OT: What advantage does AHCI have over IDE ?

[Andrew]

Symptoms:

Clock losing time. So time for new CR2035 (6 years old).

Deliberated over a hot swap, but decided a quick swap was easier, however it still lost something because Win7/32 flashed up a message about AHCI and didn't give me enough time to read it and I must have pressed Yes to AHCI.

PC would not boot or respond to CTRL-ALT-DEL so power off and on and got into the bios where I noticed that no disks were recognised.

managed to get back to IDE and eventually it reverted from hissy-fit to normal mode.

Single HD is a Western Digital SATA a couple of years old added some time after upgrading to Win7.

What does AHCI do that IDE mode doesn't ?. I don't need hot-swap so unless there is a speed advantage, what's the point ?.

[Caecilius]

AIUI: AHCI is SATA, whereas IDE is emulated ATA.

So AHCI will give you command queuing and all those nice things that come with SATA; whereas IDE will emulate a dumb (by modern standards) ATA disk.

Mainly performance improvements I would suspect, especially with muliple processes accessing the disk where command queing can help. There may also be some size limits with IDE.

[The Natural Philosopher]

Caecilius gave you the advantages, and I am surprised that a machine that new would use IDE mode.

Could be simply that win 7 is crap and wont boopt from anything eklse or it MAY be that the disk would like to be AHCI BUT yoiu need to dsisable secure boot or something to use that gfetaure. I.e. you may still not have it right

Oh. win 7 is crap, but can be marginally de-crapped.

Looks about ten times worse than installing a custom wifi driver in linux...

[John Rumm]

Performance advantages mainly.

Win 7 supports AHCI out of the box, but it will only install the drivers for it if AHCI is active when you install it. If you install in IDE mode you will have to do some poking about the get the drivers loaded so that windows will play nice with that disk again after changing to AHCI mode.

[Brian Gaff]

I'm a bit concerned that just swapping out a battery can jumble up the bios settings. Most allow several minutes to change it over, more than enough time for me a blind bloke with fingers too big to do the deed.

If some are just losing it, then I'll steer clear of those makers! Non volatile storage is hardly a new concept either so really it does seem odd that this part is affected by a battery in the first place. Brian

[Steve Walker]

I presume that it is a legacy thing. A battery backed real-time clock is required and these chips usually have a small amount of battery backed CMOS ram built-in. It simply saves having another chip on the board.

SteveW