I have got similar results:That'll be because the buffer cache resides in memory and not on disk then :-) You have an 800MHz frontsize bus I would imagine.
hdparm -tT /dev/hde
/dev/hde: Timing buffer-cache reads: 128 MB in 0.13 seconds =984.62 MB/sec Timing buffered disk reads: 64 MB in 1.15 seconds = 55.65 MB/sec
This is with (probably) the same 120GB Seagate SATA drive. I doubt if
the first value is accurate though. It surpasses the maximum SATA speed
by a long shot..;-)
jch