Strange harddisk performance problem... or?

[ichtys|dk]

A couple of days ago I succeded in installing my first usable Gentoo Linux (second try), but after a while, I noticed a lack of performance (when I installed Gnome), and actually everything seemed very slow.

My system: Asus M2400N
1300Mhz Centrino Pentium M
256 Mb DDR 2100 ram
40 GB harddisk (5400rpm)

I ran a hdparm -tT /dev/hda, and got the following results:

/dev/hda:
Timing buffer-cache reads: 336 MB in 2.03 seconds = 165.52 MB/sec
Timing buffered disk reads: 12 MB in 3.13 seconds = 3.83 MB/sec

This seemed a little slow, and I asked for help in a danish linuxforum (http://www.linuxin.dk)

With the help from other members I tried a lot of things; Recompiling the kernel to ensure DMA support, Compiling a completely new kernel from Gentoo-sources (old one was vanilla), and i tried to run hdparm with these options:

hdparm -X69 -c3 -m16 -d1 -u1 /dev/hda

Now I get the following by typing hdparm -i /dev/hda:

/dev/hda:

Model=IC25N040ATMR04-0, FwRev=MO2OAD0A, SerialNo=MRG201K2G6PWKC
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4
BuffType=DualPortCache, BuffSize=1740kB, MaxMultSect=16, MultSect=16
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=78140160
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
AdvancedPM=yes: mode=0x80 (128) WriteCache=enabled
Drive conforms to: ATA/ATAPI-6 T13 1410D revision 3a:

* signifies the current active mode

Nothing has chaged... read speed is the same as before...

What can I do to solve the problem?