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Some customers have reported that version 2.61 of HD Tach* (utility created by TCD Labs*, Inc.) reports high 'CPU utilization' when the Intel® Ultra ATA Storage Driver is installed. After further investigation of HD Tach version 2.61, the producers of HD Tach indicated to Intel that the tool is targeted as a disk and driver tuning tool and not necessarily as a benchmark for grading the real-life 'CPU utilization' of a storage driver. Listed below is the technical explanation of why the 'CPU utilization' is reported as higher in HD Tach version 2.61 when the Intel Ultra ATA Storage Driver is installed:
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.
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