X-bit labs - Print version

We would like to introduce to you a portable optical burner, which may make an ideal companion not only for mobile but also for a desktop PC. The solution from ASUS boasts small dimensions, low weight, high burn quality and low level noise. Read more about its performance and burn quality in our detailed review!

External optical drives seem to be losing their appeal with every passing day. When a modern internal multi-format recorder can be got for less than $60, it is no big problem to equip even a low-end desktop computer with a DVD-burner. The cost of the optical drive won’t affect the total cost of the system much. Modern midrange and high-end notebooks all come out currently with DVD-recorders, too. There is of course the low-end sector left where combo-drives are traditionally used, but it is a specific feature of this market sector, especially as concerns mobile equipment, that the manufacturer has to save on virtually everything to reduce the cost of the end product.

As a result, it becomes ever more difficult to find an application for external optical drives even though they are still being manufactured. Thinking of one, I’d conjure up obsolete notebooks that are still quite capable of performing office tasks but require a small upgrade. One of the upgrade opportunities would be a replacement of the installed CD-ROM or DVD-ROM with a DVD-recorder. In this case it may be difficult to find an internal notebook drive in retail shops and inexperienced users may also find it problematic to install the drive into the notebook. As for desktop systems, the use of an external optical drive may be justifiable when it is undesirable to equip each workplace with a stationary drive due to money-saving reasons or to corporate security considerations. I could also imagine an unlikely situation when a user runs short of IDE ports and has to use an external DVD-burner just because he/she doesn’t want to get rid of the already installed IDE devices.

So, despite the widest popularity of internal drives, there can still be some situations, maybe not very common, when you may want an external optical drive. That’s why almost all leading makers of optical drives are still developing new models.

There are currently two approaches to making an external optical drive. The first approach is meant mostly for desktop systems users and involves putting an ordinary DVD-burner with the IDE interface into a plastic or metallic case with a power adapter and an IDE-USB or IDE-FireWire converter. This approach is not free from drawbacks. First, the resulting device is rather large and heavy (especially when you add the AC/DC power adapter), so you can call it external, but not portable. Of course, it’s no big deal to carry it over from one desk to another, but you won’t want to take this load with you on a long trip. On the other hand, the user can replace the drive with a more advanced one or in case of failure (the external casing can usually be dismantled and the upgrade procedure only involves connecting some cables). The user also receives all the advantages of a full-featured desktop drive, i.e. a fully protected optical unit that is going to work longer than a notebook drive’s, advanced error correction functions and a better driving mechanism.

You may have guessed the second approach – a small form-factor optical drive can be packed into a protective case, too. Smaller dimensions and weight are obvious advantages of this solution, and the result is also going to be more aesthetic, I think. But still, all the drawbacks of portable drives remain here: the open optical unit makes the user be very careful when putting a disc into the drive and avoid dust getting to the optical lens. Also, optical drives employed in notebooks are generally worse than their desktop counterparts at reading damaged media. On the other hand, the advantage of size and weight makes up for these deficiencies, especially if you use the device with proper care.

The SDRW-0804P model from ASUS belongs to this second class of external optical drives and is going to make the subject of this review.

Design and Functionality

The new generation of writing optics from ASUS is labeled with the SDRW index and comes to replace ASUS’s successful SCB series of external drives. It includes full-featured DVD-burners rather than combo drives of the notebook form-factor designed for external use.

Besides their main functional purpose, mobile accessories are supposed to express the taste or even the status of their owner. So, let’s give the drive an examining look.

The drive comes in a retail box (we haven’t yet seen OEM versions of devices of that class) that is filled with the following:

The drive looks cute in its stylish silvery case. The front panel of the device is silvery, too, with a nickel-colored Eject button. The controls and indicators are the same as you would expect to find on an optical drive.

