Difference between IDE and SCSI ??

William Case billlinux at rogers.com
Sat Feb 2 22:22:31 UTC 2008

Thanks Les;

On Sat, 2008-02-02 at 11:57 -0800, Les wrote:
> On Sat, 2008-02-02 at 13:39 -0500, William Case wrote:
> > Hi;
> > 
> > Can someone briefly explain to me the difference between an IDE (ATA)
> > and a SCSI device.  After having done due diligence with google searches
> > etc., I am still in a quandary. Nothing I read seems to be consistent.
> > Every time I think I have it figured out, I read a reference that calls
> > for or lists IDE devices that I think should be a SCSI reference and
> > vice versa.  Even going to the various standards sites doesn't clarify
> > it for me.  In fact it makes it more confusing.

I have used the pcguide and the pcworld site.  Along with Wikipedia, I
always go there first.  The summary of those sites seems to be the

IDE ==> SCSI ==> (P)ATA.  That is simple and fairly easy to follow.  The
advancements from one to the next at first seem obvious.  So let me put
the question in another way.

I have two Maxtor 40 Gb drives and AMD 64 X2 CPU on an ASUS M2NPV-VM
motherboard.  I am using F8 as my operating system.

How come? :
My Hardware browser, under 'IDE Controllers' lists, nVidia Corporation
MCP51 IDE; while /sys/bus/scsi/devices/ lists my two drives as SCSI
devices.  If I look in /dev/disk/by-id they are listed as
"ata-Maxtor-5T040 ..." and "ata-Maxtor-6E040...".

I also have seen them or similar drives referred to as any of IDE,
(P)ATA or SCSI. I have also seen the terms used apparently
interchangeably over the last 2 or 3 years.  I would have to go search
to quote exactly where, but I do remember the use of these terms.

I am not confusing them with SATA drives which are something else again.
If they are all one and the same, I will henceforth just mentally
substitute the word PATA for any of the other two designations.  But I
have a sneaking suspicion they are not exactly the same and should not
be used interchangeably on a modern system as they appear they sometimes

My original question was not to have someone else do my investigation
for me, but to either give me reassurance that all three, IDE, PATA and
SCSI are exactly the same thing and can be used interchangeably on a
current system, or to point out where I have missed the difference and
when I should use one term over the other.

Regards Bill

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