ahci enabled, can I revert back


B

Bob H

I have recently enabled AHCI on my Win7 64 bit system which has 2 SATA
HD's and dual boots with WinXP 43 bit.
I haven't used WinXP for a while but that's not to say I won't.
From what I have read, whilst enabling AHCI for Win7, may well render
WinXP un bootable.
I don't have any problems with my Win7 system, but have found that there
doesn't seem to be any noticeable advantage of having AHCI turned on.
I use a driver update program which has backed up all my drivers prior
to installing updates earlier this week.
What I would like to know is can I restore the old drivers, then turn
off AHCI in the BIOS, so that WinXP will boot ok.

The reason I have posted on here is because I cannot find any relevant
information otherwise

Thanks
 
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P

Paul

Bob said:
I have recently enabled AHCI on my Win7 64 bit system which has 2 SATA
HD's and dual boots with WinXP 43 bit.
I haven't used WinXP for a while but that's not to say I won't.
From what I have read, whilst enabling AHCI for Win7, may well render
WinXP un bootable.
I don't have any problems with my Win7 system, but have found that there
doesn't seem to be any noticeable advantage of having AHCI turned on.
I use a driver update program which has backed up all my drivers prior
to installing updates earlier this week.
What I would like to know is can I restore the old drivers, then turn
off AHCI in the BIOS, so that WinXP will boot ok.

The reason I have posted on here is because I cannot find any relevant
information otherwise

Thanks
This isn't a solution. It is a reference, to describe how (some) drivers
work with Windows 7.

http://support.microsoft.com/kb/922976

The unused drivers are supposed to be disabled, and it has something to
do with reducing boot time.

Re-enabling a driver, would seem to make it a candidate at boot time. And
yet, I don't see a registry value defined in that article for a "vanilla IDE"
option for SATA. Maybe that means that built-in driver is always enabled
and available for discovery at boot ?

I would shutdown, go to the BIOS, flip the BIOS back to the non-AHCI/non-RAID
option for the disk controller, then attempt to boot Windows 7. If it works,
then chances are, the built-in AHCI driver would be disabled from then onward.

(It is the "vanilla" to AHCI case, that needs the registry tweak.)

If the test fails, you have the option of entering the BIOS and setting
it back to AHCI, so at least you can boot. And then seeing if there is any
more help here.

I don't think you'll get stuck. At most, you'll be entering the BIOS twice,
to see if it works, or doesn't work.

I think Microsoft at least owes us a state diagram, rather than us
having to figure this out, one test case at a time :-( I thought the purpose
of computers, was to make it easier to do something, not harder.
And surely, there must have been some other way to solve this problem.

And, as well, the logic of what is required, shouldn't vary from one brand
to another. The state diagram should not have different paths for
Intel chipsets, than for AMD chipsets. That would be lunacy, and show
a lack of proper architecting by the OS manufacturer.

Paul
 
B

Bob H

This isn't a solution. It is a reference, to describe how (some) drivers
work with Windows 7.

http://support.microsoft.com/kb/922976

The unused drivers are supposed to be disabled, and it has something to
do with reducing boot time.

Re-enabling a driver, would seem to make it a candidate at boot time. And
yet, I don't see a registry value defined in that article for a "vanilla
IDE"
option for SATA. Maybe that means that built-in driver is always enabled
and available for discovery at boot ?

I would shutdown, go to the BIOS, flip the BIOS back to the
non-AHCI/non-RAID
option for the disk controller, then attempt to boot Windows 7. If it
works,
then chances are, the built-in AHCI driver would be disabled from then
onward.

(It is the "vanilla" to AHCI case, that needs the registry tweak.)

If the test fails, you have the option of entering the BIOS and setting
it back to AHCI, so at least you can boot. And then seeing if there is any
more help here.

I don't think you'll get stuck. At most, you'll be entering the BIOS twice,
to see if it works, or doesn't work.

I think Microsoft at least owes us a state diagram, rather than us
having to figure this out, one test case at a time :-( I thought the
purpose
of computers, was to make it easier to do something, not harder.
And surely, there must have been some other way to solve this problem.

And, as well, the logic of what is required, shouldn't vary from one brand
to another. The state diagram should not have different paths for
Intel chipsets, than for AMD chipsets. That would be lunacy, and show
a lack of proper architecting by the OS manufacturer.