ASUS has always been original about designing its external optical drives. For example, the SCB series models were shaped like a compact-disc case. The SDRW-0804P-D model follows this theme: there is a depression on the cover of the case which repeats the outline of the compact-disc. What’s nice, this solution is not only aesthetical, but functional, too. It is handy to put a disc there temporarily. The new design looks attractively overall.

The following can be found on the drive’s rear panel: a Power On/Off lever, a power connector (the design of this connector is similar to the charger connector on Nokia’s cell phones; it is reliable and prevents the plug from falling out of the connector at work), and two interface connectors. Unlike many other external drives, this model is equipped not only with USB 2.0, but also with a FireWire interface to give you more connection flexibility. At least, Mac users shouldn’t feel neglected.

The drive uses ASUS’s traditional technologies FlextraLink (buffer underrun protection) and FlextraSpeed (the drive automatically chooses optimal laser power and burn speed), but technologies that reduce noise and vibration (DDSS II and AFFM) are not implemented due to the design specifics of the new model. Instead, the user receives the Optical Pickup Head LCT function which improves burn quality with misbalanced media or media with an uneven surface.

Despite the tiny size, the SDRW-0804P-D has up-to-date characteristics. It supports almost all existing optical disc formats, including DVD+R DL. The relatively low write-once speeds are due to the design of the drive as well as to the interfaces employed.

I think I can finish the descriptive part of the review here. Just take a look at the information Nero InfoTool and DVDInfo report about the drive and we can proceed to our tests.

Performance in CD WinBench 99

We traditionally start out by checking the performance of the drive in the synthetic benchmark WinBench 99.

The new ASUS drive cannot match its “desktop” counterparts in speed: internal drives have a two or even three times better score here. This is not only due to the smaller speed formula of the ASUS SDRW-0804P-D, but also to its rather high access time of 164ms (slowest internal drives have an access time of 130ms or something). On the other hand, the ASUS is still fast enough for performing everyday tasks, and it is just incorrect to compare it with “desktop” drives. They just belong to two completely different categories of hardware. So, let’s better get closer to more important things, namely to the quality of the written discs. But first here’s another test of speed of the ASUS SDRW-0804P-D, this time using a CD-R disc recorded at the max burn speed:

The average seek time as calculated by this test does not differ much from the results of desktop drives, contrary to what we have seen in WinBench 99. 127 milliseconds is a good result, considering the class of the device (some models from TDK and Lite-On have a higher seek time). Talking about the ergonomic qualities of the device, the full disc recognition time is a good 15.5 seconds. This is comparable to the most leisurely desktop drives, but is a good speed for a portable optical drive. The burst data-transfer rate of 15MB/s is a consequence of the interface employed during the test, namely USB 2.0.

Performance during CD-R Media Burning

We used Verbatim Datalife 52x blanks for this test (Moser Baer India, MID: 97m17s06f).

It took almost 6 minutes to burn a blank at 24x, which is the maximum burn speed available with the ASUS drive. Desktop drives normally perform this task in about 4 minutes. Of course, there is an explanation of such a behavior of the ASUS drive, but I’ll offer it below when I will talk about the quality of the recorded discs. When the burn speed is lowered to 16x, the duration of the burn session grows up by 27 seconds only. It means the SDRW-0804P-D is still worse than desktop drives at 16x, but not as much as at 24x.

And now let’s see how the drive reads the disc it has recorded at the maximum (24x) speed:

The disc is read without problems: the graph is straight and clear, without any fluctuations or slowdowns. The maximum speed as declared by the manufacturer is successfully achieved. This is an indirect indication of high quality of the recorded disc. And the quality check is the next thing I’m going to do.

So, you can see now why the new drive from ASUS is much slower than internal IDE drives at writing CD-Rs at 24x speed: it just uses a four-step Z-CLV algorithm, while IDE drives use either P-CAV or single-step Z-CLV. Otherwise, the burn process was completed without problems.

