What's the difference Using AHCI Mode and Disable Mode?

[zhimama]

I've been using kalyway10.5.2 DVD for several weeks. Until now, it rus pretty.

 

But, just knew that ( Haven't tried others ) Kalyway10.5.2 CAN run without setting BIOS to AHCI Mode.

 

(I didn't know this when i was installing it, so i did set to AHCI mode for the whole system installation.)

 

And now, i turn the AHCI mode to Disable Mode. And Leopard 10.5.2 still works fine.

 

So,

 

1) what is the difference between using AHCI AND Disable it? Is it impact the speed of leopard ?

 

2) For another HDs, which i installed Winxp pro 64bit, because i had been told that x86 should run on AHCI mode, when i was installing winxp , i had to install it as DHCI mode, in order to switch between mac x86 and winxp from the BIOS setting.

If my current leopard is no longer needed running on AHCI mode , i think that i can install winxp as a normal mode.

So, Does AHCI mode affect the speed of win xp ? quicker than normal mode? or ...

 

Any idea ?

[Superhai]

AHCI is faster. How much depends on your hd. But if you're not running any intensive programs you would hardly notice the difference.

[zhimama]

AHCI is faster. How much depends on your hd. But if you're not running any intensive programs you would hardly notice the difference.

 

Yes, i did feel the speed of difference. Especially, under the winxp pro, when i was using MAYA.

that is why i put the question above.

 

But, anyway, thanks for ur reply.And also i've got answers from somewhere. And someone said that 8% speed up can be improved on ACHI mode, also as u mentioned if people do not run some heavy applications ,they won't feel the difference.

[LioNEXT]

Yes, i did feel the speed of difference. Especially, under the winxp pro, when i was using MAYA.

that is why i put the question above.

 

But, anyway, thanks for ur reply.And also i've got answers from somewhere. And someone said that 8% speed up can be improved on ACHI mode, also as u mentioned if people do not run some heavy applications ,they won't feel the difference.

 

I am not so sure what difference one could get. I have tested extensively with Xbench's disk test for both AHCI and non-AHCI mode to figure out any difference at all and no difference was there. Another factor, in AHCI mode, todays disk can run native command queuing, which unless you are running servers, does not help at all and rather slows the speed down (google about this). So in my feeling any benefit you get from AHCI gets wiped out by NCQ (which again is good for server environments and not typical desktops). Please illuminate me what applications explicitly benefits from this mode and I will test them out to satisfy my curiosity. Thanks.

[Superhai]

While it is true that NCQ could slow down in a single sequential read because of the protocol overhead, that was a problem barely noticable on the first NCQ disks and more an urban myth that one should avoid it. TCQ which the Raptor disks uses is more advanced and its protocol had much heavier overhead and so was the disk that gave fuel to this myth.

 

The benefits of NCQ is in a virtual memory and multitask OS, or as mentioned if you use it on a server. And most importantly a big benefit is lower disk wear as the heads dont need to move so much as without NCQ. Also if your disk is heavy fragmented NCQ helps.

 

Newer disks have larger caches so NCQ is more efficient.

 

NCQ works by reading a certain amount of commands, reorganizing where they take place on the hd and then issue them. Here is also the overhead when the read and reorganizing takes place, but as your CPU or hd controller queue manager is much faster than your disk anyway, you would need heavy sustained sequential read or write to notice the overhead.

[LioNEXT]

While it is true that NCQ could slow down in a single sequential read because of the protocol overhead, that was a problem barely noticable on the first NCQ disks and more an urban myth that one should avoid it. TCQ which the Raptor disks uses is more advanced and its protocol had much heavier overhead and so was the disk that gave fuel to this myth.

 

The benefits of NCQ is in a virtual memory and multitask OS, or as mentioned if you use it on a server. And most importantly a big benefit is lower disk wear as the heads dont need to move so much as without NCQ. Also if your disk is heavy fragmented NCQ helps.

 

Newer disks have larger caches so NCQ is more efficient.

 

NCQ works by reading a certain amount of commands, reorganizing where they take place on the hd and then issue them. Here is also the overhead when the read and reorganizing takes place, but as your CPU or hd controller queue manager is much faster than your disk anyway, you would need heavy sustained sequential read or write to notice the overhead.

 

 

Superhai,

 

 

Thanks for the explanation. That makes some sense. So what exactly is AHCI? I dont know much about it. And given the pros and cons of using AHCI with NCQ enabled; (I have not so far come across how to disable NCQ in AHCI mode in OS X), are there any applications that can take real advantage for this. General OS doesn't seem to benefit, if at all. I am going to buy the new VelociRaptors. Is TCQ that big of a problem on the recent raptors?

 

Finally, what have you modified your IOUSBFamily for? And what is Logging AppleSMBIOS.kext and TurnLidOn (possibly laptop)?

[volte]

In my experience, AHCI adds about 10-20 seconds onto my boot time. I hate it. Gotta sit there and watch it try to twist itself all up into just one more layer of translation, I can't help but think this is partly the cause for my horrible xbench HDD score dragging my otherwise 285+ score down to sub 200. Unacceptable, definitely notice it too day to day, launching apps etc, reading files off the HD. My computer should be snappy, I've got pretty beefy stats otherwise.

 

When I try to disable AHCI via BIOS, it boots up much quicker, but once I get to the grey apple loading screen, a few seconds later I'll receive a pixelated "NOT" symbol (think, no smoking symbol without the cigarette).

 

I've got the GA-EP45C-DS3R, is there anyway to patch my system kexts to get it to run without AHCI enabled?

 

Much appreciated,

 

volte

[davidcmc]

In my experience, AHCI adds about 10-20 seconds onto my boot time. I hate it. Gotta sit there and watch it try to twist itself all up into just one more layer of translation, I can't help but think this is partly the cause for my horrible xbench HDD score dragging my otherwise 285+ score down to sub 200. Unacceptable, definitely notice it too day to day, launching apps etc, reading files off the HD. My computer should be snappy, I've got pretty beefy stats otherwise.

 

When I try to disable AHCI via BIOS, it boots up much quicker, but once I get to the grey apple loading screen, a few seconds later I'll receive a pixelated "NOT" symbol (think, no smoking symbol without the cigarette).

 

I've got the GA-EP45C-DS3R, is there anyway to patch my system kexts to get it to run without AHCI enabled?

 

Much appreciated,

 

volte

 

I have the same question...

My mobo is a GA-EP43-DS3L and I don't like AHCI mode as it increases the boot time.

I'm currently using Windows Vista with SATA in IDE mode.