Simviation Forums

Hey  Guys and Ladies,     Am doing a lot of study about the parts of a PC.  Just might  put one together or have it done to make sure all the parts are compatiable.   I seem to just "can't get it" concerning the  Front Side Bus  [FSB] and it's speed.    What is it for /  it's importance/ and why the speed ?   I do understand it can be a bottleneck - - - -  but how/why ?      My books don't answer these questions, - - - -  like it's really not that important  [ I know better than that ].       Appreciate your help.                caveman

The FSB can be compared to a city transport system.

All the traffic (including the buses) needs to efficiently move around the city as smoothly as possible with no traffic jams.

The roads are better if they are fast and wide as we all know so well.

The faster and wider the Front Side Bus, the more efficiently the data in your pc can be moved from one location to another.

Bus architecture is dependant on chipset. Chipsets are developed and sold to mainboard manufacturers who implement that technology in various ways.

At a basic level, the chipset will determine the potential front side bus speed for any given mainboard.

FSB speed isn't everything in a PC, but it's a darn good start.

Some modern 64 bit systems can deliver incredible data flow on the FSB which is theoretically 64 lanes wide and can transmit 2000 mhz speeds. An nForce4 chipset is typical of this type of system. Data processing of 6 gigabytes per second or more is typical on these modern rigs.

The definition of FSB speed is somewhat blurred in the new systems because of complex advances recently made. The speeds are derived as a function of several variables and are not made from a simple calculation as in the past.

Thank You very much.  You sure know how to explain this [FSB] in terms clearly understood.   As I look at what is available - - - it seems 800mhz is the  "standard" for a fast system.   I've seen only one type faster.   Am I correct in thinking that a PC should be assembled around this speed ?  [where am I going wrong in my understanding   ? ]     caveman  

Ok I think your thinking too deep concerning the initial build of a computer but thats good, really you need to decide what CPU you want first because the fsb is a "bus" it trasports. It is a major backbone to a computer but as I will tell you modern fsb's are really so fast you don't need to worry much about them yet.

A FSB of 800MHz applies to the Intel chipsets. It's actually 200MHz x 4, quad-pumped, in Intel's case. 4 lanes running at 200Mhz each. When adjusting FSB in the BIOS, it always refers to the speed of each lane. Default of 200, overclocked to 210, 215, etc.

For older AMD XP CPUS, they have a FSB of 400MHz, or 200MHz x 2, dual-pumped. Or 333Mhz FSB (166.6Mhz x 2).

Older Intel CPUs with a FSB of 533Mhz is actually 133.3Mhz x 4. And so on and so on.

The FSB is basically the connection speed between the CPU and Northbridge chip. The Northbridge chip houses the RAM controller, which controls the data transfer between CPU and RAM. RAM bandwidth and latencies are limited to the efficiency/speed of the RAM controller.

AMD64 CPUs do not use a FSB in the traditional sense, AMD64 instead uses HyperTransporT (HTT), which has the RAM/CPU interface directly on the CPU die, instead of the Northbridge die, resulting in more efficient transfer of data between RAM and CPU since it bypasses the Northbridge controller. It still uses the FSB for the CPU/Northbridge interface, but CPU/RAM interface is dictated by HTT. It operates at 800Mhz to 1000Mhz (200FSB x 4 or 200FSB x 5).

Hope this somewhat makes sense.

The keyword you need to be thinking about is "platform".

What platform do you want to run from, an Intel based rig or a an AMD based rig.

Quite different chipsets and hence bus architecture is used in each platform.

Once you chose a platform based on needs and advantages, you can look to a chipset. The most modern choice is often, but not always, the best.

Chipset selection invariably takes into account FSB speeds, the higher the better, and in recent systems, this will determine the CPU socket type as well. CPU sockets change when major advances occur so that older and incompatible CPU's can't be fitted to the more modern system.

A result of this would see me recommending a socket 939 based system for example. This would mean that the compatible system built around the 939 pin socket type should have all the goodies and expansion capabilities that one would expect from a top rate PC.

Hey Guys,   I'm still here        I've  copied and studied this info soooooo careful.        You "GUYS" need to write a book to explain "things" so the rest of us can understand it .   I "got it" much clearer than the many books I've read about building a PC.    I know I'm somewhat backward - - BUT  - - it is nice to understand things from the "BASIC's".    Thanks again.       caveman