Re: Daisychaining 5.25 " Drives

[Don Bruder <dakidd@sonic.net>]

In article <UIidnZ0empu7CpjYnZ2dnUVZ_q2dnZ2d@comcast.com>,
 "Bill Garber" <willy46pa@comcast.net> wrote:

> "Mark Percival" <mark@syndicomm.com> wrote in message
> 1157993693.674164.148300@e3g2000cwe.googlegroups.com">news:1157993693.674164.148300@e3g2000cwe.googlegroups.com...
> :
> : Robert O Greenawalt wrote:
> : > Who knows the limit of daisychaining such drives with one controller
> card?
> :
> : Two drives per card.  I'm not sure which 3rd party controller card Bill
> : is refering to.
> :
> : Mark
> :
> : http://www.syndicomm.com/~mark/DM8/
> 
> 
> The Rana drive controller was one that I know of,
> but, that may have required Rana drives as well,
> I am not sure exactly. I'd have to research that.

No research needed - Even with the Rana controller, a standard 
Apple-issue drive can't "pass along" to anything beyond drive 2 due to 
the wiring of the connectors/logic on the drive boards (not the 
controller card, but the drive boards)

The second connector on the second drive is effectively a "dead end", 
because the drive-select signal to turn on the second drive is "faked 
up" in logic by the board of the first drive prior to the signals being 
passed to the second connnector. Thus the second drive in the chain 
always sees either "nothing at all" or "They're talking to me". The 
first drive sees "They're talking to me", and the "faking up" process 
puts a "nothing at all" signal on the second connector. If the first 
drive sees a "We're NOT talking to you" signal, it fakes up the "We're 
talking to you" signal and puts it on the second connector, and the rest 
of the signals get routed to the second connector for drive 2 to play 
with.

So the drives are the critical concept with the Rana controllers - 
Without "non standard" drives that can pass along a two (or more) bit 
drive-select signal to the "next drive" connector, it can, like the 
Apple-issue cards, only talk to two drives max.

-- 
Don Bruder - dakidd@sonic.net - If your "From:" address isn't on my whitelist,
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