3 - Basic Tests - Benchmark Transfer Rate Test
This test measures transfer speed of data and shows results in a graph. In other words, it shows reading speed of data from a disc. This test can be done for two main reasons:
- To test a drive (reader or burner)
- To test a burned media (CD or DVD)
If the main purpose is to test a drive, can be used some special discs containing standard defects, like A-BEX discs.
If the main purpose is to test a burned media, the test is aimed at verifying that burning was done correctly and that the media is readable and all data retrievable.
In this test are showed two lines. If colors were not modified by the user, there will be a green line that represents transfer speed, and a yellow line that represents disc rotation speed in revolutions per minute (RPM).
In the bottom scale there is disc capacity, in Megabytes (MB) for CD media and in Gigabyte (GB) for DVD media. In the left scale there is reading speed, and in the right scale there is disc rotation speed (in RPM x 1000).
Under the graph there is a little window containing some extra informations on running tests. For example are reported date and time, test type, reading type, etc.
On the right of graph there is a group of four boxes containing results of Transfer rate Test (TRT):
Current: The current speed during test execution. When test ends, this box changes name and becomes "
Average", i.e. the mean value calculated from maximum and minimum values recorded in the entire test.
Start: The lowest speed detected in the entire TRT. If the reading curve is regular, this value is the same of the starting speed; if the curve is irregular, this is the lowest value recorded in the entire test (see picture).
End: The highest speed detected in the entire TRT. If reading curve is regular, this value is the end speed; if curve is irregular, this is the highest value recorded in the entire test (see picture).
You can see in that picture with an irregular graph, that TRT starts around 7x speed, and ends around 9x speed. In the
Start box is shown 1.83x and in the
End box it's reported 13.89 x. These are, respectively, the minimum and the maximum detected speeds in the entire TRT. These values are used to calculate the "
Average" speed.
Type: TRT doesn't measure only
reading speed, but also the
reading type. There are different modes to read a disc. To understand these modes, it's important first to describe some basic notions: "Linear Speed" and "Angular Speed".
In this image the black arrow is the optical pickup route, and the three blue arrows are three different parts of the disc. Each blue arrow represent a segment of a disc track read by optical pickup. All segments run along the same
angle, in our example 90°, but from the image is clear that segments (tracks) in the more peripheral parts of the disc run along a longer
linear distance: 1 cm inner track, 5 cm intermediate track, and 10 cm external track. In the picture all values are given only as an example, and are not absolutely exact.
"
Angular speed" is the amount of
angle ran along in the time unit when the disc rotates. If a disc rotate at a constant speed,
angular speed is constant too, because every part of the disc run along the same amount of angle.
"
Linear speed" is the amount of
length ran along the time unit when disc rotates. If disc rotates at a constant speed, linear speed vary according the distance from the center of disc. The most inner parts of the disc, near center, run along the shortest distance, and then have the lowest
linear speed. The most external parts of the disc, instead, have the highest
linear speed because they run along the longest distance.
In optical drives, disc reading starts from the center and goes externally when pickup is moved along a radius of the disc (the black arrow in the picture). If rotation (angular) speed is constant, the most internal tracks run at the lowest linear speed (i.e. are read at the lowest speed), and linear speed increases progressively toward the external parts of the disc (i.e. reading speed increases toward the external).
Optical drives can use four different reading types: CLV, CAV, P-CAV, e Z-CLV.
CLV (Constant Linear Velocity): Reading speed is constant in all disc parts. This means that when a disc rotates tracks run along the same linear distance. Consequently, when optical pickup moves toward external parts of disc, rotational speed is reduced progressively.
CAV (Constant Angular Velocity): Rotation speed is constant and reading speed increases progressively from the center toward external parts of the disc.
P-CAV (Partial-CAV): Rotation speed is constant and reading speed increase progressively up to a certain value. From here, reading speed remains constant, and rotation speed decreases progressively.
Z-CLV (Zoned Constant Linear Velocity): Usually this type is used for writing on a disc more than reading. In this type, writing speed is constant for a given segment of the disc, then increases to write another segment, and so on up to the end of disc.
In each segment, linear (writing) speed is costant, and angular (rotation) speed is progressively reducing; at the end of first zone, rotation speed is increades to allow writing at a higher speed, and so on up to completion of disc writing.
In "
Benchmark" window, after inserting a disc in the drive, are showed two other pieces of informations: disc type and its capacity.
For example, inserting an audio disc in these boxes will appear "
Audio CD" and disc duration. Inserting a video DVD, will be showed "
DVD-Video" and disc capacity in GB. Inserting a burned disc, according to selected settings in global options of CD-DVD Speed, will show the disc type (+R/RW, -R/RW, blank media) or disc booktype (+R/RW, -R/RW, or ROM).
To avoid confusion, remember what settings were selected. If in options is selected to show disc type, a +R disc with changed booktype to ROM will be still showed as +R.
Finally, according to the disc type loaded in the drive, the Transfer Rate Test will show different results.
Data disc (CD or DVD): TRT measure data reading speed.
If the data disc is a dual layer DVD, graph will show two more colored vertical lines. Red line is total disc capacity, and fucsia line is the layer transition. This latter line divides the graph in two parts, and each part is the the reading of a disc layer.
Audio CD: TRT measure Digital Audio Extraction (DAE) Speed.
Blank disc: inserting a blank media it's measured the writing speed. Writing test will be described in more detail later.