Would this be an overclocked system?

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Athlon XP3000+ M CPU in an ASRock K7VT4A+. 512Mb PC2700 ram.

The default settings according to AMD is fsb=133MHz and a multiplier of 16

Would there be an advantage gained if I change the fsb to 166MHz and the
multiplier to 13 (2158MHz)? I believe this motherboard allows you to change
the multiplier settings. Could the increased fsb cause problems with the
other devices on the motherboard or does the motherboard automatically set
the correct dividers for the other components?

Thanks for your reply.
David Farber
L.A., CA

Re: Would this be an overclocked system?

David Farber wrote:
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Executive summary:

    Yes. There is an advantage. More FSB speed allows better memory transfer

There is no "lock" setting or discrete frequency setting ( AGP/PCI
66.66/33.33MHZ )
in your BIOS.

There are four frequencies of interest.

1) Clock feeding CPU.
2) Clock feeding memory (usually a ratio of simple integers, times CPU clock
3) Clock feeding PCI cards
4) Clock feeding AGP card.

3 & 4 tend to be related to one another (AGP = 2 * PCI), so I won't treat them
separately, and assume they are related by a factor of 2. If PCI is 37.5 MHz
(the max useful value with no danger), then AGP would be 75MHz. The standards
define AGP and PCI as 66.66MHz and 33.33MHz as nominal values. Values above 75MHz
for AGP, cause problems for cards more modern than ATI 9800Pro. Older cards,
can take clocks higher than that.

In the clock generator chip, for older technologies (where the BIOS doesn't show
a separate setting for AGP and PCI clocks), the PCI clock is derived from the
CPU clock. If CPU is 133Mhz, they use a divider of 4 inside the clock generator
chip. If CPU is 166MHz, they use a divider of 5. The "special" frequencies
of 133MHz and 166MHz, also happen to be the values selected by the processor

Intermediate frequencies may be selected manually in the BIOS. For example,
up the 133Mhz clock to 150MHz, gives 150/4 = 37.5MHz for PCI. Therefore, for
safety on an older motherboard, you avoid frequencies between 150 and 165MHz,
and the
next useful value is 166MHz (if it works). It means that while the BIOS may offer
a fine tuning option, there are still "zones" of frequencies to avoid. Corruption
of your disk drive may result if you violate the rule. (Which is why, if testing
for initial stability, I like to boot with a Knoppix CD in the CDROM drive. You
can't hurt a CD. Knoppix is a 700MB .ISO download from knopper.net and is a Linux
operating system.)

The memory clock settings in the BIOS, are not absolute frequencies as such. If
select 133MHz for memory, and the CPU is 133MHz as well, the design probably has
1:1 ratio between the two clock signals. If you then bump the CPU clock manually
to 150MHz, that should result in the memory overclocking by the same amount. A
memory at 150MHz, is running at DDR300. When the CPU clock is using one of the
values of 133MHz or 166MHz, it is also possible that the memory values will
again read correctly. (So, in a sense, "sane" ratios exist at the magic clock
values. Oddball values, which you can still adjust around, exist for intermediate
settings. You can observe how this works, by using a copy of CPUZ from cpuid.com
and make tiny changes, then observe the reported results in CPUZ.)

So, by all means, try the CPU jumper of 166MHz. Your RAM is PC2700 or DDR333,
and it
is a perfect fit for a DDR333 setting in the BIOS. The best transfer efficiency,
often when the CPU and memory on these systems, is at the 1:1 ratio. So if using
FSB266, then DDR266 might be good. (To do better on the memory, you might have to
go to DDR400 setting, to beat the latency disadvantage, with the clock rate
Add latency happens, when the memory bus samples need to be resynchonized to the
FSB interface.)

If using FSB333, then DDR333 might be good. Check that the multiplier setting
you need,
works properly while you are still at FSB266 or lower. If you are sure the
works properly, then switch up to FSB333 and try it. If the setting doesn't work,
try FSB266 jumper and DDR266 BIOS settings, then use the manual BIOS control to
from a CPU input clock of 133MHz, to 150MHz. 150MHz should be the next lowest
clock choice.

To see some of how the clock generator chip works, this is a sample datasheet.
This clock generator is a couple generations older than the one on your
You can see how the PCI clock is affected by the main clock choice here. The
on your motherboard, would go to the equivalent of the FS3,FS2,FS1,FS0 signals,
and helps to select a "magic" value for system startup.


There are many clock generators made by that company. To see how many, have
a look at this list.


And yes, these are all aspects of overclocking.


Re: Would this be an overclocked system?

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transfer speeds.
66.66/33.33MHZ )
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clock signal)
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above 75MHz
doesn't show
processor maker.
example, bumping
for maximum
165MHz, and the
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may offer
drive. You
a Linux
such. If you
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probably has a
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amount. A
the magic
DDR333, and it
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efficiency, is
have to
rate advantage.
to the
setting you need,
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doesn't work,
control to go
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lowest safe
The jumpers

I believe your executive summary really connected the dots for me. Let me
make sure I understand this though. As long as I pick one of the preset (is
that what you define as magic?) frequencies, the "frequencies of interest"
take care of themselves. The tricky part is what happens when you bump the
fsb speed a bit and all the other frequencies get bumped as well which is
why you need to know what frequencies to avoid.

I changed the fsb to 166, the multiplier to 13, and so far, the system is

Thanks for your reply.
David Farber
L.A., CA

Re: Would this be an overclocked system?

David Farber wrote:

Quoted text here. Click to load it

The set of frequencies defined by the processor manufacturer, all seem to be
a multiple of the PCI standard frequency. 133MHz, 166Mhz, and 200Mhz are
examples. They may have chosen those frequencies, so they could use a
simple divider to make PCI and AGP frequencies. They have other techniques
now, for creating PCI and AGP, which allows the PCI and AGP to be "locked".
So on more modern boards, you can dial the CPU clock in 1MHz increments,
without having to worry about PCI and AGP. The frequencies are no longer

But previous generations were not quite as flexible, and the PCI/AGP/memory
clocks floated along with the CPU clock. And that is why there are certain
CPU clock settings, which might not make the other bits of hardware happy.

One reason for corrupting a disk, is the PCI clock is used to derive a
clock for the IDE ribbon cable to the disk drive. If the IDE clock goes
too far out of spec, that corrupts data transfer to and from the drive.
Even SATA and PCI Express interfaces have issues like this, and there are
some SATA motherboards, where overclocking will corrupt SATA. Even more
recent clocking schemes, have fixed those kinds of issues, so that
SATA and PCI Express are locked (i.e. independent) as well.

If you changed to the CPU input to 166MHz (=FSB266), and set the multiplier
as you liked, and CPUZ verifies that all the resulting frequencies are
correct, you have nothing to worry about. Test with Orthos or Prime95 "torture
test", and verify that the machine is really stable. Just booting into
Windows is not a stability test. I put the Orthos link first here, simply
because the interface is a little easier to understand. Orthos will run more
than one thread for testing, and so Orthos can be used on dual core processors.

http://sp2004.fre3.com/beta/beta2.htm (Orthos tester)
http://www.mersenne.org/freesoft.htm (Prime95)

Prime95 was invented to find Prime Numbers, a mathematics thing. The torture
test option in the Prime95 program, was simply put there to verify that a
computer about to work on finding prime numbers, was working properly. No
sense verifying a prime number, with a computer that makes mistakes. Purely
as an accident, overclockers discovered the testing option, and the
Prime95 program became more popular because of that feature, than it
did in furthering the study of mathematics.


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