I've got a
Mac Pro 4,1.
I had two
KVR1066D3Q8R7S/8G planks in it and it ran on 1066 Mhz.
Now I've bought two planks of KVR1066D3Q8R7S/8GI (the same with "I" at the end - stands for intel certification). I've got 32 Gbs, but the system says they run at 800Mhz.
Why? Is there a way to fix it? Is it because I use four slots instead of a triple setup? Will 3x8Gbs perfom better than 4x8 or is it better to have more RAM?
UPD1: If I use either three of the sticks, they all run on 1066, when i insert the fourth one, everything drops to 800 Mhz.
UPD2: That's what I have found here:
Single-processor computers have four memory slots. Depending on the model, you can install 1 GB, 2 GB DIMMs, or 4 GB DIMMs. The processor’s memory controller has three memory channels. DIMM slots 1 and 2 have their own channels; slots 3 and 4 share a channel. For optimal memory bandwidth, all three memory channels should be used, and memory should be balanced across the three channels.
Note: Populating slot 4 slightly drops maximum memory bandwidth, but depending on the applications used, overall system performance may benefit from the larger amount of memory.
But it is still confusing. I thought the bandwidth that is being described is overall bandwidth not like all chips are dropping to 800 Mhz...