AHCI - Why is it Considered So Much Better Than IDE?

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RhoXS

Senior member
Aug 14, 2010
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Until a few days ago, I was using an IDE interfacing with my G2 SSD. The time from the instant "Starting Windows" (W7) appeared to a completed Desktop was consistently 17.8 seconds. Most applications started instantly. One application, Paperport, started with a couple second or so delay but even this was incredibly faster than the time it took with a HDD.

I happened to recently read some stuff extolling the virtues of AHCI, so I switched to AHCI a few days ago. Using the same starting and stopping points, the W7 start up time increased to almost 24 seconds. I was unable to notice any other change, good or bad, with respect to Apps starting and databases loading. Therefore, I reverted back to the seemingly faster IDE interface.

So, why do so many people think that using an AHCI interface, in lieu of IDE, is so much better? I even saw one posting were the writer stated he did not think an SSD would work with anything other than AHCI. What am I missing by continuing to use IDE?
 
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dorion

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Jun 12, 2006
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AHCI allows SSDs to use the Trim command. If the Trim command is used long term SSD performance degradation, due to internal fragmentation, is minimized.

Also NCQ is available to HHDs on AHCI allowing for some speed increases.

On the change in speed you should try the Intel AHCI drivers, I've heard they are loads better than the built-in W7 ones.
 
(sic)Klown12

(sic)Klown12

Senior member
Nov 27, 2010
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TRIM works in IDE mode with a compatible driver(the built in Windows driver is preferred) in Windows 7. AHCI's main advantages compared to IDE is the ability to Hot-Swap(self-explanatory) and NCQ(can increase performance in situations with heavy multi-tasking). If you don't need either of those, then sticking to IDE since it's faster for your build is the smart thing to do.
 
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V

Voo

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Feb 27, 2009
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(sic)Klown12 said:
TRIM works in IDE mode with a compatible driver(the built in Windows driver is preferred) in Windows 7. AHCI's main advantages compared to IDE is the ability to Hot-Swap(self-explanatory) and NCQ(can increase performance in situations with heavy multi-tasking). If you don't need either of those, then sticking to IDE since it's faster for your build is the smart thing to do.
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Yup, yup and yup.

Although I find it rare that using AHCI increases your boot time that much - maybe a BIOS update would help there.
 
fffblackmage

fffblackmage

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Dec 28, 2007
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Voo said:
Yup, yup and yup.

Although I find it rare that using AHCI increases your boot time that much - maybe a BIOS update would help there.
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From what I've heard from someone else on this forum, AHCI might actually increase boot-time.
 
V

Voo

Golden Member
Feb 27, 2009
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fffblackmage said:
From what I've heard from someone else on this forum, AHCI might actually increase boot-time.
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Why would it? It has a minimal higher overhead and probably takes a few ms more to initialize, but certainly not 24seconds - that's clearly some kind of bug, probably some communications mismatch that times out.
 
(sic)Klown12

(sic)Klown12

Senior member
Nov 27, 2010
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Voo said:
Why would it? It has a minimal higher overhead and probably takes a few ms more to initialize, but certainly not 24seconds - that's clearly some kind of bug, probably some communications mismatch that times out.
Click to expand...

When I use AHCI and had the older(pre-TRIM support) AMD AHCI driver, during boot up it would poll my Blu-Ray drive which added an additional 10 or seconds to boot up. I never could figure out why it did that and then suddenly stopped with the 10.11 AHCI drivers.
 
VirtualLarry

VirtualLarry

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Aug 25, 2001
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(sic)Klown12 said:
When I use AHCI and had the older(pre-TRIM support) AMD AHCI driver, during boot up it would poll my Blu-Ray drive which added an additional 10 or seconds to boot up. I never could figure out why it did that and then suddenly stopped with the 10.11 AHCI drivers.
Click to expand...

Isn't that around the time that installing those newer AMD drivers, actually uninstalled AMD's AHCI disk driver, and replaced it with MSAHCI.SYS?
 
