disk speed regression kernel 2.6.29 and after

[will]

I had been using an old 2.6.22 kernel on my machine, and I often backup one partition 
of my main hard drive to a partition on a second hard drive. The main hard drive is 
sata 640 gigs, and the second is a pata 320 gig. copying this partition from one 
drive to the other with dd takes about 3 minutes and 30 seconds. When I installed 
kernel 2.6.30, and 2.6.31, the time took 9 minutes and 20 seconds. I decided to go to 
the trouble of compiling all the kernels between, and kernels 2.6.22-2.6.28 all do 
the operation in about 3 minutes and 30 seconds. 2.6.29- newer all take about 9 
minutes and 20 seconds. The partition is 16 gigs. each drive seems to be as fast as 
before otherwise, it's just much slower copying from one drive to another, which I do 
very often. This is an nforce 3 based motherboard, amd southbridge, i think, with 4 
gigs of ram, athlon 64x2. 32 bit kernel. has anyone heard of this problem?
I currently have 3  hard drives hooked up.
a 200 gig on a promise controller,
a 320 gig on the amd pata?
a 640 sata on the nv i think.
The motherboard is a Asrock-AM2NF3-VSTA
copying this partition with dd or cat or schily's dd between any of these 3
different hard drives takes different times depending on the speed of the drive with
kernels 2.6.22-2.6.28, but takes about 9 minutes and 30 seconds on any of the drives
with the kernels 2.6.29 and after.
Please cc me with any followups or anything. thanks.
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