Motherboards and overclocking

[tigersty1e]

http://www.newegg.com/Product/...p?item=N82E16813128059

Check this board out. It says DDR2 800 and it also has an FSB of 1333.

So if I use DDR2 800, then that would mean an FSB of 1600, right?

Then why does the board only say 1333?

 

[dreddfunk]

tiger - I'm not quite sure what you mean. If the board/CPU can take it and you have DDR2-800, you could certainly push the actual FSB to 400 and achieve the effective 1600 FSB. If you don't OC though, you're RAM will either run slower than its maximum, or you'll use a divider.

Given that you've OC'd before, I imagine you know how all this works better than I do (because I've never OC'd).

If you could clarify what you're asking, I'm sure that there are a lot of very knowledgeable people around here that can answer almost anything.

Cheers.

 

[tigersty1e]

What I'm saying is the board I posted officially supports...

FSB 1333/1066MHz

Why don't they say 1600/1333/1066MHz because this board can support 1600MHz, right?

 

[GuitarDaddy]

The numbers your quoting are what the board officially supports at stock speed, not what you can overclock the FSB too. Most modern boards will easily clock to 1600-2000 fsb.

What they mean is they support chips designed on the 1066(4x266)bus ie... conroes e6300 e6400 e6420 e6600 Q6600 etc... And the new 1333(4x333)bus ie...
e6550 e6750 e6850 ect...

 

[dreddfunk]

I understand you now, tiger - as I understand it, the memory controller that allows the use of the DDR2-800 is a different piece of hardware from the FSB. In other words, though the CPU and memory both talk through the FSB, they can and do use different speeds doing so. While DDR2-800 may be officially supported by the memory controller, that doesn't necessarily mean that the board actually officially supports the FSB necessary to run DDR2-800 at its maximum rated speed. The memory controller allows it, but that doesn't mean that the board actually has to allow and officially support an FSB to match. The RAM will just run at a lower speed or use a divider.

In reality, most of what I've heard about the P35 boards would indicate that a 400x4=1600 FSB is doable, it just depends on if your CPU has the headroom to go there. Since no Intel CPUs officially require or support 400x4=1600 FSB, there is no reason for board manufacturers to officially support running a CPU out of spec.

The board specs are simply saying, 'the memory controller allows you to use up to DDR2-800 and you can use Intel CPUs that use either a 1066 or 1333 FSB while maintaining official support.'

Now it is too bad that you can't run the the DDR2-800 RAM at maximum speed (a 1:1 ratio, RAM speed to FSB speed) without taking the FSB (and CPU) out of spec, and that this fact isn't really made explicit (though you can figure it out from the board's specifications).

It's just a weird situation that results from having one standard that's 'quad-pumped' (FSB) and another that's 'dual-pumped' (DDR2 RAM).

 

[imported_shader]

hopefully this will clear up somethings about the fsb.

the fsb will always have a constant period. fsb is not quad or dual pumped, that happens at the component/controller.

this is achieved by the different events of the clock period.

stable low (0)
transition low-high (changing from a 0 to a 1)
stable high (1)
transition high-low (changing from a 1 to a 0)

when we refer to a period, that is the time to go from a 0 to a 1 and back to a 0, which would be one clock cycle (period).

the dual 'pump' just uses the stable high and stable low signals to trigger action (for ram, strobe address, read/write cell). quad 'pump' uses all four signals.

 

[Wedge1]

Originally posted by: shader
hopefully this will clear up somethings about the fsb.

Sorry that didn't really clear anything up for a newbie reader. Interesting try though.

 

[BitByBit]

FSBs and memory speeds seem to be one of the more often misunderstood aspects of computer hardware, and it doesn't seem that any of the answers submitted so far satisfactorily address the OP's question, so I will throw in my proverbial 2p.

FSB : DRAM Bandwidth Matching

All current Intel systems feature a 'Quad Pumped ' FSB, that actually runs at a quarter of its rated speed. It is a 64-bit bus that connects the processor to the Northbridge. The memory bus connects the Northbridge to the RAM, and runs at an actual clock speed of half the rated memory clock. In dual channel mode, we have two 64-bit memory modules (effectively 128 bits, or 16 bytes) running in parallel.
An '800MHz' FSB can provide 800 * 64bits (8 bytes) = 6400MB/s of bandwidth to/from the Northbridge. So, to provide the FSB with as much bandwidth as it can handle, we need two modules of RAM running at an effective speed of: 6400MB / 16 bytes = 400MHz (DDR400).
Therefore, the general rule when matching FSB speeds to RAM speeds is simply:

RAM speed = Effective FSB / 2

This is not to say that installing memory capable of higher bandwidth than the FSB is not a good idea. In fact, memory running at higher speeds tend to have lower latencies, so you could see some benefit in running DDR2-800 with an FSB of 1333MHz, as opposed to DDR2-667 (assuming the same CL).

For those interested, 'Quad Pumping' is achieved through the use of:

1. Double Data Rate (DDR) transmission, whereby data is transmitted at 45 degrees and 135 degrees of the sine wave. This is the same method used by DDR RAM.

2. A second signal, transmitted 90 degrees out-of-phase with the first.

Taken together, we have two signals transmitting data twice per clock, giving an effective FSB speed of 4X the actual.

 

[Wedge1]

Originally posted by: BitByBit
FSBs and memory speeds seem to be one of the more often misunderstood aspects of computer hardware, and it doesn't seem that any of the answer's submitted so far satisfactorily address the OP's question, so I will throw in my proverbial 2p.

FSBRAM Bandwidth Matching

All current Intel systems feature a 'Quad Pumped ' FSB, that actually runs at a quarter of its rated speed. It is a 64-bit bus that connects the processor to the Northbridge. The memory bus connects the Northbridge to the RAM, and runs at an actual clock speed of half the rated memory clock. In dual channel mode, we have two 64-bit memory modules (effectively 128 bits, or 16 bytes) running in parallel.
An '800MHz' FSB can provide 800 * 64bits (8 bytes) = 6400MB/s of bandwidth to/from the Northbridge. So, to provide the FSB with as much bandwidth as it can handle, we need two modules of RAM running at an effective speed of: 6400MB / 16 bytes = 400MHz (DDR400).
Therefore, the general rule when matching FSB speeds to RAM speeds is simply:

RAM speed = Effective FSB / 2

This is not to say that installing memory capable of higher bandwidth than the FSB is not a good idea. In fact, memory running at higher speeds tend to have lower latencies, so you could see some benefit in running DDR2-800 with an FSB of 1333MHz, as opposed to DDR2-667 (assuming the same CL).

For those interested, 'Quad Pumping' is achieved through the use of:

1. Double Data Rate (DDR) transmission, whereby data is transmitted at 45 degrees and 135 degrees of the sine wave. This is the same method used by DDR RAM.

2. A second signal, transmitted 90 degrees out-of-phase with the first.

Taken together, we have two signals transmitting data twice per clock, giving an effective FSB speed of 4X the actual.

Excellent! Very newbie friendly!!