Canon P-150 scanning timings

The second power cable doesn't seem to be all that effective in boosting the speed of the scanner.

Using a custom SANE frontend, the timings for scanning 3 duplex A4 pages with B&W and 600DPI settings:

0: TIMING 17555283 usecs

1: TIMING 25179 usecs

2: TIMING 14859625 usecs

3: TIMING 24944 usecs

4: TIMING 15765811 usecs

5: TIMING 8385 usecs

With the second USB cable connected:

0: TIMING 14738761 usecs

1: TIMING 21129 usecs

2: TIMING 13816726 usecs

3: TIMING 17589 usecs

4: TIMING 13548819 usecs

5: TIMING 25447 usecs

The timings vary quite a bit (plus minus one second), I'm suspecting the backend does some silly synchronization dance with the scanner, but using the second cable causes the scanner to scan marginally faster (it seems that the scanner doesn't pause as often with the second cable).

I should also mention that there seems to be some stability issue with the second cable (the scanner jams internally and the backend returns Error during device I/O at sane_start()).

Also, while developing the frontend, it becomes clear that the backend/scanner combination has some issues when problems appear. It seems that the backend is unable to reset the scanner at all and one must resort to closing the scanner case physically (which power offs the scanner) and opening it again. Luckily the feeding mechanism is pretty simple to clear from jams (the scanner doesn't autofeed the page if it starts in jammed position).