Maybe I must give more infos to the system I'm using:
macbook unibody mid 2009, I have installed windows 7 as standalone on an ssd, by standalone I mean I'm not using bootcamp from within MacOSX, but I'm doing a clean install of windows 7 on the ssd and then I complete the installation of the drivers with bootcamp, now my ssd is running in IDE mode, so how do I switch it to AHCI mode.
I hope I get from apple some acceptable answers for the following issues:
1. what driver do I have to use? giving my macbook has an nvidia chipset, is this driver part of bootcamp? and if yes where is it on the snow leopard DVD?
2. On a pc, AHCI is tweaked in the bios and registry, now how do I set it in my macbook ?
3. is this faisable or apple think that customers wanting to use a macbook with windows(mostly for development) don't need AHCI ?
Thanks for precise answers.
@The hatter
Before I post this forum I tried only changing the registry key but unfortunatly it failed, but let's forget about windows 7, even for Vista I think that's not faisable, my macbook is telling me that the serial-ATA is NVidia MCP79 AHCI, also supporting version 1.20 but under snowleopard, now where I find a driver for windows Vista, for a macbook and NO mac pro.
When you boot Windows/Linux/etc in Boot Camp, the disk controller is switched to IDE mode. This is done to enable Windows etc to be installed out of the box, i.e not needing any disk controller drivers to do so. In the case of Windows Vista and Windows 7, this is not much of a problem, since they both support USB drives for driver installation. However this is impossible for the Windows XP install process, due to it only supporting floppy drives, and by that I don't mean USB floppy drives. The floppy drive has to be internally connected to a floppy disk controller.
In order to make use of AHCI in your boot camp operating system, you will need an operating system loader such as the free grub boot loader, with modified code to switch your disk controller back to AHCI mode.
There is a patch to allow the 2008 Mac Pros (I think), and the latest MacBook/MacBook Pro notebooks prior to the introduction of the unibody series to be switched back to AHCI mode when you use grub. I personally use this patch with Ubuntu Jaunty and grub, allowing me to get the full disk performance from my controller on my MBP 4,1. However, this does not help NVIDIA chipset users.
In order to make such a patch, you need to find documentation on the disk controller in question, and look up how to switch it to AHCI mode. Then you need to modify grub's assembler code to make this change to the disk controller.
I apologise if I have lost some readers with the technical nature of this post, however there is no simple solution to this problem.
Thanks for explaining technical background of the problem.
BTW do you (or anyone here) know of any reasons why AHCI with NCQ enabled on modern drives might give worse performance than IDE mode? I've read some 2-year old posts on some forum mentioning NCQ penalty for desktop usage, but I found no real information to back them up.
NCQ replaced the queue method used by SCSI but benefits to most desktop systems is limited. Check StorageReview. It also isn't as "deep" a queue either.
But I think today just a small factor, more esoteric, and perhaps drives and firmware have improved. Even SSDs depend on using larger caches to improve their performance. Always something.
I found StorageReview article, a bit old but still has its points about queue length. Maybe missing AHCI in Windows on a workstation is not really something to cry about.
I've spent an entire evening trying to get AHCI to work on a macbook pro with the nvidia MCP79 SATA chipset. I have a OCZ Vertex 64gb SSD so i really like to get AHCI working because the small-file and multitask performance of this disk is half or less of what it should be in ATA mode.
Especially with a bit of multitasking windows really crawls to a halt.
Unfortunately there does not appear to be a solution. For the Mac Pro there is one, where you can patch the MBR which runs a few instructions to flip its Intel Sata controller back in AHCI mode. However for the nVidia chip in all the new unibody macbooks this is unknown. Even the linux guys don't know, and also don't seem to need it because their driver can apparently 'force' ahci and can live without the bios turning it on.
It is possible to force windows to load the Standard AHCI 1.0 driver, but that will not make it recognise the disks as AHCI disks so even though it looks like you have AHCI you still don't.
The only possible solutions are: Someone figures out an MBR patch to switch the nvidia controller to AHCI mode, or apple actually fixes this problem properly in its EFI bios to stay in AHCI mode before booting windows (adding a setting somewhere in bootcamp).
I really hope this problem gets fixed because Windows performance is essentially destroyed compared to any other brand of laptop with similar specs.
If there is a solution for the Mac Pro I REALLY would like to know how it's done, preferably in a step by step instruction (something like 'patch the MBR to flip the Intel SATA controller back to AHCI' isn't going to do it for me unfortunately). Thanks in advance for your help.
