Test machine:

For this article we will be using a computer with the following configuration:

Hardware:

• Motherboard: Asus A8V Deluxe
• Processor: AMD Athlon 64 X2 4400+ (Toledo)
• RAM: 1 GB Corsair Kit PC3200 DDR
• GFX: MSI GeForce 6600 GT
• Sound: Onboard Realtek AC\’97
• Hard disk: Maxtor 6V300F0 300 GB (S-ATA)

Installed Software:

Windows XP Professional XP Professional is installed on the computer along with Service Pack 2 for Windows XP. We will be using the following software in this article:

• Nero CD/DVD Speed
• PlexTools Professional  
• KProbe v2.5.2

Test Drives:

In this article we are going to use the following drives:

• BenQ DW1655 – Firmware BCIB
• LG GSA-H22L – Firmware 1.00
• Lite-On SOHR-5238S – Firmware 4S09
• Lite-On LH-18A1P – Firmware GL0B
• Optiarc AD-7173A – Firmware 1-01
• Plextor PX-760A – Firmware 1.05

Testing methods:

We will write five media on five different burners at the highest supported speed, even though the media itself is rated at 40x.

We test CD media in two different ways. The first way is to look at how much error correction has to take place in a drive when reading the disc; this is also known as Disc Quality Scanning. The second way is to test whether the disc can be read at full speed without any slowdowns; this is also known as Read Transfer Testing.

In this review we perform Disc Quality Scanning on three different drives instead of using just one drive, and the reporting behaviour of the three scanning drives is very different. This makes it more complicated to interpret the results, but it also provides us with a more thorough understanding of how the media behaves instead of the limited view possible by only using a single scanning drive.

Disc Quality Scanning – C1/C2 (and CU):

CDs use an error detection and correction system (CIRC) which is usually transparent to the end-user, but we can get an idea of the "quality" of a disc by  performing Disc Quality Scanning which shows how many errors the drive is detecting and correcting behind the scenes.

There are two layers of error detection and correction on all CD media; these are called C1 and C2. Data CDs also have a third layer of error detection/correction.

There is more than one way to handle C1 and C2 error detection/correction, but a simple and common way is to detect and correct up to two errors per frame in each stage and detect three or more errors:

• E11: 1 error detected and corrected by C1 layer
• E21: 2 errors detected and corrected by C1 layer
• E31: 3 or more errors detected but not corrected by C1 layer

The sum of these (per second) is called the BLock Error Rate: BLER=E11+E21+E31

• E12: 1 error detected and corrected by C2 layer
• E22: 2 errors detected and corrected by C2 layer
• E32: 3 or more errors detected but not corrected by C2 layer

Any E31 is uncorrectable by the C1 layer and will result in the bytes in that frame being redistributed into multiple frames which are passed to the C2 layer.

Any E32 is uncorrectable by the C2 layer and will result in interpolation being used for Audio CDs or will result in third layer error correction being used for Data CDs.

Different drives have different ways of reporting these Exy errors in a Disc Quality scan. The drives used in this review report Exy as follows.

Lite-On SOHR-5238S:

• C1=BLER=E11+E21+E31
• C2=E32

Plextor PX-760A:

• C1=BLER=E11+E21+E31
• C2=E22
• CU=E32

BenQ DW1655 Disc Quality:

• C1=BLER=E11+E21+E31
• C2=E32

BenQ DW1655 Advanced Disc Quality:

• All Exy errors are reported separately as well as BLER=E11+E21+E31

We want to see as low error numbers as possible. Any E32 at all are unacceptable. Any E22 are undesirable. BLER should be no more than 220 (per second).

Read Transfer Testing:

By attempting to read the disc all the way from start to end we can verify that it\’s actually readable. By reading it at full speed and looking at the read speed graph, we can test whether the drive has any problem reading any part of the disc. What we want to see is a perfectly smooth graph without any slowdowns.

Summary:

By using two different testing methods, i.e. Disc Quality Scanning and Read Transfer Testing, we get a good idea of how the disc performs. By using three different drives for Disc Quality Scanning we get an even better understanding of how the disc performs in different drives.

Since all the tests are a result of the interaction between the drive and the disc, there is no "wrong" answer in the tests. The tests are different and equally valid views of the disc.

Any truly excellent disc should show good results in all the used tests.

On the next page – we are going to test the media on the BenQ DW1655…