Howdy!
I've read the forums, researched on the net, visited the manufacturers websites, and I'm STILL confused by Ram speeds for Intel (specifcally Conroe) systems. Would anyone be as kind as to answer the following question please?
My understand is as follows:
In a Intel Conroe system, the CPU is connected to the memory via a North Bridge, in the following arrangement:
CPU <---> North Bridge <---> Memory
The Front Side Bus (FSB) is the speed of the CPU -> North Bridge connection, and by default, is 266Mhz for all Conroe systems. This is double data rate (DDR), meaning an operation occurs at the rising and falling edge of the clock signal, AND DDR2'd meaning an operation occurs at the start and end of the falling edge, as well as the start and end of the rising edge, meaning in effect operations occurs 4 times per clock cycle, or quad-pumped as Intel likes to call it.
This gives an effective communication speed of 4x266Mhz --> 1066Mhz which is the FSB speed claimed in the Intel headlines.
Now the interesting part - the speed of the communication between North Bridge and memory. You can set some dividers in the North Bridge such that the CPU->NorthBridge and NorthBridge->Memory data rates differ. There are a number of divider settings (user set in the motherboard BIOS presumably), but assuming the CPU wants to speak to the memory as fast as possible, a 1:1 ratio would be nice (in reality the North Bridge is connected to various other devices which might require communication with the CPU, thus stealing CPU->NorthBridge cycles).
This is where I start to get confused. From the excellent thread http://forums.overclockers.co.uk/showthread.php?t=17592348
I see that a E6700 runs at a 10 multiplier of the FSB. So at stock speeds, a E6700 has a 266Mhz FSB x10 -> 2.67 Ghz CPU. So far so good.
BUT - how does memory speed relate to this 266Mhz? I see that DDR2 667Mhz is fine for 266Mhz FSB, or 667x8 -> PC5300 as RAM manufacturers like to talk in bytes not bits. Is it just doubled, which is why 667Mhz memory is happy to run at a FSB speed of 330Mhz max (within spec)? In which case, at stock speeds you only in fact need 532Mhz memory, --> PC4256 if such a thing existed?
Which leads me onto what I actually want to know. With a E6700, I'd like to buy 4Gb memory which will allow me to do a "mild" overclock, say into the 3.2Ghz region, at a 1:1 multiplier. This is a 320Mhz FSB, which from the table requires PC6400. My question is this: If I buy "any old" PC6400, and run at 320Mhz FSB, am I in fact running well within the manufactures tested speed?.
I like the look of the new Corsair DDR2 ram (what can I say - I like flashing lights <blush>), but this may or may not be particularly good "overclocking" ram from peoples comments about Corsair. However would I actually be overclocking the ram at my desired speed?
Woops I've rambled on a bit, I'm sorry!
I've read the forums, researched on the net, visited the manufacturers websites, and I'm STILL confused by Ram speeds for Intel (specifcally Conroe) systems. Would anyone be as kind as to answer the following question please?
My understand is as follows:
In a Intel Conroe system, the CPU is connected to the memory via a North Bridge, in the following arrangement:
CPU <---> North Bridge <---> Memory
The Front Side Bus (FSB) is the speed of the CPU -> North Bridge connection, and by default, is 266Mhz for all Conroe systems. This is double data rate (DDR), meaning an operation occurs at the rising and falling edge of the clock signal, AND DDR2'd meaning an operation occurs at the start and end of the falling edge, as well as the start and end of the rising edge, meaning in effect operations occurs 4 times per clock cycle, or quad-pumped as Intel likes to call it.
This gives an effective communication speed of 4x266Mhz --> 1066Mhz which is the FSB speed claimed in the Intel headlines.
Now the interesting part - the speed of the communication between North Bridge and memory. You can set some dividers in the North Bridge such that the CPU->NorthBridge and NorthBridge->Memory data rates differ. There are a number of divider settings (user set in the motherboard BIOS presumably), but assuming the CPU wants to speak to the memory as fast as possible, a 1:1 ratio would be nice (in reality the North Bridge is connected to various other devices which might require communication with the CPU, thus stealing CPU->NorthBridge cycles).
This is where I start to get confused. From the excellent thread http://forums.overclockers.co.uk/showthread.php?t=17592348
I see that a E6700 runs at a 10 multiplier of the FSB. So at stock speeds, a E6700 has a 266Mhz FSB x10 -> 2.67 Ghz CPU. So far so good.
BUT - how does memory speed relate to this 266Mhz? I see that DDR2 667Mhz is fine for 266Mhz FSB, or 667x8 -> PC5300 as RAM manufacturers like to talk in bytes not bits. Is it just doubled, which is why 667Mhz memory is happy to run at a FSB speed of 330Mhz max (within spec)? In which case, at stock speeds you only in fact need 532Mhz memory, --> PC4256 if such a thing existed?
Which leads me onto what I actually want to know. With a E6700, I'd like to buy 4Gb memory which will allow me to do a "mild" overclock, say into the 3.2Ghz region, at a 1:1 multiplier. This is a 320Mhz FSB, which from the table requires PC6400. My question is this: If I buy "any old" PC6400, and run at 320Mhz FSB, am I in fact running well within the manufactures tested speed?.
I like the look of the new Corsair DDR2 ram (what can I say - I like flashing lights <blush>), but this may or may not be particularly good "overclocking" ram from peoples comments about Corsair. However would I actually be overclocking the ram at my desired speed?
Woops I've rambled on a bit, I'm sorry!