bios vs boot memory speed

[artsci2]

My AMD Sempron 3400+ on a K8M800 chipset reports 800Mhz memory speed on boot but the bios reports 333hz (667) current memory clock.

The bios does report MaxMemClock selected and there is an option of 800Mhz that I have selected. However the lines above those settings show a current FSB of 200 and DRAM frequency of 333.

Is the memory running at 667 or 800?

Is this confusion a result of the older chipset running with the new CPU that has onchip memory controller? This is a NewEgg CPU combo deal.

[RealNC]

Run memtest86+ (install it from your distro's repositories and make a Grub entry for it if your distro doesn't do this automatically). It will tell you the real frequency (and timings) of your RAM.

The Grub entry looks like this:

title=Memtest86+
root (hd0,3)
kernel /boot/memtest86plus/memtest.bin

Adjust root and kernel as needed.

[artsci2]

Thanks RealNC,

Memtest86 version 2.01 was preinstalled in my Ubuntu 8.10 system

here's the result:

Sempron (0.09) 1800Mhz
L1 cache 128k 14753MB/s
L2 cache 256k 3515MB/s
Memory: 2047M 2068MB/s
Chipset AMD K8 (ECC disabled)
Settings:RAM : 450Mhz (DDR900) / CAS : 5-5-5-18 / DDR-2 (64 bits)

So cross checking with the speed reports gives 450x64/8=3600MB/s

and: 333MHz*64bits/8bits/byte= 2664MB/s

and: 2068MB/s / (64bits * 0.125bytes/bit) = 258.5Mhz

So does this mean I'm actually running mem at 266Mhz?
Where is the 450Mhz coming from?
I also tried selecting "auto" for memory speed in the bios and got the same results.
"load optimized defaults" in bios also gave identical results.

[RealNC]

Last test would be CPU-Z on Windows :P

[artsci2]

Maybe I'm looking at the wrong end of the memory throughput chain in the above calculations.

with the cpu at 18000Mhz on a single core can it use the full bandwidth of the DDR2 800 memory?

I bumped the FSB to 223Mhz and got Memtest86 results of:

Sempron 2007Mhz
L1 cache 128k 16447MB/s
L2 cache 256k 3919MB/s
Memory 2047M 2386MB/s
Settings RAM 501Mhz (DDR 1003) 5-5-5-18 DDR2 64bit

so it just made everything go faster with no conclusion about CPU vs memory bandwidth.....