davej wrote:
> The manual says board has cpu multiplier and cpu lock free facility. In bios
> the cpu adjusts are all greyed out ? How can I change fsb? tia , dave
>
There are two mechanisms you can use for overclocking. Multiplier
adjustment, and input clock increase. Clock times multiplier
gives core clock rate: i.e. 200Mhz x 15 = 3GHz.
In the manual, I don't see an option in the BIOS to change the
CPU frequency. So there is no way to change the input clock,
at the BIOS level.
For multiplier, there are a couple situations.
1) ES (engineering sample) processors, or perhaps some of the
extreme edition processors, have unlocked multipliers. That
allows a more arbitrary setting of the multiplier. Neither
of those processor types is cheap, or readily available.
Most people can only afford the more economical, locked
processors. ES chips should really only be given to
engineers who are developing computer products, and
should not be in general circulation.
2) On something like a regular P4 processor, the multiplier is
locked.
So, then, what is "lock free" ?
The P4 processors have a couple multiplier values. They have
a "safe" value of 14x, and then they have their "normal"
multiplier.
Let's take an example of a 3.0GHz P4 with FSB800. The FSB is
quad pumped, and the real clock is 200MHz. If we divide
3000 / 200 = 15x. The "normal" multiplier of that processor,
is 15x. The normal input clock is 200MHz, it gets multiplied
by 15, to give 3.0GHz core clock speed.
Now, the Vcore regulator on the motherboard, can be designed
for a couple power levels. If the motherboard maker wants to
save a few bucks, they design for the lower level. Otherwise,
they design for the higher level.
Say a user plugs a high power P4 processor, into a motherboard
that only supports low power processors. What they decided to
do, is have the option of dropping the multiplier to 14x. On
the 3GHz processor, this gives a slight power reduction.
On a 3.6GHz processor, the multiplier difference would be a bit
bigger. The multiplier would drop from 18x to 14x.
There is a bit in the P4 processor, called "PRB", and it signals
the processor type to the BIOS. Based on reading the PRB, a
motherboard with a weak Vcore regulator, would select the
"safe" multiplier, thus avoiding damage to the processor.
That was the design intent of this feature, something along
those lines:
http://www.tomshardware.com/2004/09/16/asus_bios_unlocks_p4_overclocki...potenti
The feature was invented, to protect a motherboard with a
weak Vcore regulator design. But the motherboard companies
latched onto the two multiplier values, and pretended this
was a feature they discovered through research in the lab.
The idea is, by dropping the multiplier, an overclocker could
raise the input clock, and end up with overclocked RAM. So
the idea encourages extra memory bandwidth (but doesn't help
if you are looking for heroic core clock speeds).
When doesn't the feature work ?
If you buy a 2.8GHz/FSB800 processor, the "normal" multiplier
is 14x, the same as the "safe" value of 14x would be. In this
case, no power is saved, and there really isn't an option. For
that processor, the BIOS would be greyed out.
If a processor doesn't support that kind of feature, then that
would be another reason to grey out the BIOS. I think a PRB=1
processor, is the one that supports the two multiplier values.
Perhaps a 3.4GHz or a 3.6GHz processor, would be a good
candidate for "Lock Free", as those are pretty hot processors,
and might have PRB=1 set inside them.
"Lock Free" does not help you achieve a higher core speed. It
is intended to improve memory bandwidth, and must be used
in conjunction with adjusting the input clock to the CPU,
to higher values. Since, on your board, I don't even see a
BIOS entry that allows the CPU clock to be adjusted, the
"Lock Free" is pointless. A cruel joke if you will.
What other ways can you overclock ?
1) BSEL modding. If you were to adjust the BSEL code, to a
higher value, then the clock generator may be tricked into
giving out a higher clock. This is not a very practical
option on older motherboards, as BSEL is a two bit code
(two pins on the bottom of the processor), and not all
code points might be supported by the clockgen
chip. I believe it is possible that some of the more
recent processors have a 3 bit BSEL, and perhaps more
options (but I'd have to look that up and verify it).
BSEL modding gives such large jumps in frequency, to be
a pretty poor method of searching for a stable overclock.
Some of the recent Core2 processors, have pretty large
overclocking ranges, which is why for some of those, you
can fool around with BSEL.
2) Using an overclocking program in Windows. The "clockgen"
program from
www.cpuid.com is a popular example. But that
program has support for very few pieces of hardware, as each
case must be custom programmed. Thus, only certain motherboards
are handled, and the author of that program doesn't have all
day to sit around adding thousands of motherboards to the
supported list. There is a picture of the control panel here.
http://www.ixbt.com/short/2k6_soft/clockgen.png
The clockgen web page is currently not working, so you can see
what clock generator chips are supported, by looking at an
archived copy of the web site.
http://web.archive.org/web/20070406135941/http://www.cpuid.com/clockgen.php
Bottom line ? If you want an overclocking motherboard,
make sure it has the necessary BIOS settings first, before you
buy it. Motherboards are divided into catagories, according to
market and purpose. The cheapest ones are intended to be used in
business machines (office computers), where overclocking is not
an option. Thus, not one additional cent of expense is put into
making them overclockable. If you buy one of those motherboards,
then you might as well have bought yourself a Dell
If I missed something, and there really is a setting to change
the input clock to the processor, then you'll be overclocking
in no time. If, as the manual shows, there is no setting, then
you're stuck.
Paul
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