Archived from groups: alt.comp.periphs.mainboard.asus (More info?)
In article <BVsOe.32226$Qh7.firstname.lastname@example.org>, "Jean"
> I'm coming from Intel and this is my first AMD CPU and I
> don't know how to overclock ?
> For my previous pentium it was easy, only had to increase
> FSB and adjust the memory ratio setting.
> My memory is OCZ PC3500 433mhz, my MB is Asus SLI premium
> There is a lot of settings..... MAX memory clock ? Hyper transport ?
> It's easy to overclock the CPU but then the hyper transport
> speed will be lower, memory too ?? If I overclock the memory
> then the CPU multiplier will go down.. I'm lost.
> What must I do exactly in the bios to overclock to 2.37 ghz
> (11x217mhz) and keeping the memory speed to 433hz ??
Well, every time I try to work through an example, I get the
wrong answer. What I'll do, is give you a reading assignment,
and then you can explain it to me :-)
The process seems to work like this. You feed the CPU a clock.
There is one multiplier that sets the Hypertransport link rate,
and you select that multiplier so it is less than the max for
the link. For example, 4*217 < 1000MHz and might work for you.
This setting isn't too critical, as the video card doesn't really
need all that bandwidth. And the chipset interfaces hardly
make a dent in it.
The next multiplier, is the one used to make the core clock. I.e.
Your BIOS also has "objective" settings for the memory. Those
objectives are based on a base clock choice of 200Mhz. With
the newest processors, some new objectives have been added, but
they are not documented in downloadable AMD docs. The objectives
that are mentioned in official AMd docs are DDR400, DDR333, DDR266
and the like. That is a memory clock of 200, 166, 133 and so on.
When you set an objective, the BIOS is selecting a divider, which
divides down from the processor core clock rate. Say a memory divider
of 13 was being used. (11*217)/13 = 184MHz. The processor uses the
nearest divider that runs the memory at the objective speed or
The objective setting exercise is done based on assuming no
overclock is being applied. If you select DDR333 as your objective,
but you overclock the FSB to 220 (10% overclock), that means the
memory ends up running 10% faster as well - like DDR366. In a way,
it is like a previous generation of motherboards - the memory
setting is not indicative of the true speed, but is more "symbolic"
of whatever divider is being used inside the CPU.
This table is fun. Change the clock from its 200MHz default, and
watch the fun. Not all motherboards support all the data in the
table, so your BIOS may not offer as many memory "objectives" as
One thing you will note, is using the x.5 core multipliers is a
waste, as the memory runs slower than it has to. The full integer
core multipliers are a better choice.
Using the same tool this way, selects the best combination of
settings, given your objectives. Now, I tried typing in your
settings above, and ended up not understanding the answer entirely
(I couldn't figure out where 13:12 comes from - maybe this is
a feature of the Rev.E chips I don't know about).
If I use this setting, the second line returned makes sense, as
by selecting an objective of "200MHz" for the RAM, setting the
FSB to 217, the RAM will run at 217 as well. That would be the
1:1 divider. I don't understand the first line, where 13:12 is
shown. Perhaps when you look at your BIOS interface, it will
CPU 2387 100% (most important)
RAM 217 10% (hardly important, not a priority to meet objective)
HTT 1000 0%
HTT/FSB 217 0%
Multi 11x ---
Here are some other links, in no particular order. Maybe after
browsing though these, it will be clearer:
(Dual core a bit more hungry for memory. Single cores don't
benefit all that much from memory bandwidth optimization. I
cannot wait to see this article repeated, when multi-threaded
games are available.)