Despite the high density of the first encoder errors, the average BLER is no higher than 10 which is itself an indication of a very high quality of the disc. The total number of C1 errors is rather high (21,442), but the average (10) and maximum (20) BLER is good anyway. There are two minor surges of C2 errors, but I’m inclined to regard them as defects of the blank rather than errors of the drive. All in all, the results are very satisfactory, especially as we deal with a portable drive with all the consequences.

The Beta/Jitter graphs are another confirmation of the high quality of the disc: the Beta graph is an ideally straight horizontal line going at the zero mark and the Jitter rate is uniform along the surface of the disc, too.

You can see that the ASUS uses a two-step Z-CLV algorithm at 16x speed, while internal IDE drives usually employ the classic CLV. It explains the difference of about one minute in the burn session duration between them. Otherwise, the ASUS recorded the CD-R without problems. But what about quality?

That’s an admirable performance! The total number of C1 errors has diminished from 21,442 to 14,511. The average BLER is about 5-6, and the maximum level of BLER is about 15, if we don’t count in the single spikes that reach 20. Second encoder errors are missing altogether. The Beta graph is still an ideally horizontal line lying at the zero mark, and the uniformity of Jitter is good, like in the previous test. As you can see, the quality of the disc improves noticeably at the reduced burn speed.

Summing up the results of the ASUS SDRW-0804P-D with recordable CDs, I should acknowledge it performs well at both maximum and the reduced burn speed. Yes, some models (not many, though) of internal optical drives burn CD-Rs a little better, but we should keep it in mind that we’re talking about a portable drive with a weaker optical section.

Performance with CD-RW Media

This section is about how the SDRW-0804P-D handles rewritable CDs. The drive took 5 minutes and 43 seconds to produce a recorded CD-RW disc at 24x burn speed. Internal drives accomplish this in about 3 minutes and a half. So, the ASUS is again considerably slower than desktop optical drives. Let’s check the quality of the resulting disc and see where this slowness comes from.

Just like when burning a CD-R at 24x speed, the drive uses a four-step Z-CLV algorithm here which accounts for the slow burning. But speed is not the main parameter in the process. Let’s better check the quality of the resulting disc.

The results are good overall. The total number of C1 errors is rather high (49,934), but this is a rewritable medium and we shouldn’t be as strict about it as about write-once CDs. The average BLER is no higher than 25, except the outermost tracks of the disc where it goes up to 70. This latter surge isn’t lengthy and will hardly affect the readability of the disc. C2 errors are missing altogether. The Beta graph is almost ideal, like with the CD-R media. Jitter is uniform along the entire disc, except a small stretch on the outermost tracks where there’s the surge of C1 errors.

Thus, the ASUS SDRW-0804P-D processes rewritable CDs well enough. To finish the CD-related section of this review I’m going to evaluate the error correction capabilities of the drive.

Reading Bad CD-ROM Discs

The drive read the test disc through in 14 minutes and 56 seconds and couldn’t read 8 data blocks. This is a poor result if we compare it to full-featured internal IDE drives. As you can see, portable optical drives for notebooks have a weaker optical system and a worse error-correction mechanism than their desktop counterparts.

Reading damaged discs isn’t a strong point of the ASUS SDRW-0804P-D, but only when the disc is really very bad. The drive handles medium-quality discs quite well.

So, the CD tests give us positive results: the quality of writing and rewriting is highest. The only thing I may complain about is the rather poor error-correction mechanism. On the other hand, this is natural for a portable optical drive.

Reading DVD Discs

The drive read the single-layer medium quite well, save for the very end of the disc where it lowered its speed from 8x to 6x. Thus, the drive reached the maximum declared speed but couldn’t keep it to the end. Reading the dual-layer DVD-ROM was not accompanied with problems – the graph is clear and straight, without any fluctuations of speed.

