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SATA mode and SSD drives


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definitely not imperative.

i can vouch first hand having just installed my first SSD about 3 weeks ago on an old mobo that didn't have 6gig SATA ports(only 3gig) and i stupidly forgot to set AHCI before installing Win7 so I've missed the NCQ boost.


the thing still rocks over the HDD but could be so much better.

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There is much information upon SSD from OCZ here



AHCI is recommended for faster operation of an SSD,

I have seen opinions that TRIM might still work if you choose to avoid AHCI mode.

but updating the firmware and issuing a Secure ATA Erase might require AHCI.


Whatever is good for OCZ is possibly not good for other brands.

It would be better to ask your question at a forum dedicated to your particular brand and model of SSD.

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  • 2 weeks later...

I believe the operation of NCQ actually PREVENTS the use of TRIM for an SSD,

I have just found in the following :-


An additional problem is that the TRIM command comes with a penalty. Modern SSD drives are parallelized devices that allow performing multiple operations in parallel. In order to get peak efficiency, multiple concurrent requests have to be sent to the drive. This happens via a Native Command Queuing protocol (or NCQ). Modern drives can run up to 31 commands concurrently and often achieve peak performance when there are close to 31 commands in the pipeline. The problem with TRIM is that on many interfaces it requires stalling the NCQ pipeline. That is, when a TRIM command is issued, all 31 commands must be finished while no other commands can go in. Then the TRIM command goes into the drive, and then the pipeline of traditional read and write commands accumulates again.


I believe NCQ is quite irrelevant to an SSD.

NCQ merely allows concurrent actions upon pending requests that are issued to a drive which can process in any order that the drive firmware considers optimal, e.g.

by minimizing alternate excursions between the inner and outer tracks,

and acting upon file clusters in the order in which they travel under the read/write head rather than the order in which user applications have issued file updates.


The SSD firmware may have reasons for altering the order in which it executes pending requests,

but seek delays between tracks and rotational order of cluster is the least of its concerns :rolleyes:




Windows 7's AHCI enables not only NCQ but also TRIM support on SSD drives (with their supporting firmware).


I believe the important thing for an SSD is not NCQ but AHCI, which is required for a "Secure ATA Erase",

which is a special process that in a few seconds will SIMULTANEOUSLY erase all cells.

( I remember more than 30 years agao it took half an hour of a powerful Ultraviolet Light shining through a Quartz Window to achieve the same effect on a few KiloBytes of Erasible PROM.)

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Well, I swapped IDE <-> AHCI modes again. So far, no issues at all (even when burning multisession with NERO). Fingers crossed.


I have in mind getting a SSD drive sometime in the future.


EDIT: I have noticed a lot of stuttering playing L4D2. I must investigate this.

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After some benchmarking on two different AMD systems, I have found out I prefer IDE native mode over AHCI. My reasons are:


1. I don't have any SSD so TRIM isn't needed.

2. I don't plan on using hot-plugging

3. NCQ doesn't give me any benefits (it seems meant for servers)

4. HD Tune benchmarks show IDE performance is better.


The two AMD systems are one Gigabyte (SB600 chipset) and one ASUS (nForce 720a MCP chipset). I guess Intel's AHCI is probably better but your mileage may vary.


Also, I have read that some (or many) optical drives just HATE AHCI.

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I have read somewhere that NCQ might incur in a small speed penalty or delay while sorting read/write operations sent to the queue.


I also have an i7 running on a Z68 chipset that is configured for AHCI. I have not even bothered to look into bios to see if it can be changed. The HDD performance is very good right now.

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