(sic)Klown12

(sic)Klown12

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Nov 27, 2010
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VirtualLarry said:
Isn't that around the time that installing those newer AMD drivers, actually uninstalled AMD's AHCI disk driver, and replaced it with MSAHCI.SYS?
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Not that I know of. Unless AMD is just renaming the MS driver(they show up as AMD_SATA.sys in Device Manager). These AMD drivers are also 5-7% faster than MS's driver in random reads/writes(in my experience) so it has to be a different driver.
 
Z

zagood

Diamond Member
Mar 28, 2005
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What people normally see when they say their boot time increased with AHCI enabled is the drive detection time. On some gigabyte motherboards it can add 15 seconds or more from the time you hit the power button.
 
R

RhoXS

Senior member
Aug 14, 2010
207
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zagood said:
What people normally see when they say their boot time increased with AHCI enabled is the drive detection time. On some gigabyte motherboards it can add 15 seconds or more from the time you hit the power button.
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The time interval I measured started after the bios finished its boot and the instant "Starting Windows" appeared on the screen. I stopped the timing as soon as the rotating symbol goes away. At that point (also confirmed by the hard drive access light) it appears the Windows 7 start-up sequence is complete.

This interval is consistently just under 18 seconds when using an IDE interface. It is consistently almost 24 seconds with an AHCI interface.

Interestingly, and annoyingly, my Gigabyte GA-EP45-UD3P takes much longer to do its bios startup than Windows takes to get to a stable Desktop once it starts loading.
 
N

nusyo

Member
Feb 27, 2011
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RhoXS said:
Until a few days ago, I was using an IDE interfacing with my G2 SSD. The time from the instant "Starting Windows" (W7) appeared to a completed Desktop was consistently 17.8 seconds. Most applications started instantly. One application, Paperport, started with a couple second or so delay but even this was incredibly faster than the time it took with a HDD.

I happened to recently read some stuff extolling the virtues of AHCI, so I switched to AHCI a few days ago. Using the same starting and stopping points, the W7 start up time increased to almost 24 seconds. I was unable to notice any other change, good or bad, with respect to Apps starting and databases loading. Therefore, I reverted back to the seemingly faster IDE interface.

?
Click to expand...

Don't you have to do a fresh install when you switch from IDE to AHCI in bios? at least to take full advantage of SSD & AHCI

I believed I read this on OCZ forums a while back .... I could be wrong though
 
nvidiaintelftw

nvidiaintelftw

Senior member
Apr 4, 2011
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dorion said:
AHCI allows SSDs to use the Trim command. If the Trim command is used long term SSD performance degradation, due to internal fragmentation, is minimized.

Also NCQ is available to HHDs on AHCI allowing for some speed increases.

On the change in speed you should try the Intel AHCI drivers, I've heard they are loads better than the built-in W7 ones.
Click to expand...

http://downloadcenter.intel.com/Det...5&DwnldID=18063&keyword="AHCI+SATA+Driver"eng

Is this the driver you are talking about. i install it into my rig after my 470 comes back from RMA
 
Drsignguy

Drsignguy

Platinum Member
Mar 24, 2002
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nusyo said:
Don't you have to do a fresh install when you switch from IDE to AHCI in bios? at least to take full advantage of SSD & AHCI

I believed I read this on OCZ forums a while back .... I could be wrong though
Click to expand...

No, There is a Regedit tweek, then you reboot to bios and set it to AHCI.
 
E

Emulex

Diamond Member
Jan 28, 2001
9,759
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ncq is the mad gain. then again most scsi folks have had this tech for the last 20 years.
 
(sic)Klown12

(sic)Klown12

Senior member
Nov 27, 2010
572
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taltamir said:
NCQ massively increases performance on even light multi tasking. And with an SSD it is very important to getting good performance.
Click to expand...

I ran my old Torqx in IDE for a while and then switched to AHCI and I never noticed any significant gains. My multi-tasking consisted of encoding videos with Handbrake, running two virtual machines(Debian and OpenBSD), browsing the Internet, and some light gaming. Benchmarks like As-SSD, Crystal Disk Mark, and PC Mark Vantage did show some speed up, but only a few percent. This could be due to Indilinx chips not handling higher que-depths as well as newer SSD controllers so I'll have to do some testing with my Vertex 2.

Ps. Nice guide on AA.
 
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