Paul
So in the link you gave me it tells you how to enable AHCI in windows by
means of changing values in the registry.
What I did was to change the values first, then rebooted into the BIOS
and changed the option there then booted back into win7

Now what I'd like to know is to do what you say, how should I proceed
regarding the said win7 registry values. I think I should change the
registry values first???

Thanks
 
P

Paul

Bob said:
So in the link you gave me it tells you how to enable AHCI in windows by
means of changing values in the registry.
What I did was to change the values first, then rebooted into the BIOS
and changed the option there then booted back into win7

Now what I'd like to know is to do what you say, how should I proceed
regarding the said win7 registry values. I think I should change the
registry values first???

Thanks
If there was a registry entry for "vanilla" interface mode, then I'd say
change it. If there isn't a registry entry, it implies the OS checks
each time, for that driver case. That's why I recommended just trying
the BIOS test first, to see if it would work, without doing something
to the registry. If it doesn't work, by just changing the BIOS
from AHCI --> vanilla, then you'd go back to "registry hunting".

Paul
 
B

Bob H

If there was a registry entry for "vanilla" interface mode, then I'd say
change it. If there isn't a registry entry, it implies the OS checks
each time, for that driver case. That's why I recommended just trying
the BIOS test first, to see if it would work, without doing something
to the registry. If it doesn't work, by just changing the BIOS
from AHCI --> vanilla, then you'd go back to "registry hunting".

Paul


Ok, I went into the BIOS and changed the setting back to IDE, rebooted
back into win7 ok, then changed the value in the registry, rebooted and
all seems ok again.

thanks
 
B

Bob H

There was no need to change from AHCI to IDE in order to install and run
XP. All you need do is to load the mobo AHCI drivers onto a floppy drive
and when you install XP hit F6 and install the AHCI drivers.
That way, you can run AHCI for 7 & XP.
Yes I know, but WinXP is already installed and I have read that if AHCI
is enabled in the BIOS and the boot into WinXP a BSOD occurs.
 
P

Paul

Bob said:
Yes I know, but WinXP is already installed and I have read that if AHCI
is enabled in the BIOS and the boot into WinXP a BSOD occurs.
There is a recipe for adding AHCI, that solves the "chicken versus egg"
problem with an Intel AHCI driver installation. This would be for adding
AHCI support to WinXP, after the fact. (I can't reach the site right now.)

http://forum.msi.com.tw/index.php?action=printpage;topic=106575.0

Normally, without that hack, being in IDE mode in WinXP, and installing
an AHCI driver for an Intel Southbridge, would result in failure to install.
And flipping the BIOS setting to AHCI, would cause a failure to boot.

But dumping a bunch of crap into the registry, following that recipe,
allows a person to hack it so it works.

And that hack, only handles a small fraction of all possible situations.

Paul
 
B

Bob H

There is a recipe for adding AHCI, that solves the "chicken versus egg"
problem with an Intel AHCI driver installation. This would be for adding
AHCI support to WinXP, after the fact. (I can't reach the site right now.)

http://forum.msi.com.tw/index.php?action=printpage;topic=106575.0

Normally, without that hack, being in IDE mode in WinXP, and installing
an AHCI driver for an Intel Southbridge, would result in failure to
install.
And flipping the BIOS setting to AHCI, would cause a failure to boot.

But dumping a bunch of crap into the registry, following that recipe,
allows a person to hack it so it works.

And that hack, only handles a small fraction of all possible situations.

Paul
There must be some part of the actual URL missing because the page does
/can't load.

Thanks anyway
 
B

Bob H

This link still works. The other link is a "printpage", while this is a
regular forum rendering.

http://forum-en.msi.com/index.php?PHPSESSID=4590f2c741082ef80b0bac3992b908d6&topic=106575.msg787092#msg787092


It's a good thing I kept a copy of the original, as a text file. It
had that link archived in it.

Paul
I've just had a read of the information there from the new link, and
although it is interesting reading, it is old, and some of it is not
relevant here.

Regarding the previous link, mmm, no it still won't load.

