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AHCI Question

Last response: in Storage
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February 21, 2011 9:51:09 PM

Hello,

I recently purchased an OCZ Vertex 2 50Gb SSD. Love it! However, after reading some various articles I keep reading about AHCI and making sure this was used during install. When I installed Windows 7 64bit I just followed the prompts and it installed (very fast I might add). My question is do I need to setup the AHCI? My system config is;

ASUS P5KPL-CM Motherboard with an e8400 cpu. When I go into the bios and look at the drive settings and other areas in the bios etc I see NOTHING about AHCI. Does every motherboard even support this or am I missing something? I just want to be sure I have it setup to get the most performance out of it that I should be getting. I mean its blazing fast compared to the SATA drive I had in there (it boots from POST to desktop in ~22 seconds! wow!)

Anyhow, anyhelp or advice appreciated!

Thanks,

More about : ahci question

February 21, 2011 11:29:08 PM

After doing a little Googling, it looks like your motherboard does not support AHCI. You don't need AHCI for you to use your SSD. All AHCI really does is enable SATA's advanced features such as hot swapping and native command queuing.
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a b G Storage
February 21, 2011 11:41:42 PM

You don’t need AHCI for a SSD disk as command queuing offers no advantage for a SSD drive and could in fact slightly slow it down, and would only be required if you wanted to hot swap the drives.
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February 21, 2011 11:48:03 PM

Wait, don't you need AHCI to enable TRIM, or can the OS use TRIM regardless of the controller setting?
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a b G Storage
February 22, 2011 12:14:52 AM

I forgot about TRIM, yes you do need to enable AHCI to enable TRIM and it must also be supported in the BIOS as well something that I don’t think the ASUS P5KPL-CM Motherboard does.
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a c 283 G Storage
February 22, 2011 3:43:52 AM

1. Your OCZ Vertex 2 ssd supports TRIM.

2. AHCI must be enabled in the motherboard BIOS in order for it to work. I checked the owner's manual for your motherboard. The BIOS is at least 4 years old and fairly simple. Check the Asus web site and Asus forum to find out if there is a BIOS update for your motherboard.

3. TRIM is a Windows function. By default TRIM is enabled. However, it is a good idea to check if TRIM is really working.

4. The Windows TRIM function allows Windows to tell a solid state drive which data blocks are no longer in use (such as those left by deleted files) and can be wiped. The ssd uses that information for garbage collection (wiping data blocks).

5. An ssd that supports TRIM can collect garbage/wipe without TRIM but it "might" not be as efficient. Efficiency levels can vary by ssd brand, model and configuration. It can also vary depending on how an individual uses a computer.

6. There are ssd's that do not support the Windows TRIM function. The ssd's simply rely on garbage collection.

7. The OCZ web site and the OCZ forums have intructions for installing OCZ ssd's and settings that need to be adjusted.
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February 22, 2011 3:54:04 AM

pjmelect said:
You don’t need AHCI for a SSD disk as command queuing offers no advantage for a SSD drive and could in fact slightly slow it down, and would only be required if you wanted to hot swap the drives.


I would like to disagree here. Take the latest article from Toms: http://www.tomshardware.com/reviews/ocz-vertex-2-25nm-s...

It seems like SSD's really like a higher queue depth.

From Wikipedia:

"NCQ in Solid-State Drives

NCQ is also used in newer solid-state drives where the drive encounters latency on the host, rather than the other way around. For example, Intel's X25-E Extreme solid-state drive uses NCQ to ensure that the drive has commands to process while the host system is busy processing CPU tasks. [3]
NCQ also enables the SSD controller to complete commands concurrently (or partly concurrently, for example using pipelines) where the internal organisation of the device enables such processing.
For example, the SandForce 1200[4] based OCZ Vertex II 50GB drive running on a Dell Perc 5i (which doesn't support SATA NCQ) delivers about 7,000 4k IOPS (50% write) at a controller queue depth of 32 IOs. Moving the drive to the similar Dell Perc 6i increases this to over 14,000 IOPS on the same basis."


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a b G Storage
February 22, 2011 6:26:55 AM

I still don’t see how NCQ helps SSD drives it was after all designed to minimize head movement of hard drives I would have thought that it would increase the processing load on the host computer as it tried to work out the optimal head travel. TRIM on the other hand could speed up writes to the SSD.
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February 22, 2011 11:08:41 AM

Thanks very much! This is great information. Booo about my motherboard being older (I did know it was a failry simple board, perhaps an upgrade is imminent) I am running the latest BIOS, so it looks like AHCI is out of the question for me. I did find a post regarding TRIM and when I ran the below command it did come back as being enabled, so I *think* I'm ok there.

<quote>
The Trim command should be enabled by default on Windows 7, but if you want to check to make sure do this:


Command prompt > fsutil behavior query disabledeletenotify

DisableDeleteNotify = 1 (Windows TRIM commands are disabled)
DisableDeleteNotify = 0 (Windows TRIM commands are enabled)
</quote>

Thanks again for the replies, much appreciated!
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