That's all correct, 3079MHz = 219MHz fsb * 2/3 mem ratio = 146MHz on the
RAM. But not optimal, which is why you should OC manually and not use
the AI thing.
There is a table in the manual that looks like this:
CPU FSB DDR DIMM Type Memory Frequency
800 MHz PC3200/PC2700*/PC2100 400/333*/266 MHz
533 MHz PC2700/PC2100 333/266 MHz
400 MHz PC2100 266 MHz
*When using 800MHz CPU FSB, PC2700 DDR DIMMs may run only at
320MHz (not 333MHz) due to chipset limitation.
For some reason, your PC3200 memory is being run at 266MHz (that is
a clock rate of 133MHz x 2). The AI Overclock is then simply bumping
the main clock that feeds both the processor and memory by 10%. That
is where the weird 146.7 is coming from. So, the question is, why did
the BIOS decide your DDR400 memory should be run at DDR266 ?
To start with, I would recommend verifying the system under nominal
conditions. Make the processor run at 2.8GHz/800 and check that the
memory is set to PC3200 = DDR400 = 200MHz memory clock. Get a copy
of memtest86 from memtest86.com - this program will prepare a bootable
floppy disk for you, or if you don't have a floppy, there is an ISO
CDROM image available as well. Test the memory and verify it is
error free in an overnight test.
When you want to overclock, consider this - at FSB800, your ram is
already running at its rated speed of DDR400. If you speed up the
processor by 10%, you would be running the memory at DDR440, which
might work if you increase the CAS memory timing one or more notches.
To keep the memory within spec, another thing you can do is to run
FSB800 and set the memory to DDR333. Then, as you increase the FSB
setting, the memory frequency gets increased as well. Since the
actual frequency in hardware is DDR320, you can overclock by 25%,
before the memory frequency has risen enough to get to the spec
limit of DDR400 again.
The BIOS choice of running the memory at DDR266 is way too conservative.
It suggests you may have attempted a much higher overclock, and the
BIOS responded by cranking the memory as low as it could go, in an
attempt to keep the memory in spec.
The nice thing about these boards, is they have memory divider settings
that allow the memory to be kept in spec while you are overclocking
the processor. You can even buy PC4000 memory, run CPU:memory "1:1",
and end up at FSB1000 with DDR500 memory. (FSB = cpu_clock x 4,
DDR = memory_clock x 2 ...)
I've read various comments on PAM, and as far as I know, the Intel
optimization only works at exactly FSB800. A BIOS that honors the
Intel information will disable PAM if you are overclocking. The
chipset timing has to be guaranteed at some set of conditions by
Intel, in order for this optimization to work. In principle, PAM
should work at FSB800 or less, but for some reason a BIOS will only
enable it at exactly FSB800.
This document is the best background info I've found from Intel
concerning memory usage with the 875/865 chipsets:
ftp://download.intel.com/design/chipsets/applnots/25273001.pdf
HTH,
Paul
