Q: Firmware update for MCP79 AHCI?
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Jan 22, 2016 6:01 PMby RRUZICKA,Your comment is not helpful and quite misguided.
MCP79 AHCI is from Nvidia which Apple included in the iMac. From reading the Intel forums and other SSD manufacturers, the issue is due to the NVIDA not properly negotiating the speed - as the Intel SSD is performing to spec.
The intel thread:
https://communities.intel.com/thread/28764?start=0&tstart=0
As the SSD is SATAIII (6Gb), it should negotiate down to SATAII (3Gb), but instead it defaults to SATAI (1.5Gb).
It appears that Apple does have more recent firmware on some the MCP79 in other Mac's (2010 Mac Mini supports AHCI 1.3), but not the 2009 iMac for some reason (support AHCI 1.2).
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Jan 22, 2016 7:35 PMby Mike Sombrio,Does the Intel SSD use a Sandforce or Marvell SATA controller? If so there's a conflict with 6Gb/s SSDs and the Nvidia MCP79 controller. Return the SSD and get one that does not use Sandforce or Marvell like a Crucial or Samsung. OWC can sell you a 3Gb SSD that will work fine also.
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Jan 23, 2016 10:02 AMby RRUZICKA,Thanks - I had read the same thing in the forums. However, then someone with a Mac Mini (2010) with the same MCP79 controller sent a screen shot showing the correct negotiated speed (3gb) with the same exact Intel SSD that I have (on the Intel forums). However, the MCP79 in the Mac Mini indicates that it supports AHCI 1.3 versus mine in the iMac which indicates it supports AHCI 1.2. Perhaps my only option is to return it but kind of a pain to crack open the iMac. Seems like the MCP79 in the iMac could support AHCI 1.3 like it does in the mini.
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Oct 8, 2016 10:27 AMby joyb2u,Late reply but, after EFI Boot ROM update, the chipset in my MacBookPro7,1 changed from MCP79 to MCP89. Samsung 830 SSD is negotiating at 3 Gb/s just fine. Somehow this update was not done automatically with software update. Download and run it manually from:
About EFI and SMC firmware updates for Intel-based Mac computers - Apple Support
See if it helps. Cheers!
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Oct 10, 2016 11:18 AMby Winoman Lime,HARDWARE: My iMac mid 2009 equipped with the NVidia MCP79 AHCI, is als showing that only 1.5GB (of the possible 3GB) connection speed is available.
I also have a new Samsung EVO 850 SSD installed the DVD slot. System Information shows that the SSD is connected to the SATA/SATA Express. So thats good i suppose. I did a clean install of Mac OSX 10.11.4 El Capitan, and that runs fine so far.
TEST: After testing the drive speed with Black Magic Disk Speed Test, i also experienced a slow performance. Somewhere around only 105MB/s. (So i was happy to find this recent answer!)
UPDATE: After downloading the right updater and activating it, the installer gave the reply "Your machine doesn't need this update".
CONCLUSION: So now i'm a little stuck here. Is there anything else i can try?
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Oct 15, 2016 1:52 PMby Winoman Lime,Hi joyb2u,
Thanks for your reaction.
Small update first, my iMac is Early 2009 (instead of mid-2009)
- This is the installer: IM91.008D.B08 (EFI 1.4)
- Model identifier is indeed iMac9,1
- AHCI Version 1.20 Supported
- TRIM is enabled after your response
After that i enabled TRIM (although im not sure what it does and wether its necessary. This also dd not give any speed boost.
Also i did the following:
I removed the SSD from my DVD bay, to the location of the original HD, whit a newer tech bracket.
I also discovered that on this Early 2009 model, the 3GBS SATA port is only enabled for 1,5GBS. I think that is the real bottleneck. I searched for "3GBS fix" but didn't find the right info.
i'm a little disappointed that my older 2007 iMac runs at 3GBS with the SSD right now and so performs even better than this more recent model ;-(
So please let me know if you can help me out some more ;-)
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Oct 16, 2016 12:46 AMby joyb2u,How did you enable TRIM? Did you confirm under System Information>SATA/SATA Express that TRIM is activated?
TRIM is an OS managed garbage collection (loose analogy to defragmentation on HDD). If you have some time, read the whole article Anand Lal Shimpi wrote 7 years ago that still explains very well what TRIM is http://www.anandtech.com/show/2829/8
You can try a different drive brand, e.g. Crucial. Read JDW1's experience with iMac9,1 and Samsung 850 Evo Best COMPATIBLE ssd for NVidia MCP79 chipset?
Why some MCP79 chipsets can only go as high as SATA I vs SATA II on other machines is a mystery that only Apple knows. My guess is that since iMac HDD is not officially user replaceable, they never bothered to provide firmware update to make the Nvidia chipset compatible with SSD's. My MacBookPro7,1 on the other hand, has officially user replaceable HDD and Apple provides official instructions how to do it. By the way, Samsung 830 negotiated at 3 Gb/s even with the previous Boot Rom Version on my MacBook, but named the chipset as MCP79, and after the update MCP89.
Since most of the files run by OS are in the 4K size range, you don't need high throughput, so even at SATA I speeds, SSD is still faster that HDD.
One last thing you can try, as suggested by asleb, who was recommended by Crucial rep
Since your drive is already in, and opening iMac is a pain (just to unplug SATA cable for 8 hours), here is a simpler solution: http://forum.crucial.com/t5/tkb/articleprintpage/tkb-id/ssd@tkb/article-id/84
Cheers!
