Plextor PX-716A burning/reading an 8x DVD+R disc at 16x speed;
PoweRec is on
 

The drive reached the maximum speed, but couldn’t finish the work at 16x. The PoweRec mechanism must have thought this operational mode unallowable with this particular medium and dropped the speed to 12x. The resulting disc was read without problems. Let’s try to disable PoweRec and see if the PX-716A can burn a similar blank at 16x speed.

Plextor PX-716A burning/reading an 8x DVD+R disc at 16x speed;
PoweRec is off
 

It works! There’s a sudden jump from 14x to 16x speed and the drive finished the burning at 16x. We’ve got quite an original burn algorithm here. It is not CAV, but it is not yet P-CAV as we’re accustomed to see it. But it is closer to P-CAV anyway. The Plextor PX-716A does behave curiously in this mode as I have never seen any other drive behave. The time difference in comparison with the previous case (with PoweRec) is only 6 seconds, which is a gain, although a very small one. Minor beats and slumps of speed are observable during the reading of the area written at 16x. Now let’s take a blank rated for 16x speed and enable PoweRec and study the outcome.

Plextor PX-716A burning/reading a TDK DVD+R 16x disc;
PoweRec is on
 

It’s the same as you’ve seen above, when the 8x blank was being burned with disabled PoweRec. The duration of the burn sessions coincides to a second, too. There are bigger slowdowns here, however, and they too fall on the area where the drive used 16x burn speed. Thus, although TDK rates these discs for 16x, the quality is better with 8x Verbatim (manufactured by Taiyo Yuden)! Now, the most curious part of this test is comparing the discs written in this mode.

Here’s a curious picture for you: the level of PI errors grows up when the drive reaches 16x burn speed. With disabled PoweRec, the burn speed is dropped down and this immediately leads to a reduction of the number of errors. So, I should acknowledge it was right for the drive to slow down in this case. Now take a look at what happens with disabled PoweRec: the drive is increasing its burn speed steadily and the PI error rate is growing exponentially, to 800-900, which is much higher than the highest allowable peak of 280. Although the quality of the resulting disc degenerates much, it is readable, although at a lower speed. And what about the blank which is rated for 16x burn speed? We’ve got the same increase of PI errors at the maximum speed, although it is not as dramatic as with the disc rated for 8x burning. The peak of PI errors is about 50-60 on the outermost tracks – that’s not small, but absolutely within the allowable limits. It remains a mystery, however, why there’s a bigger reduction of the read speed here (the number of errors is smaller).

Thus, we have the following totals of PI errors and failures with the three discs:

• 8x PoweRec On: 72,209 PI errors and 215 PI failures
• 8x PoweRec Off: 673,274 PI errors and 7,310 PI failures
• 16x PoweRec On: 55,742 PI errors and 1,079 PI failures

In the latter case the higher total of PI failures is due to the lower quality of the blank itself rather than to the transition to 16x speed. You can also see that disabling PoweRec permits to use higher burn speeds with low-speed media, but at what price! The totals of PI errors and failures become 9 and 34 times higher, respectively, while the time gain is only 6 seconds! I don’t think such a big quality loss is worth those paltry six seconds. But we’re continuing our investigation.