7200 RPM udma33 same speed as 5400 PIO mode 4

[Rick Macdonald <rickmacd@home.com>]

I added a Maxtor 27GB 7200rpm ATA66 drive to my P200MMX when I upgraded to
potatos and kernel 2.2.14.

My motherboard (ASUS TX97-E) only supports udma mode 2 (33MB/sec), but I
find that this drive and my old WD 4GB (no UDMA) both show the same speed
of about 9.4MB/sec with hdparm -t. Even if the new drive is the only drive
on the primary IDE interface.

All the boot messages and hdparm info seems to indicate that the UDMA-2 is
recognized, but why don't I see any speed difference?

Here is the output of hdparm -v -i for both drives:

/dev/hda: (MAXTOR 27GB, UDMA)

 multcount    =  0 (off)
 I/O support  =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 nowerr       =  0 (off)
 readonly     =  0 (off)
 readahead    =  8 (on)
 geometry     = 3322/255/63, sectors = 53369568, start = 0

 Model=Maxtor 92732U8, FwRev=RA530JN0, SerialNo=H8059G4C
 Config={ Fixed }
 RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=57
 BuffType=3(DualPortCache), BuffSize=2048kB, MaxMultSect=16, MultSect=off
 DblWordIO=no, OldPIO=2, DMA=yes, OldDMA=0
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=53369568
 tDMA={min:120,rec:120}, DMA modes: mword0 mword1 mword2 
 IORDY=on/off, tPIO={min:120,w/IORDY:120}, PIO modes: mode3 mode4 
 UDMA modes: mode0 mode1 *mode2 mode3 mode4 


/dev/hdb: (WD 4GB, no UDMA)

 multcount    =  0 (off)
 I/O support  =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 nowerr       =  0 (off)
 readonly     =  0 (off)
 readahead    =  8 (on)
 geometry     = 969/128/63, sectors = 7814016, start = 0

 Model=WDC AC34000L, FwRev=24.39E26, SerialNo=WD-WT3510356735
 Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq
}
 RawCHS=7752/16/63, TrkSize=57600, SectSize=600, ECCbytes=22
 BuffType=3(DualPortCache), BuffSize=256kB, MaxMultSect=16, MultSect=off
 DblWordIO=no, OldPIO=2, DMA=yes, OldDMA=0
 CurCHS=7752/16/63, CurSects=7814016, LBA=yes, LBAsects=7814016
 tDMA={min:120,rec:120}, DMA modes: mword0 mword1 *mword2 
 IORDY=on/off, tPIO={min:160,w/IORDY:120}, PIO modes: mode3 mode4 

...RickM...