[G4] Did I miss my bus?

[jeff small]

To clarify,  here is the question (phrased much more clearly) and the 
answer from Apple tech forums:

http://discussions.info.apple.com/WebX?12@23.uJ84a1w3ehL.4@.3bbd3c47/1

  Very educational (for me anyway):

I'm adding a WD SE 120 to my machine. I'm putting the original IBM 80 
on the ATA 66 bus, and the new drive on the ATA 100. My understanding 
up to this point has been that *all* drives should be set to cable 
select.

I just read a comment by Damien in another article stating that each 
drive should be set to master for optimum performance. Is this an 
official Apple recommendation? Is there one?

If I set both drives to master, should they be "master only" and then 
"master + slave" if I add additional drives to their respective 
busses later?

Thanks ahead of time
jeff in seattle

Answered:

Hey Jeff,

  IDE only access' a single drive per channel at a time. Damien's 
point is that when you add a second drive it is best for performance 
to add that drive to the second channel as that channel's Master 
drive so that both drives on the computer can access concurrently. If 
both drives are installed as Master/Slave or Cable Select on the same 
channel/cable then they would alternate access and be half as fast 
when both are active.

  I personally prefer to set my drives with Master/Slave jumpers 
instead of leaving that to cable select. Cable Select is a method 
where the bus automatically sets Master/Slave. The end result is the 
same if everything is working but I feel comfortable setting them 
manually during the install.

  The two musts are that you choose which way you are going to go and 
stick with that not mixing the drives with one set Cable Select and 
the other set with a jumper to Master or Slave. And the end connector 
is always used for the Master Drive.

  The setup you are planning sounds exactly appropriate for best 
performance. Take your pick on whether to set your drives both as 
Master or as Cable Select and you'll most likely get the same result. 
(Damien was referring to the fact that a drive is still the Master 
drive if it is installed physically in the Master position on a cable 
no matter if the jumpers are set Cable Select)

  And yes, Apple did say that setting Master/Slave instead of Cable 
Select is an approved method. I choose to manually set it that way 
out of surety that it will work the way I want it to work.

Rick
MacGurus.com





At 9:22 AM -0800 12/24/02, jeff small wrote:
>Thanks for the reply.  The dual has *two* ATA busses, one ATA 100 
>and one ATA 66.
>My new drive is a WD SE 120, btw.
>
>Thanks
>jeff
>
>At 8:51 AM -0800 12/24/02, T. Brown / groucho wrote:
>>On Tuesday, December 24, 2002, at 08:38  AM, jeff small wrote:
>>
>>>I'm installing an additional IDE drive in my dual 1ghz.  Does it 
>>>matter which bus it's installed on?  I thought I had read 
>>>somewhere that there was a protocol for adding drives; I can't 
>>>find any reference now.
>>>
>>
>>It would be best to put it on the same buss as the original drive. 
>>There is a slight speed hit if you put it on the CD/DVD drive buss. 
>>I do have a drive in the atapi chain, but it is for MP3 / iTunes 
>>storage. The drive is a WD 80 gig special edition
>>with an 8 meg cache. I notice no speed hit with it for that 
>>purpose. With other drives though, there was a noticeable 
>>difference.
>>
>>
>>HTH,
>>groucho
>>