There are four specifications we are looking at here. The drive rotation
speed (7,200 RPM in this case) affects the latency - the delay before
the desired sector is accessible. The faster the rotation, the less time
it takes to reach the data.

Next there is the data transfer rate. This is what the ATA/100 or
ATA/133 refers to. Of course, this is also affected by the rotational
speed. In most cases, the ATA transfer speed is much higher than the
drive can sustain - it is a momentary burst rate speed that the drive
can achieve only for a short time.

The seek time (e.g. 9ms) tells us how fast the read/write head can move
into position on the desired cylinder (track). This has nothing to do
with transfer rate or rotational speed.

The last item that can affect performance is the size of the buffer.
This buffer is some RAM that is part of the drive electronics and can
make the drive look faster than it is mechanically but providing the
data from drive RAM rather than waiting for the actual reading of the
disk. This works only if the desired data happens to already be in the
buffer - often this can be the case, hence the improved performance with
a larger buffer.

Hope this helps and does not confuse anyone further.

Peter
------------------
The NoSpin Group
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-----Original Message-----
Looking at Maxtor UltraATA/133 with 2mb buffer at 7,200 RPM with seek
time <9.0ms for $129. Compared to Western Digital UltraATA/100 with 2MB
buffer at 7200 RPM with seek time 9.5ms for $129. Spec are from Global
Computer August 2002 page 52. I would say the .5ms drop would be due to
the 133? Every thing else is the same?

Richard F. Bolha

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