Setting AHCI / IDE to IDE mode, limits xfer speeds to 150MB/sec?

[VirtualLarry]

Is this true, that you get a max of SATA 1 (150MB/sec) in Win7 if you set your mobo to IDE mode?

Because that seems to be what I observed with a friend's computer lately.

 

[Cerb]

Maybe? I've only ever needed that with HDDs that couldn't even do 100MBps. Since that setting is to handle legacy devices and OSes, it wouldn't be surprising, but I'm not sure that it's necessarily the case, either.

 

[VirtualLarry]

The rig is a 780G mobo, with an Athlon II X4 3.0Ghz. Drives include a new 500GB WD Caviar Black (which I am told is AF), and a 30GB OCZ Agility SSD as the OS / boot drive.

Running HDtune, I get a virtually straight line for the WD Black at 130MB/sec, and the same with the SSD, except pinned to 150MB/sec. I know for a fact that that SSD model is capable of 180MB/sec or more, so it's clear that there is some sort of interface limitation going on.

 

[Cerb]

That's awfully new hardware to be running IDE mode...

 

[VirtualLarry]

It used to be in a dual-boot, with XP on another mechanical (SATA) HDD.

 

[Engineer]

SATA I has a max speed of 1.5Gb(its)/sec...so 150MB(ytes)/sec would probably be pretty close to the MAX limit anyway whether it be IDE or AHCI.

 

[VirtualLarry]

But why would a SATA 2 SSD, and a SATA 6G HDD, be running at SATA 1 speeds, on a SATA 2 mobo?

 

[Elixer]

Because 'IDE mode' limits it to the max that mode can handle ?

Moral of the story is, don't use IDE mode if you want full SATA 2 speeds.

 

[Engineer]

But why would a SATA 2 SSD, and a SATA 6G HDD, be running at SATA 1 speeds, on a SATA 2 mobo?

Oh sorry, I misread your first statement as the device or motherboard was limited to SATA I because that's what it was designed to do. Didn't realize that they were SATA II or III devices.

 

[BFG10K]

Is this true, that you get a max of SATA 1 (150MB/sec) in Win7 if you set your mobo to IDE mode?

Absolutely not. Here's my old Intel 320 SSD running under IDE mode on said OS: