Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <_fSdnT487fdKjtLfRVn-pA@golden.net>, "Ken'" <kft34@golden.net> wrote:
> Paul
> I downloaded Prime 95 and run it on my present system a P4C800 E deluxe with
> a 2.8 Prescott with two sticks of OCZ PC4000 DDR EL Dual Channel memory.
> I ran it on my system non- overclocked and it ran overnight error free.
> I then overclocked it 10% and re-ran it and I get the error " FATAL ERROR:
> Rounding was 0.5, expected less than 0.4
> Hardware failure detected, consult stress.txt file."
> Could you please explain to me what I need to do?
> Thanks
> Ken'
>
> PS Mem test 86 runs error free.
First of all, don't use the automatic overclocking feature, unless
you at least use CPUZ to verify what the BIOS is doing to the
board. (
http://www.cpuid.com/cpuz.php )
Since the multiplier is locked on Intel processors, you can use
the FSB to overclock the processor. The normal settings involve
feeding 200MHz clock to the CPU, and the data transfer rate
on the front side bus is quadrupled to FSB800. The DDR ram
transfers data twice per 200Mhz clock, and that is a DDR400
transfer rate.
The memory bus has some dividers available, to run the
RAM slower than normal. At FSB800/DDR400, the divider is
terms "1:1". Some other available ratios are 5:4 and
3:2 (slower and slowest).
You can do a processor test first. By setting the memory ratio
to 3:2, the ram will run a lot slower than normal. That should
take the pressure off the memory. You can then lift the FSB
and test the processor. As the processor frequency rises,
the processor will need a bit more voltage. Your 2.8 might
be able to run at 3.5Ghz, with a little coaxing.
Once the processor is adjusted, you can start working on
the memory. By switching from "3:2" ratio to "5:4", that
will increase the memory bus speed, without changing the
processor core. Finally, if you use "1:1", that results
in the memory running as fast as the motherboard can manage,
with that choice of clock for the FSB.
I believe that the P4C800 and P4P800 family differ
slightly, in how the BIOS represents the ratio issue. The
P4P800 shows true memory speed, while the P4C800 numbers
are more representative of the ratio involved, but not
the true speed. The P4P800 SE, for example, offers to set
the RAM to 533MHz, according to the manual. But the options
offered are likely to be related to the current choice for
the processor clock.
On the P4C800, it should show DDR400, DDR333, and DDR266 as
options. These correspond to 1:1, 5:4, and 3:2 ratio. In
other words, the speeds are not true speeds, and instead are
a rough indication of the dividers available.
With your RAM, anything should be possible.
Set... Select... Gives...
(Normal) Clock=200 FSB= FSB800 Ratio=1:1 gives Memory=DDR400
Clock=250 FSB=FSB1000 Ratio=1:1 gives Memory=DDR500
Clock=250 FSB=FSB1000 Ratio=5:4 gives Memory=DDR400
Clock=250 FSB=FSB1000 Ratio=3:2 gives Memory=DDR333
^ ^
|___ x 2 for DDR x 2/3 = _____________________|
Using the bottom set of conditions, places the least stress on
the memory, and allows you to work on the processor. If you
use the 1:1 ratio (second line down in the table), that pushes
your RAM to its stated limit of PC4000.
For your memory to run at PC4000, it needs a Vdimm of greater
than the nominal 2.5V . You should check the oxztechnology.com
web site, to get the exact specs for your memory. Perhaps
2.7 or 2.75V would be a good starting point for testing.
So, start with the bottom line in the table above, as
that puts the least stress on the memory and allows you
to test what are the limits for your processor. In
terms of the Vcore voltage to apply to the processor,
I used to use:
http://www.cpudatabase.com/index.cfm?Action=search
but no new results have been added to the database for
a while, after some people submitted a bunch of bogus
overclocking results and messed up the database. I
don't see any Prescott results to go by. If I download
the processor datasheet, like this one:
ftp://download.intel.com/design/Pentium4/datashts/30056103.pdf
the absolute maximum voltage listed for the Prescott is
1.55V, so I wouldn't set the BIOS to more than 1.50V based
on that limit. Try bumping up the Vcore a bit, from whatever
the nominal value is, then increase the processor clock,
while the memory is set to "DDR266" (the 3:2 ratio). Perhaps
then, Prime95 will not error out.
If you plot some of the results from the cpudatabase
web page, and prepare a scatter plot in Excel, you'll see
at least a 500MHz spread on overclocking results, at a
given voltage. That means overclocking comes with
no guarantees.
Another setting you should adjust, is change the AGP/PCI
clock setting from [Auto] to [66.66/33.33]. This setting
prevents the BIOS from accidently overclocking the hub
clock that feeds the Northbridge. Overclocking the core
logic of the Northbridge is not necessary, in your quest
for a high overclock.
My overclocking conditions above would be considered to be
pretty conservative, so if you wish to live on the wild
side, consult the private forums for more info. Abxzone,
xtremesystems, pcper.com, etc.
HTH,
Paul
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