C/F cards reading speeds

[blue marlin]

i post this in the sports section as 95% of my stuff is sport
i am not a techno expert so want opinions/info on the following i use 2 1d mk4 bodies one on a 400 and one on a70/200 used with 3 identical sandisk cards why does one card read faster than the other into the mac?
also i add that both bodies are set up the same.
its not a problem just that i wondered why.

 

[Photodiva]

Is one card older than the other? Do they have different speeds? I bought a new card reader recently and that speeded up the process too.

 

[pope]

Is the slow one, a fake card??

 

[photoSheikh]

I had a dodgy card from eBay that came with a camera. It actually reported a different size than my other 8gb CF cards and it wasreally slow. It went in the bin after I took it apart. There are CF Card speed test software out there on the web.