In the following tests, we check the DVD reading capabilities of the HP 840b drive with scratched / defective DVD media. For our tests, we used CDVD Benchmark and Nero CDSpeed . The reference test media comes from ALMEDIO.

ABEX TDR-821

This is a single sided, single layer DVD-ROM with a 4.7GB capacity, and its surface has an artificial scratch varying in dimensions from 0.4 to 3.0 mm.

The following transfer rate picture comes from the CDVD Benchmark v1.21 transfer rate test.

Very smooth reading, with no drops in speed although the drive did not reach 16X max reading speed, which is the maximum supported speed with SL media, since the test media is a DVD-Video disc.

ABEX TDR-825

This is also a single sided, single layer DVD-ROM of 4.7GB capacity. The data structure of the disc is exactly the same as that of the TDR-821, the only difference being that there are no scratches on it. Instead, there are defective areas, ranging in dimensions from 0.5 to 1.1 mm.

There are also fingerprints sized between 65 and 75 micrometers.

In this case, the drive seems to have had a few problems from about the second defect onwards. Once more, only 12X max reading speed was achieved.

- Dual Layer media

ABEX TDR-841

This is an 8.5GB dual layer single sided DVD-ROM disc with artificial scratches ranging in dimension from 0.4 to 3.0mm, on both layers.

Both layers were read succesfully, without any drops in speed. Excellent performance with this type of media from the HP-840b drive.

ABEX TDR-845

The disc is a single sided, dual layer DVD-ROM disc of a 8.5GBcapacity. The only difference between the TDR-845 and the TDR-841 is that the former includes defective areas and fingerprints.

The dimensions of the defective areas range from 0.5 to 1.1 mm and the fingerprints are sized from 65 to 75 micro meters.

Again, no errors were reported, while the reading was smooth over both layers.

ABEX TDV-541

The TDV-541 is a single sided, dual layer DVD-VIDEO disc, with a capacity of 8.5GB. The disc is based on the TDV-540 series which was designed to inspect and adjust DVD-VIDEO players. The disc checks the layer switch operation from layer 0 to layer 1 and also includes test pictures and test signals on DVD sound files.

The current TDV-541 also checks the error correcting capabilities of the drive. It also includes scratches from 0.4 to 3.0 mm.

Very good error correction capabilities, smooth graph all the way to the end of the test.

ABEX TDV-545

The TDV-545 disc is based on the TDV-540 series. It is a single sided, dual layer DVD-VIDEO disc with a capacity of 8.5GB. The TDV-545 includes artificial black dots on the data surface, sized from 0.4 to 1.0 mm. It has also 65 - 75 micro meter fingerprints.

Same performance as with the previous media. The 545 test media was no match for the drive's error correction mechanism.

- Summary

Overall very good DVD error correction mechanism. All tests were completed without errors. The only drawback wsa that the drive never managed to achieve 16X max reading speed.