Retina 5K Flash Speed Weirdness

[MrGimper]

I have an iMac Retina 5K i7 with 1TB flash. I also have a 13" 2014 Retina MBP i5 2.8 with 1TB flash.

Both machines are fitted with the APPLE SSD SM1024F.

When I run Black Magic on my iMac I get write of ~680 and read of ~720

When I run it on the MBP I get write of ~900 and read of ~980

The only difference is that I have FileVault enabled on the MBP, but I would have thought, if anything, that would make the MBP slower

Why the big difference in speeds?

 

[hfg]

The RiMac is only 2 PCI lanes for the SSD, your rMBPro might be 4 lanes (as is the SSD part). They apparently didn't have enough PCI lanes for the iMac to do it right without dropping something else.

 

[yjchua95]

I have an iMac Retina 5K i7 with 1TB flash. I also have a 13" 2014 Retina MBP i5 2.8 with 1TB flash.

Both machines are fitted with the APPLE SSD SM1024F.

When I run Black Magic on my iMac I get write of ~680 and read of ~720

When I run it on the MBP I get write of ~900 and read of ~980

The only difference is that I have FileVault enabled on the MBP, but I would have thought, if anything, that would make the MBP slower

Why the big difference in speeds?

The iMac only has 2 PCIe lanes for the SSD, while the rMBP has 4 PCIe lanes available.

The reason is because the iMac has an extra two USB ports plus an RJ-45 Ethernet port, and these two have taken up two PCIe lanes on its own. So there's only two lanes remaining for the SSD.

Personally, I wouldn't mind a small sacrifice in speed in return for two more USB ports and the RJ-45 Ethernet port.

 

[MrGimper]

Thanks for the replies. At least I know there isn't an issue.