mwebsurfer said:
What is the fastest memory that I can use in this board.
ASUS says in their manual that it takes 400ddr. With the
latest bios upgrade can it take anything higher? I have
not yet begun to build my pc yet and wonder what to buy.
I have the MB,3.4 ghz 800 fsb processor,case and sony
16x burner. Any help will be appreciated.
In the downloadable user manual, there is mention of "[400 MHz]
[533 MHz] [600 MHz]" for the RAM, but no context is given
(whether that is with FSB800 or FSB533 processor). The Intel
915 datasheet was no help to me either.
You would guess that it means a higher memory to CPU ratio
is selectable, but the real question would be, whether running
the memory asynchronous, versus synchronous at DDR400, provides
a benefit or not. In any case, with four sticks of RAM, you
won't be able to go very far with that control setting, before
you start to see memory errors. With two sticks, more will
be possible, but perhaps the amount of Vdimm available, and
the type of memory will influence your options as well.
Due to the granularity of the settings, and the fact that
the choices are so far apart, I would expect you will be
overclocking the FSB, and taking any resulting memory
overclock that goes with it.
To work through some examples, we'll assume you aren't made
of money, and can afford a 3GHz processor. Prescott processors
are good for about a 4GHz overclock, without invoking cryogenic
cooling.
With a memory setting of DDR400...
Set CPU clock to 200MHz ==> FSB800 DDR400 3.00GHz core
Set CPU clock to 225MHz ==> FSB900 DDR450 3.38GHz core
Set CPU clock to 250MHz ==> FSB1000 DDR500 3.75GHz core
Set CPU clock to 275MHz ==> FSB1100 DDR550 4.13GHz core
Now, in the above examples, with four sticks of RAM, you will
be able to get somewhere between DDR450 and DDR500. You
can probably manage DDR450 but not much more than that. With
two sticks more is possible (but I don't know how far a 915
has been pushed, and how much voltage it takes). The Athlon64
has managed DDR600 with two sticks, but I don't know if a
915 can get there or not. It looks like you could buy two sticks
of DDR533 memory, and try to take a 3GHz processor to 4GHz.
The DDR533 setting doesn't look nearly as useful, with our
3GHz sample processor...
With a memory setting of DDR533...
Set CPU clock to 200MHz ==> FSB800 DDR533 3.00GHz core
Set CPU clock to 225MHz ==> FSB900 DDR600 3.38GHz core
In this case, there isn't a lot of room to overclock the
core. The DDR533 setting would be useful if you bought
an expensive processor, and were not expecting to lift
the core much more. Maybe a 3.6GHz processor, lifted
by using the 225MHz setting to 4.05GHz, would be the
best expectation. Then you would need uber-DDR600 RAM,
just to see that happen.
I would think a reasonably priced midrange processor, plus
two sticks of some DDR533 memory, should give you room to
experiment. If you wanted to buy an expensive processor,
there is not a lot of wiggle room - either you use the
DDR400 memory setting (and some DDR500 memory would almost
be overkill then), or use the DDR533 memory setting, and
virtually eliminate the opportunity to overclock.
I hope that clarifies the arithmetic a bit. The reason
I am hedging my bets, is I haven't done the research in
the private forums, as to whether the majority of 915
northbridge chips, are capable of DDR500+ speeds. You wouldn't
want to spend the big money on DDR600 memory, only to find
your 915 is a stinker.
Paul