Thanks
 
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Y

Yousuf Khan

I have recently enabled AHCI on my Win7 64 bit system which has 2 SATA
HD's and dual boots with WinXP 43 bit.
I haven't used WinXP for a while but that's not to say I won't.
From what I have read, whilst enabling AHCI for Win7, may well render
WinXP un bootable.
I don't have any problems with my Win7 system, but have found that there
doesn't seem to be any noticeable advantage of having AHCI turned on.
I use a driver update program which has backed up all my drivers prior
to installing updates earlier this week.
What I would like to know is can I restore the old drivers, then turn
off AHCI in the BIOS, so that WinXP will boot ok.

The reason I have posted on here is because I cannot find any relevant
information otherwise

Thanks
Sorry, I saw this thread too late, it looks like there's already been a
lot of discussion on it. However, one thing I noticed is that once you
set the registry to enable AHCI in Win7, you don't need to change the
registry again to go back to using IDE drivers. Just leave the registry
as it is with AHCI and it'll know which are the proper drivers to choose.

The registry hack is to allow Windows to properly detect whether it's
running on IDE-compatibility or AHCI mode drivers. When Windows first
installs it locks it down to either AHCI or IDE depending on how you
first installed it, and prevents further boot-time detection (presumably
to speed up some kind of process). However, you can leave the registry
exactly as suggested for AHCI even while using IDE-compatibility mode.

Yousuf Khan
 
B

Bob H

Sorry, I saw this thread too late, it looks like there's already been a
lot of discussion on it. However, one thing I noticed is that once you
set the registry to enable AHCI in Win7, you don't need to change the
registry again to go back to using IDE drivers. Just leave the registry
as it is with AHCI and it'll know which are the proper drivers to choose.

The registry hack is to allow Windows to properly detect whether it's
running on IDE-compatibility or AHCI mode drivers. When Windows first
installs it locks it down to either AHCI or IDE depending on how you
first installed it, and prevents further boot-time detection (presumably
to speed up some kind of process). However, you can leave the registry
exactly as suggested for AHCI even while using IDE-compatibility mode.

Yousuf Khan

Thanks for the information Yousuf. A little late as you say but still
good to know.

If you read one of my latest post on this subject, this is what I posted:
'I tried to boot win7 64bit under AHCI mode again earlier but it
wouldn't for some reason.
I made the registry change again, then changed the setting in BIOS
from IDE to AHCI, rebooted and for some unkown reason win7 threw a
<wobbly and went into repair mode, but couldn't do the repair and said
there was no OS on the drive.
Anyway after a couple of reboots and booting normally I got back into
windows again, thankfully.
I have no ideas as to what may have happened to cause the said
situation, but I think I will leave well alone for the time being.'
Then I posted this:
When Win7 threw the wobbly, as I said it went into repair mode and I let
it do its thing. Then it took a few reboots and repairs to enable normal
booting.

I have just checked the registry entry which I changed previously from 0
to 3, and it is or has changed back to 0 again, so maybe the repair mode
did that. I honestly don't know how or what happened only what has
happened.


So you have now clarified the above situation , in that I should not
have made any further changes to the registry setting.
Now the registry setting is at 0 for AHCI mode should I wish to change
back to that in the BIOS.

Thanks
 
Y

Yousuf Khan

Then I posted this:
When Win7 threw the wobbly, as I said it went into repair mode and I let
it do its thing. Then it took a few reboots and repairs to enable normal
booting.

I have just checked the registry entry which I changed previously from 0
to 3, and it is or has changed back to 0 again, so maybe the repair mode
did that. I honestly don't know how or what happened only what has
happened.


So you have now clarified the above situation , in that I should not
have made any further changes to the registry setting.
Now the registry setting is at 0 for AHCI mode should I wish to change
back to that in the BIOS.

Thanks
Yeah, a repair is kinda like a minor reinstallation of Windows. Just
like when you install Windows for the first time, the install disk
determines whether you are running on IDE or AHCI drives, and it locks
the registry setting down based on it.

Yousuf Khan
 
B

Bob H

Yeah, a repair is kinda like a minor reinstallation of Windows. Just
like when you install Windows for the first time, the install disk
determines whether you are running on IDE or AHCI drives, and it locks
the registry setting down based on it.

Yousuf Khan
I downloaded and installed HDTune and then did some tests with it on my
sata drive.

