and a look into the future

Bandwidth and memory

Before we turn to the test results, let's talk about the basics of the frontside bus and its connection to the Northbridge. The Northbridge, known as the Memory Controller Hub at Intel, is used by the processor to communicate with the main memory, among other things. The route between the processor and the northbridge is generally referred to as the frontside bus (FSB) or system bus. The main memory is connected to the northbridge via the memory bus. In both cases, the clock rate is decisive for the bandwidth. The larger the bandwidth, the more data can be transmitted.

Let's take a quick look at the bandwidth of the Pentium 4 FSB at the currently available and planned clock rates:

  • FSB400: 64 bit bus width * 100 MHz bus rate * 4 data packages/8 = 3200 MB/s
  • FSB533: 64 bit bus width * 133 MHz bus rate * 4 data packages/8 = 4200 MB/s
  • FSB800: 64 bit bus width * 200 MHz bus clock * 4 data packets/8 = 6400 MB/s

In the event of an emergency, the next year's Pentium 4 Processors shovel twice as much data to the Northbridge as the first Pentium 4 models . But the frontside bus is not everything, the connection of the main memory also plays an important role:

SingleChannel DDR SDRAM
  • DDR266: 64 bit bus width * 133 MHz bus clock * 2 data packets/8 = 2128 MB/s
  • DDR333: 64 bit bus width * 166 MHz bus clock * 2 Data packets/8 = 2666 MB/s
  • DDR400: 64 bit bus width * 200 MHz bus clock * 2 data packets/8 = 3200 MB/s Dual Channel DDR SDRAM
  • DDR266: 2x 64 bit Bus width * 133 MHz bus clock * 2 data packets/8 = 4256 MB/s
  • DDR333: 2x 64 bit bus width * 166 MHz bus clock * 2 data packets/8 = 5332 MB/s
  • DDR400 : 2x 64 bit bus width * 200 MHz bus clock * 2 data packets/8 = 6400 MB/s

Because Intel itself will not present a new Rambus chipset and is concentrating entirely on DDR SDRAM , we would like to do the same at this point. At first glance it becomes clear that only dual-channel memory, in which two memory modules are addressed in parallel by the memory controller, can satisfy the hunger for bandwidth of the current and future Pentium 4 processors. Suitable chipsets have been presented or are still pending.

[b] As the listing also shows, however DDR400 with its 3.2GB is not up to an FSB of 533MHz with 4.2GB and cannot supply our FSB800 with 6.4GB with enough data. In this respect, we only have a subtle look at the pure benefit of the faster connection to the Northbridge, if at all. The absolute increase in speed will only be achieved by boards that can shovel 6.4GB of data per second from the RAM.

The Granite Bay (7205) from Asus, the P4G8X Deluxe, which we had at our disposal, was unfortunately not closed to persuade stable operation with Dual Channel DDR SDRAM at 200 MHz (DDR400). Rather, the clock limit was reached with a front-side bus of 185 MHz and a resulting memory clock of 370 MHz. More on this in the section 'Granite Bay'. [/B]

On the next page: Mainboard andChipset