DVD Media Burn Quality

DVD-R: The ASUS SDRW-0804P-D burns DVD-R discs at 4x speed in about the same time as internal IDE devices do, the difference being no more than 1 minute. The gap becomes bigger at 8x speed. It is 5 minutes, which is quite a lot. You may take a guess at the cause of this difference if you recall the tests with CD-R and CD-RW media, but I’ll talk about it later on.

DVD+R: Like with the DVD-R format, the ASUS drive is comparable to “desktop” drives at 4x, but at 8x speed the difference amounts to 4-5 minutes. Of course, this difference is due to the employed burn algorithm, but we’ll talk about it later.

DVD-RW: There are no surprises here. There is a difference at both 2x and 4x if we compare the ASUS with desktop drives, but this difference is not more than 1 minute. Internal IDE drives may differ as much among themselves, too.

Now let’s examine the quality of DVD media this drive produces. Write-once formats come first.

Single-Write (Non-Rewritable) Media

The drive had no problems during the burn process; there were no fluctuations or slumps in speed. We can see a couple of curious things, though. First, the diagram shows clearly that notebook drives of the last generation support Running OPC when recording DVD media. Second, the ASUS doesn’t follow the tradition again and uses a two-step Z-CLV burn algorithm instead of the typically employed CLV. The length of the first step is small, however, and the drive is close to CLV-using models as concerns the duration of the burn session.

The quality of the resulting disc is very high. This total of PI errors (13,797) would be good even for desktop drives, not to mention mobile ones. The average rate of PI errors is not higher than 5, with single spikes of no more than 8-9 errors. The rate of PI failures doesn’t exceed 2.

The Beta graph isn’t exactly ideal at the part of the disc where the drive hasn’t accelerated to 4x speed yet: you can see separate “steps” indicating the drive’s searching for the optimal laser power. The Jitter rate isn’t uniform there, either, but as soon as the drive hits 4x speed, both parameters become normal and blameless.

The results of the TA Test agree as to the high quality of the recorded disc. Jitter is low; the only problem is the Peak Shift value: the average length of pits and lengths doesn’t match the standard. The drive makes the pits shorter than they should be, so the lands turn to be a little longer than necessary.

So, here’s why the ASUS SDRW-0804P-D is slower than desktop drives at burning discs: like with CD-Rs, it uses a four-step Z-CLV algorithm instead of P-CAV or two-step Z-CLV. This leads to the drive’s being 4-5 minutes slower than desktop models at burning discs at 8x speed. Otherwise, the burn operation was completed successfully.

The quality of the resulting disc is quite right. The average PI error rate is below 5, which is an excellent result. The total number of PI error blocks (14,404) confirms the highest quality of the disc, too. The peaks of PI failures don’t exceed 3; the average PI failure rate is 2. The total of PI failures is small (771), too.

Like in the previous case, there are steps in the Beta graph after which the drive was accelerating its speed. So, the overall shape of the graph is somewhat uneven. The same can be said about the Jitter rate. The drive is constantly adjusting the laser power which immediately affects the shape of the graphs, but doesn’t influence the quality of the resulting disc.

The TA Test shows the drive’s ability to maintain necessary pit and land lengths. The adjacent sections overlap on the diagram, but not too much. The Peak Shift value isn’t as high as to affect the quality of the disc.

Thus, the ASUS SDRW-0804P-D handles DVD+R media well at both 4x and 8x speeds. Let’s see how it burns dual-layer media.

The burn operation was completed without problems – no slowdowns on the graph. Although the software identified the employed burn algorithm as CAV, the graph clearly shows that it is a classic CLV. You can also see the moments when Running OPC technology starts to work.

The quality of the first layer of the resulting disc is rather average. The average PI error rate is very close to the maximum limit. There are also rather lengthy surges of PI failures above the acceptable limit. The situation improves on the second layer, though, where the errors fit into the norm.

