Poor performance with Seagate ST3500630AS part number 9BJ146-308

Has anyone had problems with performance of the
Seagate Barracuda 7200.10 500 Gbytes ST3500630AS P/N 9BJ146-308 ?

I have no problems with the earlier revisions of the drive, such as
P/N 9BJ146-305,
but the latest revision, which is the -308 revision, which has
firmware 3.AAK
runs at a maximum speed of only about 53MB/second using
HD Tune 2.53. HD Tach RW version 3.0.1.0 does not show the problem.

The earlier revisions of the drive run at a rate that depends on
the location of the data on the drive, starting at about 73MB/second
near the outer edge of the drive, down to about 38MB/second at the
inner edge.

With the -308 version, the rate starts at and remains at about
53MB/second until the point where the earlier versions of the drive
ran at less than 53MB/second. The rate a various positions of the
latest revision matches the older versions' rates at the corresponding
positions.

It is possible that the two benchmark programs use different disk
commands, which would explain why the two benchmark programs show
different performance.

I think the problem is in the microcode for the drive, and I am
trying to find out if the problem also depends on my hardware
configuration.

I have tried many -304 and -305 drives and they all get the
same performance, which shows the rate dropping gradually across the
surface of the disk with both benchmark programs.

The 3 -308 drives that I have tried show the same performance slope as
the -305 when using the HD Tach RW version 3.0.1.0.

However, the 3 -308 drives that I have tried all show about
53MB/second across about 2/3 of the drive, and then dropping gradually
when I use the HD Tune 2.53 benchmark.

I am running Windows XP Professional with Service Pack 1 on
my Gateway 700S with a 2.4GHz Pentium 4 and using an
ADSA4R-E 4-Port eSATA PCI Controller.

Seagate has been nice enough to replace the first two -308 drives with
refurbished -305 drives, but I have 5 more drives to replace that
they seem reluctant to, perhaps because they don't have any -305's in
stock anymore.

If other people have the problem it might be possible to get Seagate
to make a new part and/or firmware revision to fix things.