On the Samsung HD5021J HD with IDE selected in the BIOS
For Read
Max - 63.9mb/s
Min - 113.9 mb/s
Average - 94.9 mb/s
Access Time - 12.5 ms
Burst rate - 191.8

With AHCI mode selected
Max - 113.9 mb/2
Min - 3.7 mb/s
Average - 91.9 mb/s
Access Time - 12.5 ms
Burst Rate - 196.6 mb/s

Also with AHCI enabled boot up time was 16seconds longer than with IDE mode.

So from these results I will continue to use IDE mode, unless someone
recommends different.
 
E

Ed Cryer

I downloaded and installed HDTune and then did some tests with it on my
sata drive.

On the Samsung HD5021J HD with IDE selected in the BIOS
For Read
Max - 63.9mb/s
Min - 113.9 mb/s
Average - 94.9 mb/s
Access Time - 12.5 ms
Burst rate - 191.8

With AHCI mode selected
Max - 113.9 mb/2
Min - 3.7 mb/s
Average - 91.9 mb/s
Access Time - 12.5 ms
Burst Rate - 196.6 mb/s

Also with AHCI enabled boot up time was 16seconds longer than with IDE
mode.

So from these results I will continue to use IDE mode, unless someone
recommends different.
Can you safely swap back and forth with just a change to the BIOS entry?

Ed
 
E

Ed Cryer

I downloaded and installed HDTune and then did some tests with it on my
sata drive.

On the Samsung HD5021J HD with IDE selected in the BIOS
For Read
Max - 63.9mb/s
Min - 113.9 mb/s
Average - 94.9 mb/s
Access Time - 12.5 ms
Burst rate - 191.8

With AHCI mode selected
Max - 113.9 mb/2
Min - 3.7 mb/s
Average - 91.9 mb/s
Access Time - 12.5 ms
Burst Rate - 196.6 mb/s

Also with AHCI enabled boot up time was 16seconds longer than with IDE
mode.

So from these results I will continue to use IDE mode, unless someone
recommends different.
I've done tests on my two HDs. One is internal SATA, 640GB; the other
USB 1TB.
BIOS setting AHCI.


HD Tune Pro: WDC WD6400AAKS-22A7B Benchmark

Test capacity: full

Read transfer rate
Transfer Rate Minimum : 59.2 MB/s
Transfer Rate Maximum : 116.3 MB/s
Transfer Rate Average : 95.6 MB/s
Access Time : 12.3 ms
Burst Rate : 141.9 MB/s
CPU Usage : 11.3%


HD Tune Pro: Iomega External HD Benchmark

Test capacity: full

Read transfer rate
Transfer Rate Minimum : 29.0 MB/s
Transfer Rate Maximum : 31.9 MB/s
Transfer Rate Average : 29.4 MB/s
Access Time : 17.0 ms
Burst Rate : 29.4 MB/s
CPU Usage : 16.7%

The access graphs were very interesting for comparison.
The internal drive had a drop line access time from 0GB to 640GB.
The USB external one was a horizontal line from 0 to 1,000GB.

Ed
 
B

Bob H

Can you safely swap back and forth with just a change to the BIOS entry?

Ed
Yes I have done just that without any problems, as the registry has not
been changed.
 
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C

Char Jackson

I've done tests on my two HDs. One is internal SATA, 640GB; the other
USB 1TB.
BIOS setting AHCI.


HD Tune Pro: WDC WD6400AAKS-22A7B Benchmark

Test capacity: full

Read transfer rate
Transfer Rate Minimum : 59.2 MB/s
Transfer Rate Maximum : 116.3 MB/s
Transfer Rate Average : 95.6 MB/s
Access Time : 12.3 ms
Burst Rate : 141.9 MB/s
CPU Usage : 11.3%


HD Tune Pro: Iomega External HD Benchmark

Test capacity: full

Read transfer rate
Transfer Rate Minimum : 29.0 MB/s
Transfer Rate Maximum : 31.9 MB/s
Transfer Rate Average : 29.4 MB/s
Access Time : 17.0 ms
Burst Rate : 29.4 MB/s
CPU Usage : 16.7%

The access graphs were very interesting for comparison.
The internal drive had a drop line access time from 0GB to 640GB.
The USB external one was a horizontal line from 0 to 1,000GB.

Ed
For the external drive, it looks like you're testing the throughput of
your USB bus.
 

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