Question why these X8 DVDs only burn at X4

[jimdagys]

In the past, I bought Chinese blank DVDs that were marked X8, and when I use Nero 6 to burn, X12 comes up as the default, which I can change to X8. However, recently, I bought the same Banana brand (but different graphic design) that is marked X8, but using these disks, Nero only allows me to burn at X4. The disks burn and seem to play fine, but my question is: Why do these newer disks that are marked X8 only burn at X4? What aspect of the disk tells the burner what speed is allowed? Older disks can still be burned at X8. Might these newer disks have some other "hidden" shortcoming?
Part of Nero log:
5:00:41 PM #12 Text 0 File DlgWaitCD.cpp, Line 2316
Recorder: PIONEER DVD-RW DVR-112, Media type: DVD-R
Disc Manufacturer: MCC 02 - RG20
Disc Application Code: 64, Disc Physical Code: 193
Complete Nero log for 1 burn on these newer disks is here:
http://rapidshare.com/files/252089194/nerolog.txt.html

[redwudz]

Just because they have the same manufacturer code, they may not be made at the same plant or with the same machinery or with the same quality control. That's a big problem with some brand discs. I have even seen them vary in quality within a spindle.

What finally controls the speed of burning is the Power Calibration Burn. This is done before every burn in a special area near the center of the disc. If that burn says 4X is all your burner can do with that media, then that's it. Sometimes a firmware upgrade can help if the discs are substantially different than the ones you used before. If your burning laser or your PS is a bit weak, that can also cause this, though most times you will get a power calibration error if the problem is serious.

I would just burn them and 4X and wait a little longer if they work at that burn speed.

EDIT: The only odd thing I spotted in that Nero log was the multiple 'Queue again later' lines. Not sure what that's about unless something in the PC is interfering with the transfer of the data to the burner. Was that disc burned from the hard drive or was it a direct copy from a existing disk? It did show a successful burn and if the disc works properly, maybe not a big problem.

[jimdagys]

I always burn directly from the hard drive. These disks show up as X4 before I click the burn button. I insert the disk, start Nero, add the DVD folder and Nero immediately shows only X4 as available. The only other time I have seen X4 as the only option is when I use DVD reburnable disks. The DVD reburnable disks I have used always burn at X4. Nero must sense something about the disk right away, because if I don't insert any disk, then Nero burn speed says "maximum", instead of a number.

[V Bot]

Now where did you say these discs were made? Personally, I burn at 2x, it makes for safer burning, less chance of a bad disc.

[MysticE]

Now where did you say these discs were made? Personally, I burn at 2x, it makes for safer burning, less chance of a bad disc.

Not true. Today's modern burners and discs are not meant or optimized to burn at such archaic speeds.