The problem could be, that the memory speed and the processor
FSB are mismatched. Now, a properly designed chipset should handle
a wide range of combinations, but it is a tough thing to design for.
The Nforce2, for example, has a bug in it, that is triggered by
running memory and CPU bus at different clock rates, so it is
a possibility.
Your processor is FSB533. This is a basic clock of 133MHz*4,
as four chunks of data are passed per clock cycle. To match this,
two channels of memory, running at 133MHz*2 (DDR is two chunks
of data per clock) is a perfect fit. If you have set the memory
to some "Auto" mode or "By SPD" mode, then the BIOS will pick up
on the fact that the memory is capable of DDR400 and try to set
the memory to that speed. As I said, with well designed chips,
any rate mismatch should work, but it doesn't always turn out
that way.
First of all, you need to get yourself a Windows utility. This
will allow you to independently verify that the BIOS settings
you are using, are actually working. Sometimes, when a BIOS is
first released, the memory control code isn't finished, and
the memory is fed fixed values. Using a Windows program allows
you to snoop on what is really happening -
http://pcextreme.net/reviews/xms3700/cpuz-max3.jpg
http://www.cpuid.com/cpuz
Due to the fact your chipset is relatively new, not all
utilities support the ATI chipset yet. You may have to
"shop around", to find one that is updated. The former
AIDA32 (now Everest and still free) might also work:
http://www.lavalys.com/index.php?page=product&view=1&subpage=3
When the BIOS displays 3-4-4-8, those are "teaser" numbers, and
those particular numbers are the most relaxed numbers possible.
Those numbers are typically used for PC4000 overclocker memory,
to make the memory work.
Your Crucial memory is manufactured by Micron, as Micron owns
Crucial and Crucial is the retail arm. While Crucial might tell
you the memory is CAS3, Micron's datasheets give all the specs.
If you look at the DIMM, you might see both a Crucial and a
Micron sticky label. You can use the Micron label to look up the
datasheet. Here is a sample sheet for memory with -40B in the
part number - this is DDR400 5ns memory, and the datasheet says
it is 3-3-3 memory. With some luck, you might find the CPUZ
display reflecting those numbers, if the BIOS has used DDR400.
http://download.micron.com/pdf/datasheets/modules/ddr/DDA16C32_64_128x64AG.pdf
The 3-3-3 numbers, when converted to time, is 3*5ns, where the 5
nanoseconds comes from inverting the clock rate of 200MHz. If
you set the memory to DDR266, instead of DDR400, you can improve
the numbers on the memory. DDR266 is 133MHz, or 7.5ns. At DDR266,
your memory can be run at 2-2-2. (The CAS number is fractional,
as in 1.5, 2, 2.5, while the other two numbers are integers, and
in this case, the product of the number times the clock period
must be greater than or equal to that 15ns number.)
I know all of this is confusing, so to start, change the memory
clock to DDR266, and see if it settles down. If the motherboard
has a Vdimm adjustment, it should be set to 2.6V for PC3200
memory, as PC3200 uses 2.6V while lesser memories use 2.5V.
Anything up to 2.75 or 2.8 volts or so is reasonable.
As for your choice of processors, I think you should have spent
a few more bucks and avoided the Prescotts as well. Prescotts
are power hogs, and will heat your room up.
A 2.4A 533 1MB Prescott is $124 at Newegg and uses 89Watts
A 2.4B 533 512KB Northwood is $148 at Newegg and uses 59.8Watts.
A 2.4C 800 512KB Northwood is $169 at Newegg and uses 66.2Watts
(supports hyperthreading if you have an OS that can use it -
disabling HT reduces the power closer to the level of the 2.4B)
The 2.4C will nicely match two DDR400 rams and allow you to
run them synchronously and get your money's worth from the ram.
You could try overclocking the other processors, because
especially in the case of the Prescott, there is no reason to
expect it won't do FSB800 (but, of course, the Prescott will
give you a collossal cooling problem). The FSB533 Northwood
might make it to FSB640, but I'm not sure whether a recent
stepping has the ability to make it all the way to FSB800 or
not. (
http://www.cpudatabase.com/CPUdb shows FSB710 is possible
with air cooling and reasonable voltages - higher needs exotic
cooling.)
Tell us how it works out. I see the ATI chipset is being used
in a lot of small systems, and for all these companies to use
the chipset, it must be demonstrated to work for them.
BTW - if you get stuck after adjusting memory timing, if you
see any messages about corrupted BIOS and the like, DON'T
listen to the prompts that suggest reflashing the BIOS. The
BIOS is not really corrupted. The Asus overclocking recovery
code doesn't work worth a damn, and all you really need to do
to escape from messed up settings, is the "clear CMOS" procedure
listed in the manual. Always remember to unplug the computer
before doing it, and wait 30 seconds for the ATX power supply
to discharge, before moving the CMOS jumper. Failure to do so,
will damage a tiny dual diode on the motherboard.
HTH,
Paul
