The performance value of the hard disk can be calculated differently (like the health value). The calculation method option on the advanced options panel defines the method used to calculate performance value also.
Hard Disk Sentinel combines different values to determine this value. The raw values of performance related S.M.A.R.T. attributes (for example, seek time) affect the overall performance by maximum 25%. The number of data transfer errors (ultra ATA CRC errors) found in the last month may also reduce the performance value by 25%. These transfer errors are not really indicate the problem of the hard disk, but they can decrease the stability and performance of the system.
The rest 50% of the performance value is calculated by examining the currently used DMA transfer mode and the maximum available transfer mode. If the hard disk works only in PIO (programmed I/O) mode, this part of the condition value is 0 instead of 50.
For example: if the transfer rate is only Ultra DMA mode 2 (33 MB/s) instead of its maximum available transfer rate Ultra DMA mode 5 (100 MB/s) but the performance related S.M.A.R.T. attributes are correct and no data transfer errors found in the past month, the overall performance value will be 25 + 25 + (2/5) x 50 = 70 %. In this example, the problem is probably caused by using an old IDE cable with only 40 wires.
If this option is selected, the performance-related S.M.A.R.T. attributes are evaluated. All such attributes will have a value calculated between 0 and 100% based on the actual value, the threshold and the theoretical maximum value (the latter is determined by Hard Disk Sentinel based on the manufacturer and model). Multiplying these values will give the overall performance value of the hard disk condition.