1333MHz RAM only shows as 664MHz?

[Roy_10]

I have 48gb of ram. 6 sets of 8gb DDR 3 1333 MHz / PC3-10600. Specific RAM chips are Samsung M393B1K70DH0-YH9. They're all identical.

But... I ran a program called Piriform Speccy and it's saying for RAM that I have 48.0GB Triple-Channel DDR3 @ 664MHZ (9-9-9-24)

Why are the chips good for 1333 MHz but the diagnostic tool says i'm only getting 664MHz out of them?

The computer is an HP Z600 with two Intel Xeon X5650 processors, motherboard is Hewlett-Packard 0B54h. I have a NVIDIA Quadro K620 graphics card.

 

[Tradesman1]

The DRAM is DDR (DOUBLE data rate) so it runs at true freq of 667 (+/-) with an effective data rate of 1333

 

[alexoiu]

Some programs like Speccy, or CPU-Z indicate half of speed (DDR - double data rate). Your memory runs as advertised, at 1333.

Edit: already answered.