I just installed a SAMSUNG HD753LJ 750Gb drive (32Mb cache - the F1 Spinpoint) in my 2008 24" iMac... but was surprised by these results. The drive *seems* faster with acoustic management set to QUIET, looking at the scores below (XBench), BUT it boots slower than when the AAM is set to PERFORMANCE... but when it's set to PERFORMANCE, the score drops BUT the boot time is SIGNIFICANTLY reduced... 
I use an Ubuntu CD to set AAM to level '128' (quietest)
I use an Ubuntu CD to set AAM to level '254' (loudest - "performance")
How so??
I use an Ubuntu CD to set AAM to level '128' (quietest)
Code:
Disk Test 77.53
Sequential 113.01
Uncached Write 194.19 119.23 MB/sec [4K blocks]
Uncached Write 184.82 104.57 MB/sec [256K blocks]
Uncached Read 52.01 15.22 MB/sec [4K blocks]
Uncached Read 178.29 89.61 MB/sec [256K blocks]
Random 59.01
Uncached Write 20.37 2.16 MB/sec [4K blocks]
Uncached Write 261.11 83.59 MB/sec [256K blocks]
Uncached Read 105.47 0.75 MB/sec [4K blocks]
Uncached Read 185.54 34.43 MB/sec [256K blocks]
I use an Ubuntu CD to set AAM to level '254' (loudest - "performance")
Code:
Disk Test 72.90
Sequential 106.70
Uncached Write 189.92 116.61 MB/sec [4K blocks]
Uncached Write 181.89 102.91 MB/sec [256K blocks]
Uncached Read 50.58 14.80 MB/sec [4K blocks]
Uncached Read 143.77 72.26 MB/sec [256K blocks]
Random 55.37
Uncached Write 19.45 2.06 MB/sec [4K blocks]
Uncached Write 173.54 55.56 MB/sec [256K blocks]
Uncached Read 110.37 0.78 MB/sec [4K blocks]
Uncached Read 166.44 30.88 MB/sec [256K blocks]
How so??