Hi, today I bought the new Imac 5K and I love it! It came with the 8 GB 1867-MHz DDR3 RAM. In an official Apple retail store (Belgium) I asked them to add another 16GB. They did add the 16GB, but they put in 1600-MHz DDR3 RAM instead of the 1867-Mhz RAM already installed. They said it wouldn't make any difference in speed and also that it would not give any conflicts. They also said that at the moment they couldn't get the 1867 Mhz. When I go to check 'about this Mac', it says that I have 24 GB of 1600 Mhz DDR3 RAM... (doesn't mention the 1867 Mhz RAM). The only issue I have is that when I start the computer, after about a third of the process bar in the log in screen, the machine blinks, the log in screen disappears to come back a second later and then the process bar continues and I can log in fine. I must say that I used a terminal command not to hear the start up sound. Will this difference in clocktime (MHz) make a difference in speed? Will I get issues with my computer due to this? I contacted Apple support and they said that it wouldn't make a difference. Can anyone please give some advice?