Nikos Chantziaras wrote:
On 01/22/2011 12:31 AM, Dale wrote:
Alan McKinnon wrote:
My notebook works like that too.
Hard disk works fine when everything is set to AHCI, but then the
system won't
boot from CD. So I enabled the IDE driver and the IDE driver for
CD-ROMs.
My take on this is that Dell had a vast stock of cheap-skate CD-ROM
hardware
and used them up. The engineering logic would have been "it doesn't
matter
that we use the slow interface for that device, it's still faster than
we can
get the data off the media."
And I thought there was something weird with me on this one. o_O I did
switch it back to AHCI after I got done booting the CD thingy. I really
can't tell any difference in speed between the two and neither could
hdparm -tT either.
hdparm measures raw throughput when reading continuously from one
position to another. AHCI improves performance when the disk needs to
read from several different places, which is the case in every day
use. It does this by providing a feature similar to what SCSI
provides: native command queuing (NCQ). You can read about what this
is and why we want it here:
http://en.wikipedia.org/wiki/Native_Command_Queuing
Other than copying a file and using time to measure how long it takes,
what is the best test of a hard drive's speed?
Also, does or can the kernel override the BIOS setting? I think it uses
AHCI no matter what is in the BIOS. It seems it would be at least some
difference in speed.
Nice link. The picture explained it best. I'm sort of simple. lol
Dale
:-) :-)
