Mac Pro Hard Drive speed question


macrumors newbie
Original poster
Feb 14, 2011
I have an MB871LL/A which is also 4,1. Its a 2009 Quad Core Nehalem model.

Here is the dilemma, Sata 2 or Sata 3?

I have received all sorts of answers from everyone including Apple Care.

Should I get a Sata 2 or Sata 3 drive? The manual says the computer runs Sata 2. Western Digital makes a Sata 3 whcih of course is 6 gb/s of transfer for a higher price.

Again I have received many variations to this question. The bottom line question is this: Can I get the full benefit from a Sata 3 drive at double the transfer speed just by installing the drive?

Apple claims I'm wasting my money because the machine will run it but it will drop it down to Sata 2 speeds 3 gb/s. Others claim if I get a card for one of the open slots and connect the drive to the card, it will run at Sata 3 speeds.

Can please give me the real answer?

PS: Apple tech support should be humiliated with their various responses thus far and I'm shocked they cant even answer an easy question like this!!



macrumors 65816
Aug 11, 2009
Theoretical maximum transfer speeds:
  • SATA 2 3Gbit/s: 375MB/s
  • SATA 3 6Gbit/s: 750MB/s

  • Mechanical drives: SATA 2 drives are sufficient on both SATA 2 and SATA 3 ports, as there are no mechanical drives that exceed 375MB/s read or write speed.
  • SSDs: SATA 3 drives can saturate SATA 2 ports better than SATA 2 drives; SATA 3 drives benefit from SATA 3 ports, too, as their transfer speeds can be higher than the maximum theoretical transfer speed of SATA 2.


macrumors 65816
Nov 15, 2010
Edinburgh, UK
If you plug any HDD or SSD into the drive sleds they are limited to SATA2.

If you buy a PCI SATA3 card into an expansion slot you can use SATA3 drives but I don't think you can use it for a boot drive. Check the forums here for "SATA3 card" threads.


macrumors G4
May 6, 2008
Real world thoughputs:
  • SATA II = ~275MB/s (losses namely due to 8b/10b encoding)
  • SATA III - ~540 - 550MB/s
As mentioned however, mechanical disks, including the newer 6.0Gb/s compliant models, can't even saturate SATA II's real world throughputs, so if you're using mechanical disks (yes, it will "drop" to SATA II, but it's not an issue with mechanical disks), you don't need to bother with a PCIe SATA III card.

Now if you want to run newer SSD's (those that can exceed 275MB/s sustained read/writes), then a SATA III card would need to be added in order to get all the performance such a drive can deliver. Such cards can be had inexpensively (and a couple have even been discovered that will boot OS X in single disk mode under OS X).
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