SSD RAID0 performance on HM67

Just got my DT780DX (HM67 chipset) with two 120Gb Intel 510's in RAID0. Naturally, the first thing I did was run CrystalDiskMark to see some insane numbers

However, I was somewhat puzzled when I saw about 550MB/s read and 400MB/s write speeds. Isn't that supposed to be a speed of a single 510? In that case, isn't RAID0 supposed to be closer to 800+MB/s?

Disclaimers:

1) I know that this performance is more than enough, and I am unlikely to see any difference in real-life performance. My question is about benching performance, just for the sake of the number.

2) I know that RAID0 doesn't scale to N*100% the speed of member drives, but I expect to see at least 150% of the single-drive performance. Let me know if I am mistaken.

 

Are you sure both drive bays are SATA3?

 

All laptops using the Sandy Bridge processors (i7-2xx0) have SATA III controllers for Ports 0 and 1, which is where the hard drives are connected. Ports 2 through 5 are SATA II, but that is where your optical drive and eSata port are connected.

I have the SSD drives on ports 0 and 1, and a regular HDD on the optical drive bay.

 

How do your numbers compare to something like this - Intel SSD 510 Series 120GB Review > Benchmarks: CrystalDiskMark 3.0 - TechSpot Reviews