TOPIC
I have an 8x CD-ROM drive which gets 1195kB/sec (using ASTARTE CD-Copy Disc:Check_Tracks) but my PowerBook 3400c 12x barely makes 750kB/sec (on the same CD).
DISCUSSION It is possible for an external CD-ROM drive or desktop CD-ROM drive to transfer data at a faster rate than a PowerBook internal CD-ROM for several reasons. The PowerBook internal CD-ROMs are designed to work on 5 volts instead of 12 volts like the desktop drives. This means the motors take longer to spin up to speed and do not run quite as fast. The PowerBook drives are more suseptible to vibration or uneven CD-ROMs. When the drive checks the vibration level and it is too much, the drive slows to around 5.5X speed which would be equal to around 700-800k a second. Desktop CD-ROMs do not have the vibration issues because they have room for dampers and the larger mechanism which handles unbalanced media much better. Also, when the CD is reading the inner tracks (directory) it will slow down to (5.5X) since this was the only way to help reduce vibration with the 17mm CD mechanism. So this is a possible reason you may see only 700-800k/sec. When the drive is reading the outer edges it will speed up to 12X speed or around 1.8MB/sec. If the CD is not uneven the 12X CD-ROM should get around 1.8 MB/sec with burst modes of up to 10 MB/sec. Note: The PowerBook G3, which has a 20x CD-ROM drive, is affected by the same issues. |
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| Document Information | |
| Product Area: | Computers |
| Category: | PowerBook |
| Sub Category: | General Topics |
| Keywords: | kpbook |
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