The Beta graph reflects the drive’s incessant adjustment of the laser power and is jagged as a result. The Jitter rate is not uniform along the disc, either. The drive doesn’t seem to have found the optimal laser power and this affected the quality of the resulting disc negatively. As for the correct lengths of pits and lands, the adjacent areas do overlap on the diagrams for both first and second layers. The Peak Shift value is high, too. It means the average length of both pits and lands differs from the reference.

Like when burning the DVD+R at 4x speed, the ASUS drive again uses Z-CLV. Yes, this is a two-step Z-CLV algorithm with a very short first step, so the whole burning operation is not greatly slowed, but it is still Z-CLV. Why could the manufacturer choose this algorithm? Maybe because the drive needs more time to choose the optimal burn strategy and to adjust the laser power appropriately.

Unfortunately, the quality of the resulting disc is worse than that of the DVD+R. Yes, the average rates of PI errors and failures are quite acceptable and even low, but the drive burns DVD+R discs better, that’s a fact. By the way, an increase in PI errors can be seen right after the drive reached 4x burn speed, so the drive’s being “cautious” doesn’t help here.

Well, the problem may be in the manufacturers’ paying less attention to optimizing burn strategies for the minimal speeds.

The Beta graph again shows that the drive is always in search of the optimal laser power. The graph isn’t straight even in the CLV area. The same goes for the Jitter rate: it changes each time the laser is recalibrated. It seems like the manufacturer left the DVD-R 4x burn strategy in the drive’s hands entirely and the device itself is trying to find a way to burn such discs better. It maintains the necessary lengths of pits and lands well, though (Jitter is minimal). The rather big Peak Shift value spoils this bright picture somewhat, yet overall the results are highly satisfactory. Let’s see what we have at a higher speed.

The SDRW-0804P-D shows its conservatism once again. Its four-step Z-CLV algorithm slows it down considerably in comparison with “desktop” devices. Yes, speed is not the main priority for a notebook drive, but I think users would want to know why their device takes much more time than other drives to burn a disc, the speed formulas being identical. Apart from the employed burn algorithm, the burn operation proper was performed without problems.

The resulting disc is very good. The rate of PI errors and failures is normal (the PI failure rate approaches the allowable maximum on the outermost tracks only). But if we compare this to the quality check of the DVD+R recorded at 8x, we will have to acknowledge a worsening of the results. So I should say it again: the SDRW-0804P-D burns write-once media of the “plus” format somewhat better than discs of the competing format.

The Beta/Jitter graphs again show that the laser power is constantly being adjusted throughout the burn session. The Beta graph stabilizes after the one third of the disc and becomes more like a horizontal line, while the Jitter rate is always changing. On the other hand, the results of the TA Test suggest that the drive maintains the required lengths of pits and lands well enough (the Jitter and Peak Shift parameters are both low).

Summarizing the results of the tests with write-once DVD media, I must acknowledge that the ASUS SDRW-0804P-D burns DVD+R and -R discs very well, but DVD+R discs it produces are somewhat better quality than DVD-R. It seems the manufacturer focused more on developing burn strategies for the +R format in the first place.

As for dual-layer DVD+R discs, the drive doesn’t burn them well. Even though the parameters of the resulting disc are within the acceptable ranges, there’s still much space left for improvement.

Rewritable Media

The drive successfully burned the disc, without any slowdowns. The quality of the disc is not, however, the best possible. The PI error rate is no higher than 50 almost on the entire disc (and this is an excellent result for a rewritable medium), there are peaks of PI errors (up to 350) and PI failures (18) at the outermost tracks. This is unsatisfactory, of course. The drive evidently cannot keep the quality acceptable as it approaches the outermost tracks of a disc.

The Beta graph shows that the drive increased the laser power at the moment right before the error rate went up. Probably it did so to compensate for the vibration that gets stronger on the outermost tracks, but the result was poor. The Jitter rate is, on the contrary, good along the entire disc. On the other hand, the TA Test results indicate that the drive cannot keep the lengths of pits and lands as they should be when writing DVD+RWs at the min speed. The adjacent areas overlap on the diagram; Jitter is high and the average length of pits and lengths is far from perfect. So, we should acknowledge some problems with DVD+RW media at the min speed. Let’s see what happens at 4x.

