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Intel Customer Support Common System Configuration Issues using Intel® Ultra ATA Storage Driver 38
The HD Tach utility (version 2.61) measures how much the processor is utilized during a timed
disk Input/Output (I/O) transfer loop by comparing how many loops of an integer math routine
are run when the I/O transfer is taking place versus how many of the same integer math loops
are run in a similar timed run without the disk I/O operating. The HD Tach utility then generates
a processor overhead percentage based on the difference of the two idle loop count runs. The
HD Tach 'CPU utilization' results are a worst-case scenario based on continuous drive
operation, which in real-world situations happens quite rarely. Even during the running of highly
disk-intensive benchmarks, such as WinBench* Disk WinMarks*, the disk is only accessed
around 30% during the timed test. As a result, the HD Tach utilization report truly is a worst-
case scenario.
Note however that this is not indicative of the actual processor usage of the Intel Ultra ATA
Storage Driver compared to typical operation where application and driver time are factored in.
The 'CPU utilization' for Business Winstone*, or other business application-based benchmarks,
report a much lower 'CPU utilization' number. When 'CPU utilization' for the rest of the
operating system and applications are factored in, the Intel Ultra ATA Storage Driver accounts
for a much smaller increase in 'CPU utilization' than the HD Tach utility reports.
The Intel Ultra ATA Storage Driver does implement features in the driver that, while it may show
higher 'CPU utilization' in utilities such as HD Tach, does enhance performance on the system
by working more effectively with hard drives to reduce the overall latency and bandwidth
required to do the required disk I/O.