So, just what good is AHCI?

[Painman]

TBH, I thought my system performance was worse when I did my last install of Vista with this mode enabled in BIOS. I don't run RAID, and I don't have any e-SATA devices, but hey, things can change.

First difference I noticed was a loss of desktop snappiness, esp. in Explorer. In AHCI mode, there seems to be a bit of lag in opening Explorer windows and loading up icons/thumbnails for my files. Actually, a lot of lag loading up those icons/thumbnails.

Running HDTune reveals that Burst Mode performance ranges from somewhat to much worse:

ST3500320AS: 93.7 MB/S AHCI, 146.5 MB/S IDE :Q

ST3500630AS: 125.1 MB/S AHCI, 140.9 MB/S IDE

ST31000333AS: 140.4 MB/S AHCI, 157.8 MB/S IDE

CPU usage in AHCI mode was a little better across the board, but CPU usage in IDE mode never exceeded 3.7%. Other performance benchmarks were essentially identical. I couldn't generate any synthetic write speed benchies (I'm too cheap).

The ST31000333AS drive is new (Seagate firmware FUD = good deals on HDDs for me). I started copying the contents of ST3500630AS to it, but aborted the process after 15 minutes or so after noting an xfer speed that barely exceeded 25 MB/Sec on the copy operation. This was a 200 GB copy, with file sizes ranging from a handful of bytes to DVD sized ISOs and everything in between. Restarting the operation in IDE mode netted a write speed pretty much twice that fast.

Did I configure something incorrectly? Is this yet another case of Newer != Better for folks who run simple configurations?

 

[BlueAcolyte]

It's really just for server drives. Disable it.

 

[Modelworks]

These are the features of AHCI, some are also supported in SATA. If you got it enabled just leave it alone, not going to hurt anything and may help with random writes.

? Support for 32 ports
? 64-bit addressing
? Elimination of Master / Slave Handling
? Large LBA support
? Hot Plug
? Power Management
? HW Assisted Native Command Queuing
? Staggered Spin-up
? Cold device presence detect
? Serial ATA superset registers
? Activity LED generation
? Port Multiplier

 

[Painman]

I think something might have gone wonky with my disk I/O subsystem. I just reinstalled Vista (not due to this issue, this reinstall was planned) with ACHI still enabled in BIOS -- nothing strange going on now that I can see. I'm re-doing that 200 GB copy to another drive as a test, and throughput looks good, general behavior feels snappy.

 

[taltamir]

run a multi tasking test...

Torrents, rar extractions, etc...

In some of those that I have seen, going from about 100MB/s the speed fell to SINGLE DIGITS without AHCI, but only fell to 50-70MB/s with it on.

also, it highly depends on the drive implementation. AHCI ALLOWS the drive to perform NCQ... but some drives have horrible implementation...
For example, a motherboards "raid5" capability should not be used to judge RAID5 as a whole, since it is a shittly implemented "checkbox feature". Many drives have such poor implementation of NCQ

 

[taltamir]

FUD = fear uncertainty and doubt.
There is no doubt or uncertainty that their firmware was broken. and the fear in the term is not the justified fears of someone who doesn't want to lose his data...

an example of FUD is the IBM salesmen saying "nobody got fired for buying an IBM" to an IT, or saying "yes but will an AMD cpu be able to run your programs that were designed for an intel CPU"

 

[rarebear]

I can run several DVD/CD based Boot Programs with it on VS Boot Apps Not Seeing My HDD to do a Image Restore (Acronis True Image) plus many other boot disk utilities not running in plain Sata mode.......