Found one issue

Well, within an hour or so of getting my new LogicPort logic analyzer hooked up, I’m at least noticing some symptoms that I haven’t seen before.

The drive is putting out(or the logic analyzer and my sx is seeing) very short time between pulses. Like 2.9us, 1.7us, 2.75us, and then gets back on track. Since my SX is detecting these edges, it’s writing a “1” for each of them. This is how I end up with double 1’s.

Now the next question is, is the drive really putting out pulses that are too close together? Or is this noise?

Odd enough, i tried a disk other than my test disk and I’m not finding any weird pulses.  Maybe I’ll try another track on the same disk to see.


Amateur Electronics Design Engineer and Hacker


  • Well. I don’t think its noise on the line or anything. The pulse widths of the “bad” pulses are the same as the good pulses. I’d expect glitches to be much smaller.

    I tried a bunch of tracks on the good disk, and I don’t see those bad out-of-time pulses. Weird enough, the original test disk can be read fine in the actual amiga.

  • Could some chaotic data be read from track gap areas?

    It is impossible to write the whole track so that the last bit of the last byte was accurately placed next to the first bit of the first byte. There always will be either unerased gap (if written data is less then physical track itself), or some partly corrupted data previously written on the track. So you probably can pick that data, can’t you?

  • Yes, I’ve never really considered this, but you are right.

    This still doesn’t explain, however, the fact that a lot of the sectors on that track are unreadable. The “double 1’s” that I was seeing were somewhat even spread throughout the disk, including the middle of the track.

    If this was just track gap garbage, I would expect to see it only once, and the problem bits all located next to each other. But that’s not the case, I’ve seen it everywhere.

    I’m beginning to think that the disk has somehow gotten corrupted, although the fact that the amiga can read raises doubts.

    At this point, I’m able to read multiple real disks OK. I think I’m going to format my test disk, re-write the disk, and then try to read the test disk again.