[rescue] u2 drive trays

Frank Van Damme frank.vandamme at student.kuleuven.ac.be
Mon Aug 18 17:20:43 CDT 2003

On Monday 18 August 2003 23:10, Jonathan C. Patschke wrote:
> Yes.  ATA does NOT negotiate well when you have more than one device on
> the chain.  This is completely separate from the issue of negotiating
> the entire bus down to the lowest present spec.  ATA has a design flaw
> that causes 30%-60% of the effective throughput to be eaten up with
> chatter/busywaiting when there are multiple periphreals present.  There
> are benchmarks out there on the web, but I'm too lazy (read as: busy)[0]
> to look them up right now.

This one is really, really hard to weed out. While the ide protocol obviously
sucks, the bus does not "negotiate till the lowest spec". An udma33 and an
udma133 disk will each operate at their own speed. They will fight for
bandwidth however. Also, these speeds don't get used automatically, you have
to set the right settings (with eg hdparl on linux).

Frank Van Damme    http://www.openstandaarden.be
~~~~~~~~~~~~~~~    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"Je pense, donc je suis breveti."

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