1066MHz RAM displayed as 400MHz RAM

Here's a text dump from CPU-Z. I've got 2 x 1GB of Transcend AXE RAM.

Why does it display itself as "PC2-6400 (400 MHz)"? I thought PC2-6400 was 800MHz, but this is specifically 1066MHz RAM...it's what it says on the box and the RAM modules.

What's going on?

 

Can you specify ram speed in the bios? Sometimes you can't sometimes you can (mine does). You may have some settings locked, set to lower settings, or maybe your mobo doesn't recognize the higher speed ram.
If it is running in dual channel mode, which you should have it in, then you will see the speed as roughly half of its advertised, since 800 mhz ram would run at 400mhz, but sends data in both directions (unlike ddr ram), which means that it is working at 400mhz x 2. Its a little hard to explain, maybe I'm just tired, but you should see half of the rated speed.

 

I'm aware that DDR2 RAM would be listed as 1/2 the usual speed, but mine should be listed at 533MHz, not 400MHz.

 

Did you read my first sentence?

The 2 different speeds show up in your post, both 400 and 533, so something isn't right.
Does your mobo support faster than pc6400?

 

It's a P35-DS4...it should. Says "1066MHz FSB" right on the front.