CDROM METRICS

3/22/97

CDROM Metrics are measurements used to quantify CDROM Performance. Typical metrics are:

Read Data Transfer Rate: A measurement of how fast data can be read sequentially from a CDROM. Typically the data will be read several times and the observed read rate is then averaged. Reads should be performed in all parts of the CDROM in order to account for rotation speed variations. Data rates are measured as data after framing and error correction bits have been removed. Data rates will typically be 150 KBytes per second times the X rating of the drive. For example a 4X drive should read about 4*150 = 600 KBps. A "Multimedia" drive should deliver in excess of 550KBps.

Write Data Transfer Rate: CDROM size divided by duplication time. This will typically be about half the read rate.

Duplication Time: A measurement of the total time required to copy a CDROM. Different types of data should be included in the test CDROM, and the measurement should indicate whether set up and close times are included.

Average Access Time: The average time to access information on a CDROM. Values vary from nearly 500 milliseconds to less than half that

CPU Load: A measure of the percentage of CPU loading while reading a CDROM. Acceptable values are considered to be 7% for Win95 or 40% for Windows 3.11. Measured values under Win95 vary from 4%-5% to about 50%.

Error Rate: The number of errors reported when reading a deliberately damaged disk. The damage typically would include both scratches that cause random errors and obscuring patches that cause burst errors in longer sequences of bits. Surprisingly, drives differ substantially in their error correction capabilities.

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