What exactly are you multiplying when you change the multiplier?

[Johnbear007]

Ok, I mean I understand that 11 x 200 FSB = 2200 on my barton. It is derived from the front side bus, so I dont mean I dont understand what it is called.

What I mean, is, when I say change the multiplier to 12 x 200 and now have a 2.4ghz processor, what exactly is happening. Is there a good guide that explains the frequency of the chip and how its derived?

 

[VIAN]

using the 3200

200 is the Fron-side-bus. That is how fast the North-bridge chip communticates with the processor and the ram.

A cpu also has an external clock speed which is 200MHz - front side bus or fsb.

multiplying 11 the fsb is how fast the internal clock speed is.

basically internal clock speed is the quickness of the calculations the cpu can perform inside the cpu without using any outside resources, while external clock speed needs outside resources.

did this help at all your question is kind of confusing.

 

[VIAN]

If that didn't answer your question, then this might. I'm not done with my engineering course, still doing associates, but here's my guess from my experience.

There is a circuit called a Crystal Clock that generates a clock signal or frequency, which is the external clock. The motherboard BIOS then sends a signal to the cpu that tells it which number to multiply the frequency, based on the cpu. Then the clock signal gets sent to multiple circuits for multiplication. I forgot how exactly to multiply frequency and my books are all difficult to get so I'm just gonna say Idk on that. It might be done differently, but this is my first guess.

 

[myocardia]

Okay, let me take a shot at this. No offense to Vian and his engineering courses, but this is quite a bit more simple (in layman's terms, in other words). When you change your multiplier, you are changing only the speed of the processor itself. That's why changing the fsb is the way to overclock. Having a faster processor, with the same slower chipset speed, memory speed, etc. doesn't do you much good. But, when you raise the fsb, you are making the entire system faster. Raising the fsb makes the processor run faster too, but, it lets the memory and the chipset run as fast as the cpu, so they work much better together as a "team". Capiche?

 

[blcjr]

Raising the fsb makes the processor run faster too, but, it lets the memory and the chipset run as fast as the cpu...

You started off right, but derailed at the end with the preceding statement. If you change the multiplier, then you make the CPU work faster, but not the memory subsystem. If raise the fsb, then you get the memory subsystem to work faster. But it will never work as fast as the CPU. The CPU is always going to run X times faster, where X is the multiplier.

Think about it. If you take a 133 fsb system, and clock it so that the cpu is 10x200, what is the speed of the CPU? 2000. And what is the speed of the memory subsystem? 200.

 

[VIAN]

There is no FSB with the A64 though. The entire system runs at CPU performance.

 

[acx]

Athlon64 has integrated memory controllers that hide the latency of main memory from the CPU. The memory is still running at slower DDR speeds it's just that the path from the CPU to the memory controller is now on chip. The main bottleneck of slow DRAM is still there.

 

[Jeff7181]

Originally posted by: VIAN
There is no FSB with the A64 though. The entire system runs at CPU performance.

Not exactly. There is no FSB... because the FSB is the term given to the bus between the CPU and the Northbridge, which is where the memory controller is. Since the memory controller is onboard, there is no Northbridge anymore as we once knew it. So how does the processor communicate with the outside world? The Hyper-Transport link. This operates at anywhere from 200-1600 Mhz in multiples of 200... so 200, 400, 800, 1600.
The CPU now has a direct link to the RAM... there is no chipset like the northbridge in between now, which is the main reason for the increased pin count of the Athlon-64 since processors have had a 64 bit data bus ever since the origional Pentium I believe. Now not only does it have an external bus (Hyper-Transport), it has a separate memory bus.
The internal clock speed is still derived in the same manner... external bus x multiplier = internal clock speed.

*EDITED FOR LATE NIGHT TYPOS*

 

[myocardia]

Originally posted by: blcjr

Raising the fsb makes the processor run faster too, but, it lets the memory and the chipset run as fast as the cpu...

You started off right, but derailed at the end with the preceding statement. If you change the multiplier, then you make the CPU work faster, but not the memory subsystem. If raise the fsb, then you get the memory subsystem to work faster. But it will never work as fast as the CPU. The CPU is always going to run X times faster, where X is the multiplier.

Think about it. If you take a 133 fsb system, and clock it so that the cpu is 10x200, what is the speed of the CPU? 2000. And what is the speed of the memory subsystem? 200.

Hmmm, I would have sworn that I said in my post that I was trying to make it so this guy could understand it. Why don't you re-read my post, and see if that's not exactly what I told the guy... If I were wanting to make it as complicated as possible, I would have included a link to the National Engineering Society's website, just to make sure that he understood absolutely nothing that he read!