A comparison test can be performed knowing all driver characteristics. For instance the track to track delay, physical dimension and rotating speed. You should use the same USB/IDE converter for both drivers . So, I'll test first the drivers on the IDE and only after a full characterisation I'll move those on external USB units. On 4/9/07, Dr Skip wrote: > I just finished some informal testing of several jump drives, and it > raised some questions. Perhaps someone here can explain this... > > I tested 2 drives on opposite ends of the advertised speed spectrum - > one said 30MB/s read, 20 MB/s write (assuming the PC can do that) and > was expensive, and the other was a 2 GB unit store brand for $15. No > speed rating and the absolute cheapest I could find. Available by the > handful in a barrel! Both were mounted in the same port on the same PC, > with write caching turned off. > > With a read/seek/write test utility, they both showed 8.5MB/s writes for > 5MB worth of data. This may be a limitation of the speed of the host PC, > but not bad. > > An extended, 2GB write, slowed to 1MB/s on the first drive near the end, > while the cheap one dropped to 200kB/s toward the end. The fast one took > about 15-20 minutes to fill, the second took almost 2 hours. The first > is reasonable to use real time, the second isn't. > > Considering there is no physical seek time, what would cause the speeds > to drop so much over the full transfer? Why can't the speed be maintained? > > BTW, in comparison with a real hard drive, the port itself doesn't seem > to slow down and the real drive maintains transfer rate, so that should > rule out any PC buffering problem, at least to this big of a degree. > > Any ideas? > > -Skip > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist