C2D Overclocking Techniques Asus P5B-Plus

I read in another thread in this group that you should:

"Unlink the memory clock from the CPU clock and run the memory at its stock
specifications" (thanks to Phil Weldon)

In my P5B-Plus BIOS (after setting the AI Overclock to manual) I have a
setting for CPU frequency, adjustable in 1 MHz increments. This setting is
linked to DRAM frequency as any change in CPU frequency reflects as an
equivalent change in DRAM frequency.

To keep my memory in spec, I originally set my DRAM frequency to DDR2-533MHz
because I knew it would increase with increases in CPU frequency.
Presently, I've raised the CPU frequency from the original 267 to 333, which
has put my DRAM frequency at DDR2-667MHz.
That's a modest overclock for my 6420, now running at 2.67GHz.

Now that I've acquired a 3rd party HSF (the Intel HSF is barely able to cope
with the current settings), I'd like to raise the CPU frequency in small
increments, but I really prefer to leave my DRAM frequency where it is.

The only settings available for DRAM frequency are DDR2-533, DDR2-667,
DDR2-800, DDR2-889, DDR2-1067 and AUTO.
Unfortunately the manual does not describe the effects of using AUTO, but
that would appear to be the only possible way to unlink the memory clock
from the CPU clock, if AUTO somehow means set by interrogating the memory
modules themselves (used to be called "by SPD" IIRC).

Am I on the right track to decoupling CPU clock and DRAM frequency, or is
there some other BIOS setting I've missed completely?

TIA for any enlightenment/suggestions.

'Peter van der Goes' wrote, in part:
|I read in another thread in this group that you should:
|
| "Unlink the memory clock from the CPU clock and run the memory at its
stock
| specifications" (thanks to Phil Weldon)
|
| In my P5B-Plus BIOS (after setting the AI Overclock to manual) I have a
| setting for CPU frequency, adjustable in 1 MHz increments. This setting is
| linked to DRAM frequency as any change in CPU frequency reflects as an
| equivalent change in DRAM frequency.
|
| To keep my memory in spec, I originally set my DRAM frequency to
DDR2-533MHz
| because I knew it would increase with increases in CPU frequency.
| Presently, I've raised the CPU frequency from the original 267 to 333,
which
| has put my DRAM frequency at DDR2-667MHz.
| That's a modest overclock for my 6420, now running at 2.67GHz.
_____

Overclocking is a voyage of discovery. Different motherboard manufacturers
customize BIOS settings in different ways. Some chip sets allow setting
parameters that are not available when other chip sets are used. Generally
the motherboard manuals provided don't offer much explanation, and seem to
be the product of several translations back and forth among several
languages - and even different concepts of math B^)

Form a cursory look at the manual for your P5B Plus motherboard, it seems to
me that selecting a memory speed from the list under 'DRAM Frequency' in the
'Advanced Chipset Settings' page

[Auto]
[DDR2 - 533MHz]
[DDR2 - 667MHz]
[DDR2 - 800MHz]
[DDR2 - 889MHz]
[DDR2- 1067MHz]

sets the memory speed to specific frequencies that are not linked to the CPU
speed, with the [Auto Selection] possibly a setting to link the Memory Clock
to a multiple of the CPU Clock, probably 1:2].

I'd guess that you are wrong in assuming that increasing the CPU clock speed
increases the Memory clock speed UNLESS the 'DRAM Frequency' setting is
[AUTO]. The English version of the manual is ambiguous on this and other
points. There does not seem to be the flexibility in the BIOS settings
that, for example, the nVidia 680i chipset has for memory frequency where
any memory bus frequency can be set independently from the FSB frequency
(though there is some granularity.)

For your particular concern, I'd set the 'DRAM Frequency' to the
specification of your memory modules, and assume that the memory clock
frequency would be fixed. If you, after getting a stable CPU overclock,
wish to overclock your memory, it seems that only certain fixed memory speed
steps are avaliable in the BIOS. Perhaps the ASUS OS based overclocking
application has additional flexibility.

Try it and check the results.

Phil Weldon


"Peter van der Goes" <> wrote in message
news:VGCgi.235360$...
|I read in another thread in this group that you should:
|
| "Unlink the memory clock from the CPU clock and run the memory at its
stock
| specifications" (thanks to Phil Weldon)
|
| In my P5B-Plus BIOS (after setting the AI Overclock to manual) I have a
| setting for CPU frequency, adjustable in 1 MHz increments. This setting is
| linked to DRAM frequency as any change in CPU frequency reflects as an
| equivalent change in DRAM frequency.
|
| To keep my memory in spec, I originally set my DRAM frequency to
DDR2-533MHz
| because I knew it would increase with increases in CPU frequency.
| Presently, I've raised the CPU frequency from the original 267 to 333,
which
| has put my DRAM frequency at DDR2-667MHz.
| That's a modest overclock for my 6420, now running at 2.67GHz.
|
| Now that I've acquired a 3rd party HSF (the Intel HSF is barely able to
cope
| with the current settings), I'd like to raise the CPU frequency in small
| increments, but I really prefer to leave my DRAM frequency where it is.
|
| The only settings available for DRAM frequency are DDR2-533, DDR2-667,
| DDR2-800, DDR2-889, DDR2-1067 and AUTO.
| Unfortunately the manual does not describe the effects of using AUTO, but
| that would appear to be the only possible way to unlink the memory clock
| from the CPU clock, if AUTO somehow means set by interrogating the memory
| modules themselves (used to be called "by SPD" IIRC).
|
| Am I on the right track to decoupling CPU clock and DRAM frequency, or is
| there some other BIOS setting I've missed completely?
|
| TIA for any enlightenment/suggestions.
|
|

"Phil Weldon" <> wrote in message
news:swDgi.1675$ nk.net...
> 'Peter van der Goes' wrote, in part:
>
> Overclocking is a voyage of discovery. Different motherboard
> manufacturers
> customize BIOS settings in different ways. Some chip sets allow setting
> parameters that are not available when other chip sets are used.
> Generally
> the motherboard manuals provided don't offer much explanation, and seem to
> be the product of several translations back and forth among several
> languages - and even different concepts of math B^)
>
> Form a cursory look at the manual for your P5B Plus motherboard, it seems
> to
> me that selecting a memory speed from the list under 'DRAM Frequency' in
> the
> 'Advanced Chipset Settings' page
>
> [Auto]
> [DDR2 - 533MHz]
> [DDR2 - 667MHz]
> [DDR2 - 800MHz]
> [DDR2 - 889MHz]
> [DDR2- 1067MHz]
>
> sets the memory speed to specific frequencies that are not linked to the
> CPU
> speed, with the [Auto Selection] possibly a setting to link the Memory
> Clock
> to a multiple of the CPU Clock, probably 1:2].
>
> I'd guess that you are wrong in assuming that increasing the CPU clock
> speed
> increases the Memory clock speed UNLESS the 'DRAM Frequency' setting is
> [AUTO]. The English version of the manual is ambiguous on this and other
> points. There does not seem to be the flexibility in the BIOS settings
> that, for example, the nVidia 680i chipset has for memory frequency where
> any memory bus frequency can be set independently from the FSB frequency
> (though there is some granularity.)
>
> For your particular concern, I'd set the 'DRAM Frequency' to the
> specification of your memory modules, and assume that the memory clock
> frequency would be fixed. If you, after getting a stable CPU overclock,
> wish to overclock your memory, it seems that only certain fixed memory
> speed
> steps are avaliable in the BIOS. Perhaps the ASUS OS based overclocking
> application has additional flexibility.
>
> Try it and check the results.
>
> Phil Weldon
>
I'll take a chance with it and let you know.
The reason I'm a bit leery is that after selecting DDR2-533MHz for DRAM
Frequency, making changes to the CPU Clock setting simultaneously changes
the displayed speed in DRAM Frequency.

I don't own a P5B. I am using a P5W DH instead.
Here is how I understand what's happening for me:
There is a link between the FSB frequency and the speed of the mem. The link
comes from the fact that the CPU (or FSB) clock and the mem interface clock
both derive from the same basic clock. So that there can only be fractional
relations between them, like 1:1, 5:4, 4:3, etc. This is what is called the
CPU/mem (or mem/CPU?) ratio.
So what happens?
When you choose one FSB frequency for the CPU, the advanced chipset settings
will present you with DDR2-xxxMHz values which are indeed the FSB multiplied
by the various fractions I mentionned. You can choose whichever value, at
will, but provided you don't go too high and go over what the mem can do.
Now, if you start by choosing DDR2-533MHz (which would correspond to a
266MHz FSB and a 1:1 ratio) and subsequently change the FSB to 300MHz, then
what you will find in chipset settings for the 1:1 ratio is DDR2-600MHZ. And
other values which correspond to the 5:4, etc ratios of 300MHz. If 600MHz
goes above the speed your mem can cope with, simply choose another value
which, for example, would correspond to a 4:5 ratio (in this case,
DDR2-480MHz).
In other words, because it is the way the BIOS works (you choose an FSB
frequency, and in fact a CPU/mem ratio although it is presented as a mem
speed value), choose the FSB first and then adjust the chipset settings for
the mem.
That's how it works for my P5W DH, I guess it is the same for the P5B.
Sorry I cannot be more precise on the DDR2-xxxMHz (or CPU/mem ratios)
accessible, as I am not home where I use my P5W.
I am not sure this is all clear?

"Peter van der Goes" <> wrote in message
news:0vGgi.652319$...
>
> "Phil Weldon" <> wrote in message
> news:swDgi.1675$ nk.net...
> > 'Peter van der Goes' wrote, in part:
> >
> > Overclocking is a voyage of discovery. Different motherboard
> > manufacturers
> > customize BIOS settings in different ways. Some chip sets allow setting
> > parameters that are not available when other chip sets are used.
> > Generally
> > the motherboard manuals provided don't offer much explanation, and seem
to
> > be the product of several translations back and forth among several
> > languages - and even different concepts of math B^)
> >
> > Form a cursory look at the manual for your P5B Plus motherboard, it
seems
> > to
> > me that selecting a memory speed from the list under 'DRAM Frequency' in
> > the
> > 'Advanced Chipset Settings' page
> >
> > [Auto]
> > [DDR2 - 533MHz]
> > [DDR2 - 667MHz]
> > [DDR2 - 800MHz]
> > [DDR2 - 889MHz]
> > [DDR2- 1067MHz]
> >
> > sets the memory speed to specific frequencies that are not linked to the
> > CPU
> > speed, with the [Auto Selection] possibly a setting to link the Memory
> > Clock
> > to a multiple of the CPU Clock, probably 1:2].
> >
> > I'd guess that you are wrong in assuming that increasing the CPU clock
> > speed
> > increases the Memory clock speed UNLESS the 'DRAM Frequency' setting is
> > [AUTO]. The English version of the manual is ambiguous on this and
other
> > points. There does not seem to be the flexibility in the BIOS settings
> > that, for example, the nVidia 680i chipset has for memory frequency
where
> > any memory bus frequency can be set independently from the FSB frequency
> > (though there is some granularity.)
> >
> > For your particular concern, I'd set the 'DRAM Frequency' to the
> > specification of your memory modules, and assume that the memory clock
> > frequency would be fixed. If you, after getting a stable CPU overclock,
> > wish to overclock your memory, it seems that only certain fixed memory
> > speed
> > steps are avaliable in the BIOS. Perhaps the ASUS OS based overclocking
> > application has additional flexibility.
> >
> > Try it and check the results.
> >
> > Phil Weldon
> >
> I'll take a chance with it and let you know.
> The reason I'm a bit leery is that after selecting DDR2-533MHz for DRAM
> Frequency, making changes to the CPU Clock setting simultaneously changes
> the displayed speed in DRAM Frequency.
>

