Hi. i have or actually had the same problem, average speed from IDE to SATA was 5mbps. Then i tries to tune with hdparm and sdparm - nothing. But i noticed that I coudn't set to use UDMA mode (yeah, hdd support it), so i tried to set it in BIOS. BIOS saz that all settings is auto and it use the  fastest mode, udma5 on segate(5yrs old) an udma6 on hitachi (a few month ago). But after switchin from auto to udma5 and udma6 i get min 20mbps from ide to sata =) Dunno why, but it helps. Actually I have average speed from ide to sata ~30mbps, but I just mv 2gb, I should make some serius tests in it... later =) BTW, self-copy, move from one partition to another (on sata hdd) goes with the similar speed.

Yeah, one more thing, speed is very various, starts from 60-80 and goes down to 50 - 40 still there and goes ~17-25. Dunno why. Maybe my IDE is to slow for SATA.

Here is some data about my 
#sda = IDE, sdb-sata.
#motherboard ASROCK P4DUAL 915GL (nop, it is old 1-cpu mb =)), 1024 + 256 DDR1(tuned to 2.5-3-3-4, IIRC=)),

#CELERON D 2.4 (works on 2.7, I've overclock bus from 133 to 150)

root@lhome:~# lspci |grep IDE
00:1f.1 IDE interface: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) IDE Controller (rev 05)
00:1f.2 IDE interface: Intel Corporation 82801FB/FW (ICH6/ICH6W) SATA Controller (rev 05)

root@lhome:~# uname -a
Linux lhome 2.6.20-15-generic #2 SMP Sun Apr 15 07:36:31 UTC 2007 i686 GNU/Linux

root@lhome:~# hdparm -i /dev/sda

/dev/sda:

 Model=ST340810A                               , FwRev=3.99    , SerialNo=5FBBPX4Y
 Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs RotSpdTol>.5% }
 RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4
 BuffType=unknown, BuffSize=2048kB, MaxMultSect=16, MultSect=?16?
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=78165360
 IORDY=on/off, tPIO={min:240,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes:  pio0 pio1 pio2 pio3 pio4
 DMA modes:  mdma0 mdma1 mdma2
 UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5 udma3 udma4 *udma5
 AdvancedPM=yes: unknown setting WriteCache=enabled
 Drive conforms to: Unspecified:  ATA/ATAPI-1 ATA/ATAPI-2 ATA/ATAPI-3 ATA/ATAPI-4 ATA/ATAPI-5 ATA/ATAPI-6

 * signifies the current active mode

root@lhome:~# hdparm -i /dev/sdb

/dev/sdb:

 Model=Hitachi HDT725050VLA360                 , FwRev=V56OA7EA, SerialNo=      VFK401R41K57XK
 Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
 RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=52
 BuffType=DualPortCache, BuffSize=15315kB, MaxMultSect=16, MultSect=?16?
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=268435455
 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes:  pio0 pio1 pio2 pio3 pio4
 DMA modes:  mdma0 mdma1 mdma2
 UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5
 AdvancedPM=yes: disabled (255) WriteCache=enabled
 Drive conforms to: ATA/ATAPI-7 T13 1532D revision 1:  ATA/ATAPI-2 ATA/ATAPI-3 ATA/ATAPI-4 ATA/ATAPI-5 ATA/ATAPI-6 ATA/ATAPI-7

 * signifies the current active mode

root@lhome:~# hdparm -tT /dev/sda

/dev/sda:  #yeah. it really slow
 Timing cached reads:   1624 MB in  2.00 seconds = 811.40 MB/sec
 Timing buffered disk reads:   82 MB in  3.06 seconds =  26.79 MB/sec


root@lhome:~# hdparm -tT /dev/sdb

/dev/sdb:
 Timing cached reads:   1602 MB in  2.00 seconds = 800.85 MB/sec
 Timing buffered disk reads:  232 MB in  3.02 seconds =  76.90 MB/sec

have fun, i hope it helps somebody=)