The drive still uses a Z-CLV algorithm for processing discs at 4x speed. This increases the overall time of the burn session. Otherwise, there are no problems with burning proper.

The average rates of PI errors and failures are low, except the outermost tracks where there are surges of errors, like we have seen at 2.4x speed. The PI errors are still within the acceptable range, while the peaks of PI failures are three times above the norm and may render the disc unreadable.

Unlike at 2x speed, the laser power is not increased on the outermost tracks. The drive boosted the power as it transitioned to 4x speed and then the Beta graph is nearly a horizontal line. The Jitter rate is more uniform along the entire disc than in the previous tests and is smaller, although not ideal: the adjacent areas overlap rather much on the diagram. The Peak Shift is small.

Thus, the quality of the resulting disc is tangibly higher at the higher burn speed.

The burn session was completed without problems. The quality of the resulting disc is high: the average PI error rate is about 8, which is especially good since we deal with a rewritable medium. Despite the high density of PI failure block, the average PI failure rate is about 2, again confirming the high quality of the disc.

The Beta graph is nearly horizontal, with minor deflections. The Jitter rate is roughly the same on the entire disc, too. The TA Test results agree as to the high quality of the disc: the Jitter value is small and Peak Shift is zero altogether. The drive maintains the required lengths of pits and lands almost ideally.

It’s not surprising anymore to see a Z-CLV algorithm at 4x burn speed. Otherwise, the drive performs writing well enough, producing a disc with a very low rate of PI errors and failures.

The Beta graph isn’t ideal, but good. Note also that the drive is reducing the laser power during the burn session, contrary to what we have seen with DVD+RW. The Jitter rate remains roughly the same throughout the entire disc. The TA Test results show a higher Jitter and a minor deflection of the average pit/land length from the etalon than at 2x speed. Yet overall the quality of the disc is high.

So, talking about rewritable DVD media, the ASUS SDRW-0804P-D again shows a predisposition to one of the competing formats. This time, however, it is the “minus” format. As for +RW, my main complaints are about the outermost tracks where there are considerable surges of errors. It is possible the manufacturer will correct this defect in firmware updates. But taking the results as a whole, I must say the drive processes rewritable DVD discs very well.

Audio Capturing

This drive hardly suits for processing audio data. First, many popular sound-processing programs, including EAC, do not support this drive. And second, the results of the Advanced DAE Test suggest that this drive is just not designed for such tasks.

The rather big offset is not compensated with reading from the auxiliary areas of the disc, so the user is unlikely to get a precise copy of an Audio CD. The maximum “on the fly” grabbing speed is limited at 4x which is another disadvantage of the reviewed device.

On the other hand, we must again make allowances for the class the drive belongs to. It is simply intended for other applications. Users who want an all-purpose optical drive are still limited with internal devices with the IDE interface.

Conclusion

It’s time to summarize our experience with the new external optical drive from ASUS.

As I already said at the beginning, portable optical drives have certain inherent drawbacks which we later saw in the tests. The SDRW-0804P-D is not to be considered as an equivalent replacement to the internal optical drive installed in your computer. Its main purpose is to give you ability to read and write optical discs wherever you are. And this model is up to its purpose with its small dimensions and low weight, high burn quality and low noise. With the above-mentioned reservations, this cutie may make an ideal companion not only for mobile but also for a desktop PC.

It is an enjoyable experience to work with this device and its minor flaws cannot obscure its obvious and numerous advantages which are listed below. But again, when evaluating this device you should make allowances for the category it belongs to. Portable optical disc drives are different than desktop optical drives and should be approached with different evaluation criteria. All the more so when the portable optical drive is also external.

ASUS SDRW-0804P-D DVD±R Burner: Small Drive with Big Capabilities