Front-side bus - Wikipedia
In older systems, the front-side bus (FSB) was synchronously tied to the still used an FSB now had a clock divider between itself and the memory controller. For DDR, we need a memory I/O clock (not memory speed, DDR3 . What is the difference between the External and the Internal clock rate. The FSB speed is the speed of the link between the processor and . best explanation of the relation between FSB and memory I've ever seen. I have been attempting to further understand the relationship between RAM speed and FSB. I was always taught that, where possible, you must.
Modern chipsets can run them independently without a significant performance hit. Chipsets support specific memory speeds.
memory - Front Side Bus and RAM speed - Super User
The main concern is that the memory speed should not bottleneck the performance of the system. With Intel-based processors, the processor has to talk to the memory through the chipset, where the memory controller resides. So there are two pipes, one between the processor and the memory controller hub chipset and the other between the memory controller hub and the RAM.
These are the FSB and memory buses respectively. As you might imagine, you'd want their bandwidth data rate to match.
What's the difference between FSB & Memory bus?
Each transfer is 64 bits. So you'd want a memory solution that can match or exceed this bandwidth, otherwise you are potentially creating a bottleneck with slow RAM.
As it happens, modern memory controllers can talk to two channels of memory, which means that if you pair up your memory modules, one in each of the pair of channels, your memory controller will be able to talk to two memory modules per transfer. Each transfer is 64 bits wide. This is also why it's called PC However, this doesn't mean you won't see a benefit in performance if you go for faster memory.
When a memory controller makes a request to memory, there are several cycles it has to wait "latency" before it can get data.
Relationship Between RAM speed and Front Side Bus
Note that these numbers don't depend on how much data you can shove through the pipes bandwidthbut rather the clock rate. The latency is a significant factor since the processor is doing nothing between the first request and the first response, and since memory access tends to be bursty, with lots of stops and starts, this adds up rather quickly.
If you're overclocking an Intel system, you are raising the FSB clock rate. This also increases the bandwidth the processor can use, so it helps to have faster RAM in this situation since the processor continues to be matched by the RAM in bandwidth. The Athlon 64 and Athlon 64 X2 processors are somewhat different in architecture.
In their case, the memory controller is integrated on to the processor itself, so there is no FSB that limits the bandwidth used -- the limit is the speed of memory that the processor itself supports. The AMD processors are a bit tricky when it comes to memory clock rates, however.
Due to differences in CPU and system architecture, overall system performance can vary in unexpected ways with different FSB-to-memory ratios. In imageaudiovideogamingFPGA synthesis and scientific applications that perform a small amount of work on each element of a large data setFSB speed becomes a major performance issue. However, if the computations involving each element are more complex, the processor will spend longer performing these; therefore, the FSB will be able to keep pace because the rate at which the memory is accessed is reduced.
In older systems, these buses are operated at a set fraction of the front-side bus frequency. This fraction was set by the BIOS. Overclocking Overclocking is the practice of making computer components operate beyond their stock performance levels by manipulating the frequencies at which the component is set to run, and, when necessary, modifying the voltage sent to the component to allow it to operate at these higher frequencies more stably.
Almost all CPU manufacturers now "lock" a preset multiplier setting into the chip.
- Front-side bus
- Relationship between FSB and RAM speed
- Important to match FSB and memory speed nowadays?
Some other processors from AMD and Intel are unlocked from the factory and labeled as an "enthusiast-grade" processors by end users and retailers because of this feature. For all processors, increasing the FSB speed can be done to boost processing speed by reducing latency between CPU and the northbridge.
This practice pushes components beyond their specifications and may cause erratic behavior, overheating or premature failure. Even if the computer appears to run normally, problems may appear under a heavy load. Most PCs purchased from retailers or manufacturers, such as Hewlett-Packard or Delldo not allow the user to change the multiplier or FSB settings due to the probability of erratic behavior or failure.
Evolution[ edit ] The front-side bus had the advantage of high flexibility and low cost when it was first designed. Simple symmetric multiprocessors place a number of CPUs on a shared FSB, though performance could not scale linearly due to bandwidth bottlenecks. The front-side bus was used in all Intel AtomCeleronPentiumCore 2and Xeon processor models through about