I have a Gigabyte GA-X48-DS4 board with an Intel E8400 cpu. I know the settings needed above, but I lack the "why" of the values. Any info in hardback or online on the "why" of the interrelation would be appreciated. In a related matter I understand that it is not possible to make a 64 bit install of an XP pro upgrade over a 32 bit version. Is this true? Does it hold for an install of a W7 upgrade also?
More about :host frequency multiplier fsb clock cycle
Let's see if I can figure out what you are asking ...
Definition time (attention purists, I'm talking about DDR2 and I'm simplifying a little ):
Core2 CPU's use a frontside bus (FSB). The FSB is a thing with two main characteristics: speed which is usually defined in MHz and width which in the Core2's is 64 bits wide. We are concerned with the speed.
Using the Q6600 as an example, the FSB (also sometimes known as "host") frequency is 266 MHz. The matching DDR2 memory clock for that frequency is 533 MHz (266 X 2). DDR2 memory transfers two chunks of data for each bus cycle, hence double the frequency. So, to run a 1:1 ratio at an FSB of 266 MHz, we need DDR2-533 RAM. What CPUZ does is a little confusing. It will tell you that the memory frequency is 266 MHz for a 1:1 ratio. So each FSB cycle generates 2 memory clocks.
The FSB clock is 1066 MHz (266 X 4). The bus is "quad pumped". It transfers 4 chunks of data into and out of the CPU each cycle. So each FSB cycle generates 4 FSB clocks.
Now, if you increase the FSB frequency to 333 MHz, the corresponding memory clock is 667 MHz and the FSB clock is 1333 MHz.
Thanks. jsc, for the information. I see from the general replies that a copy of Computer Engineering is the likely source for this information. I thought that "homebuilt" meant more depth than sticking parts together.
perhaps WE did not understand your question .. If you just want the stock timings then the datasheet that came with DDR3 will tell you the correct timings.
You need to enter the CAS values from the RAM data-sheet into the BIOS/SETUP ?*MANUALLY* and must SAVE before exit from setup ... go back in (on restart) and check that the settings "stuck" ... good to go.
If you want to know about OC, with a particular combo of mobo/DDR3/CPU then you might drop in on the TOM's Overclock Forum ... Go to "Forums" tab, on Tom's mainpage and select Overclock Forum.