Difference between IDE and SCSI ??

William Case billlinux at rogers.com
Tue Feb 5 18:54:25 UTC 2008

Hi Les and thanks;

Your yes and no type answers helps a lot.

On Tue, 2008-02-05 at 11:07 -0600, Les Mikesell wrote:
> William Case wrote:
> > 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.
> If you want the really easy version, count the pins in the cable.  If 
> you have a wide 40-pin connector, possibly with an 80-wire cable, you 
> have Parallel ATE (also known as IDE).  Scsi would have 50 or 68 pins on 
> a connector or 80 on hot-swap SCA connectors that include power.
According to my manual I have an IDE connector (40-1 pin PRI_IDE; 40-1
pin SEC_IDE).

> >> 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.
> The disk size is another hint. Scsi drives would be 36 Gb, IDE's 40.
> >> How come? :
> > 
> >> My Hardware browser, under 'IDE Controllers' lists, nVidia Corporation
> >> MCP51 IDE; 
> That is your controller.
> >> 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?
> The current kernel calls everything scsi.  It isn't.


> >> 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.
> The interface type.

I guess.  Still trying to figure out the interface type exactly.
> > 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
> > what?
> You have two hardware designations because you have a controller and 
> disks.  The third is a lie.
So then my disks are SCSI (or something else) and my controller is IDE

> > 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.
> So far you have not described any actual scsi hardware.

Does your comment mean that there appears to be no truly scsi hardware,
or, does it mean I have failed to find and send to the mailing list some
vital piece of information that I should have sent.  If it is the
second, tell me what I should be looking for and where to find it,
please ?

Regards Bill

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