Difference between IDE and SCSI ??

William Case billlinux at rogers.com
Tue Feb 5 16:47:06 UTC 2008

Hi all and thanks;

I find the answers and information you have given me very helpful, but
they don't quite get to the basis of the problem.  So let me try again.

On Sat, 2008-02-02 at 17:22 -0500, William Case wrote:
> 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 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; 

The schematics in the manual that came with my ASUS M2NPV-VM motherboard
show the Southbridge chip as nForce 430MCP.  I assume this has been
replaced by or contains a MCP51 IDE chip or configuration or something,
that is identified by my Hardware browser (hwbrowser).  I further assume
that the MCP51 is the controller for the SCSI bus.  However, if that is
true why is it called MCP51 IDE.

> while /sys/bus/scsi/devices/ lists my two drives as SCSI
> devices.  

When I look on the bottom of an old drive (from a 4-5 year old machine
-- not one of the Maxtors mentioned above, but a Maxtor nonetheless),
there are several chips.  One of those chips, I assume,  contains the
SCSI programm, protocol, commands, that interface with the SCSI bus or
SCSI bus controller. Or, is one of the chips hardwired to call on a
special driver for the harddisk?

> If I look in /dev/disk/by-id they are listed as
> "ata-Maxtor-5T040 ..." and "ata-Maxtor-6E040...".

To what does the ata in ata-Maxtor ... refer.  The hard disk chips or
the the MCP51.


My question is not about the history of the various chips etc., but is
about why do I get three different designations on my computer and how
do I disentangle the information being given me so that I know what is

I have googled to all the usual learning sites as well as the various
manufacturers and standards sites.

I have and I can look up the operation and function of the different
designations once untangled, but in all my reading descriptions seem
full of contradictions and open ended statements, each on its own making
sense, but completely confusing when I try to apply them to my own
existing machine.
Regards Bill

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