[Leaplist] CentOS question ....

["pberry2" at cfl.rr.com]

Fred Moore wrote:
> On Friday 19 January 2007 09:16, Steve Litt wrote:
>   
>> On Friday 19 January 2007 00:14, Damien McKenna wrote:
>>     
>>> On Jan 19, 2007, at 12:14 AM, David Simmons wrote:
>>>       
>>>> It's weird that your optical drives doesn't show up in
>>>> dmesg....maybe double
>>>> check connections....replace IDE cables....re-quadruple check the
>>>> jumpers
>>>>         
>>> Almost every time I've heard of a problem with a newly installed HD
>>> or optical drive not working it has been because of the cable and/or
>>> jumpers set incorrectly.  Remember, if you have to drives on a cable
>>> the drive at the end of the cable should be jumperred for Master
>>> while the one in the middle should be Slave (I don't do the cable-
>>> select thing myself).  Also, it is best to do one drive per cable,
>>> but still remember that it must be jumperred correctly or it probably
>>> still won't work.
>>>       
>> I've never heard that. Is that for IDE drives? What would happen if the
>> master were the middle and the slave were the end?
>>     
>
> depends on the system.. sometimes its ok.. many times its not.. 
> sometimes your bios saves you...  sometimes not..  more than likely not.. 
>
> think 
> controller (channel), next drive (slave), next drive (master)  no more cable 
>
> then they by default get assigned during boot time.. (unless bios screws with 
> you).. 
>
> 1st IDE controller  
> 	channel A, slave   (hda)   (first cable 1st drive)
> 		partition 1   (hda1)
> 		Partition 2   (hda2)
> 		....
> 	channel A,master (hdb)  (first cable 2nd drive)
> 		partition 1   (hdb1)
> 		Partition 2   (hdb2)
> 		....
> 	channel B, slave, (hdc)   (second cable 1st drive)
> 		partition 1   (hdc1)
> 		Partition 2   (hdc2)
> 		....
> 	channel B, master (hdd) (second cable 2nd drive)
> 		partition 1   (hdd1)
> 		Partition 2   (hdd2)
> 		....
> 2nd IDE controller
> 		....
>
> if you use cable select (CS) on your drives this is the order they will be 
> assigned..  But like others have said.. I always jumper my drives, don't 
> really know why.. guess just an old habit.. getting too old to change.. 
>
> and for performance you don't want slower things like cdroms on the same 
> channel with your disk drives..   the channel always runs at the speed of the 
> lowest device.. 
>
> Steve I seem to remember we fixed one of your not booting mobo's by setting 
> this correctly..  or perhaps I remember wrong.. . its been years.. many holes 
> have developed in the gray matter.. Fred
>
>
>
>
>
>
>
>
>   
>> SteveT
>>
>>
>> Steve Litt
>> Author: Universal Troubleshooting Process books and courseware
>> http://www.troubleshooters.com/
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>>     
>
>   
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>   
Many times, in repair of PCs, I have had to move the jumpers from CS to 
MS/SL.

Here is  what I think is a possible "why".  the BIOS on the mainboard 
selects the drives from the pool of "Cable Select" jumpered devices, 
based on either a wire that is not terminated on the IDE cable, (there 
is often a punced out wire in the cable) or, a presumption involving the 
MBR on one drive, not on the second drive(?). 

What I do know, is that at many installfests and for many customers who 
brought computers to me, the problems in booting are solved when I put 
the correct order to the drive cables and jumper for Master and Slave.

My personal choice is to only run a single drive on each IDE channel, 
due to the flaws in the IDE standard, and to run the DVD/CDroms there, 
on IDE 1 and 2, and a ATA controller card or a SCSI card, as required, 
for the hard drive devices.  

As soon as the OS assumes control from the BIOS, we would have errors 
when the IDE cable devices are set for Cable Select.