I just installed an internal 10k scsi drive in less than 10 minutes.
You dont need a dual channel card an atto ul4s will work. http://www.attotech.com/ultra4s.html
You need to use these, and not the ul3s for g5 compatibility.
I'll do a document with pictures by the end of today showing what to do.
I have to leave it on all day to check heat....and its still winter....
but atlas IV 10k drives are not so hot - but a little more noisy than raptors.
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to install this i used an internal round scsi cable i bought directly from adaptecs online store.
You can see this in the picture.
If you install this cleanly and tie up cables correctly, this is by far the best solution.
Airflow is maintained everywhere.
Im taking power from a splitter with the dvd drive.