"M. R. Carleer" <> wrote in message
news:f60a8i$rpl$...
>I don't own a P5B. I am using a P5W DH instead.
> Here is how I understand what's happening for me:
> There is a link between the FSB frequency and the speed of the mem. The
> link
> comes from the fact that the CPU (or FSB) clock and the mem interface
> clock
> both derive from the same basic clock. So that there can only be
> fractional
> relations between them, like 1:1, 5:4, 4:3, etc. This is what is called
> the
> CPU/mem (or mem/CPU?) ratio.
> So what happens?
> When you choose one FSB frequency for the CPU, the advanced chipset
> settings
> will present you with DDR2-xxxMHz values which are indeed the FSB
> multiplied
> by the various fractions I mentionned. You can choose whichever value, at
> will, but provided you don't go too high and go over what the mem can do.
> Now, if you start by choosing DDR2-533MHz (which would correspond to a
> 266MHz FSB and a 1:1 ratio) and subsequently change the FSB to 300MHz,
> then
> what you will find in chipset settings for the 1:1 ratio is DDR2-600MHZ.
> And
> other values which correspond to the 5:4, etc ratios of 300MHz. If 600MHz
> goes above the speed your mem can cope with, simply choose another value
> which, for example, would correspond to a 4:5 ratio (in this case,
> DDR2-480MHz).
> In other words, because it is the way the BIOS works (you choose an FSB
> frequency, and in fact a CPU/mem ratio although it is presented as a mem
> speed value), choose the FSB first and then adjust the chipset settings
> for
> the mem.
> That's how it works for my P5W DH, I guess it is the same for the P5B.
> Sorry I cannot be more precise on the DDR2-xxxMHz (or CPU/mem ratios)
> accessible, as I am not home where I use my P5W.
> I am not sure this is all clear?
>
Very clear, actually
As Phil put it, "overclocking is a voyage of discovery". I've discovered
that these motherboards with the Intel 965 chipset don't allow separation of
CPU and memory speeds. So now I'll see if I can push the memory a bit more


Thanks very much to both you and Phil for the information.

I am not sure it comes from the chipset. It might come from a clock
generator on the mobo. I don't know.
Anyway, what is to be remembered is that in the BIOS you don't choose the
CPU freq and the mem freq, but instead the CPU freq and a ratio between that
and the mem freq. In the chipset settings, they present the mem freq which
would derive from the chosen CPU freq and ratio, but what you effectively
choose is the ratio without knowing. Of course, once you choose the ratio,
changing the CPU freq also changes the mem freq as the ratio remains
constant.
Choosing Auto, the BIOS chooses the ratio for you so that the resulting mem
freq is <= than the maximum defined by the mem module itself in the spd,
choosing preferably the 1:1 ratio. Once again, that's what I found for the
P5W. It might be different for the P5B.

Oh, and you are welcome: it is the purpose of the newsgroups, to try to help
one another.

"Peter van der Goes" <> wrote in message
news:EMOgi.1835$%...
>
> "M. R. Carleer" <> wrote in message
> news:f60a8i$rpl$...
> >I don't own a P5B. I am using a P5W DH instead.
> > Here is how I understand what's happening for me:
> > There is a link between the FSB frequency and the speed of the mem. The
> > link
> > comes from the fact that the CPU (or FSB) clock and the mem interface
> > clock
> > both derive from the same basic clock. So that there can only be
> > fractional
> > relations between them, like 1:1, 5:4, 4:3, etc. This is what is called
> > the
> > CPU/mem (or mem/CPU?) ratio.
> > So what happens?
> > When you choose one FSB frequency for the CPU, the advanced chipset
> > settings
> > will present you with DDR2-xxxMHz values which are indeed the FSB
> > multiplied
> > by the various fractions I mentionned. You can choose whichever value,
at
> > will, but provided you don't go too high and go over what the mem can
do.
> > Now, if you start by choosing DDR2-533MHz (which would correspond to a
> > 266MHz FSB and a 1:1 ratio) and subsequently change the FSB to 300MHz,
> > then
> > what you will find in chipset settings for the 1:1 ratio is DDR2-600MHZ.
> > And
> > other values which correspond to the 5:4, etc ratios of 300MHz. If
600MHz
> > goes above the speed your mem can cope with, simply choose another value
> > which, for example, would correspond to a 4:5 ratio (in this case,
> > DDR2-480MHz).
> > In other words, because it is the way the BIOS works (you choose an FSB
> > frequency, and in fact a CPU/mem ratio although it is presented as a mem
> > speed value), choose the FSB first and then adjust the chipset settings
> > for
> > the mem.
> > That's how it works for my P5W DH, I guess it is the same for the P5B.
> > Sorry I cannot be more precise on the DDR2-xxxMHz (or CPU/mem ratios)
> > accessible, as I am not home where I use my P5W.
> > I am not sure this is all clear?
> >
> Very clear, actually
> As Phil put it, "overclocking is a voyage of discovery". I've discovered
> that these motherboards with the Intel 965 chipset don't allow separation
of
> CPU and memory speeds. So now I'll see if I can push the memory a bit more
>
>
> Thanks very much to both you and Phil for the information.
>