Confused about memory

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I'm about to buy a new system, motherboard will be Gigabyte GA-EX38-DQ6 with
an Intel E8400 processor running 3GHz.  The MB supports has an FSB speed of
1333 for this processor and supports up to 1200MHz for the memory including
stated sizes of 1066, 800, 533, etc.

I had intended to purchase 1066 RAM to get the best speed (I do not intend
to overclock) but some reading has stated that optimal memory performance is
obtained when the CPU & memory multipliers are in sync (??? - Whatever that

I have found some references where people talk about specific boards and
processors but can someone explain (or direct me to a web site) what is
meant by keeping these in sync with some generic simple examples.

Thank you

Re: Confused about memory

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Those "sizes" you mention are the speeds of memory memory modules in Mhz
that board supports, not the actual size of the memory modules.  The faster
memory modules tend to make for a faster computer.

Here is the link from's web page with it's list of supported

The motherboard you are looking at has 4 memory slots and can support a
maximum of 8 GB of memory.

Re: Confused about memory

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That had been my original thinking in general but it was the reading about
the multiplier syncing that has confused me.
There were statements that for optimal performance the core memory and CPU
speeds and multipliers need to be kept in sync.

i.e.  From what I've read the following is implied (particularly from
statements made that the "CPU" needs to support the memory speed chosen).
Hypothetically lets say the 3Ghz CPU has a core frequency of 200MHz to get
the 3GHz speed it has multiplier of 15.
And 800MHz memory has a core of 200MHz with a multiplier of 4.
Now 1066 memory might have a core frequency of 266MHz and also a multiplier
of 4.
Because the core frequency of the 800MHz memory and the 3GHz CPU are in sync
they are an optimal pairing.
The 1066MHz memory may be better matched with a 2.66GHZ CPU having a synched
core frequency of 266MHz and a multiplier of 10.

Now I have no idea if the above hypothetical scenario is right but I want to
find out more to make sure I choose the right pairing.  It might be possible
to get the 1066 memory and underclock its core frequency to 200MHz but put
in a multiplier of 5 giving me 1000MHz memory (admittedly not something I'm
keen on experimenting with).

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Re: Confused about memory

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When they say the CPU and memory should be in sync, they mean a 1:1
bus ratio.  The CPU bus speed is 1/4 of the FSB speed. So, if the FSB is
1333 MHz, the bus speed is 333 MHz.  The E8400 CPU has an internal
multiplier of 9, so 333 MHz x 9 gives the CPU speed of 3 GHz.

DDR2 RAM speed is twice the memory bus speed.  For a 1:1 ratio of CPU
to memory bus speeds, the memory speed would be 333 MHz x 2 which
equals 667 MHz, or PC2-5300 RAM.   The PC2-5300 means the memory
bandwidth is 5300 megabytes per second.  A bit on the slow side.

Personally, I would forget the 1:1 business and go for the 1066 MHz,
PC2-8500 RAM.   PC2-6400 800 MHz RAM is a bit cheaper.

Unless it's under load, the E8400 could be operating at a multiplier
of 6x, or 2 GHz if the BIOS has the C1E setting and it's enabled. This
setting can be disabled if you want your CPU at constant full speed.
The CPU will run a few degrees warmer at full speed, but Windows
operation will appear snappier.

Re: Confused about memory

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Nice explanation Lan D, even I was able to understand it.

Re: Confused about memory

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Thank you for the explanation.
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