Delta transition time overflow....

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Convergent MightyFrame

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Dec 13, 2020, 11:52:48 PM12/13/20
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All,

I'm getting a lot of these, pretty much on every single cylinder

Delta transition time overflow, raw transitions will not accuractly represent cyl X

Is there more documentation on what exactly this means, that I have yet to find?

I'm working with a MicroScience HH-1050

Here's the analyze results, if this helps, which also has some confusing things in it:

root@beaglebone:~/mfm# ./mfm_read -a
Board revision C detected
Found drive at select 1
Drive RPM 3601.3
Delta transition time overflow, raw transitions will not accuractly represent cyl 2 head 1
Delta transition time overflow, raw transitions will not accuractly represent cyl 2 head 1
No more peaks in histogram
No more peaks in histogram
Primary transition period 0 ns, should be around 200
Delta transition time overflow, raw transitions will not accuractly represent cyl 2 head 1
Delta transition time overflow, raw transitions will not accuractly represent cyl 2 head 1
No more peaks in histogram
No more peaks in histogram
Primary transition period 0 ns, should be around 200
Retrying on cylinder 0 head 1
No more peaks in histogram
No more peaks in histogram
Primary transition period 0 ns, should be around 200
Unable to determine drive format

Thank you,
AJ


David Gesswein

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Dec 14, 2020, 7:54:56 AM12/14/20
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No more documentation other than reading the code. The time between
transitions is stored in a fixed bit width integer and it overflowed.
Proper MFM data has a maximum time between transistions such that this
should never happen. I've seen it when the disk is bad.

This looks suspiciously like its not getting transistions from the drive.

> Primary transition period 0 ns, should be around 200

If you make this a one in analyze.c and rebuild it will dump out a histogram of
transitions times.

#define GENERATE_HISTOGRAM 0

I good disk looks similar to this. You should have near zero counts
between the peaks. If you get all zeros then the board isn't seeing any
transitions on the 20 pin cable data lines. You can check each head with
--ana=#,# where the first is cylinder and the second head.


0, 0
1, 0
2, 0
3, 0
4, 0
5, 0
6, 0
7, 0
8, 0
9, 0
10, 0
11, 0
12, 0
13, 0
14, 1
15, 0
16, 0
17, 3
18, 1
19, 3
20, 3
21, 0
22, 3
23, 1
24, 2
25, 6
26, 5
27, 2
28, 4
29, 1
30, 1
31, 12
32, 5
33, 7
34, 7
35, 8
36, 5
37, 13
38, 213
39, 15111
40, 28475
41, 28972
42, 4383
43, 45
44, 2
45, 3
46, 2
47, 1
48, 1
49, 3
50, 0
51, 0
52, 1
53, 1
54, 3
55, 2
56, 0
57, 1
58, 4
59, 239
60, 1037
61, 1243
62, 508
63, 26
64, 0
65, 0
66, 0
67, 1
68, 0
69, 2
70, 0
71, 3
72, 3
73, 1
74, 0
75, 2
76, 0
77, 0
78, 9
79, 127
80, 279
81, 275
82, 84
83, 4
84, 1
85, 0
86, 0
87, 0
88, 1
89, 0
90, 0
91, 0
92, 0
93, 0
94, 0
95, 0
96, 0
97, 0
98, 0
99, 1
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Convergent MightyFrame

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Dec 14, 2020, 2:43:13 PM12/14/20
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David, what an excellent diagnostic tool!  The level of specificity that it provides is so far advanced.  I'm going to put in the time to learn how to use this, and I thank you for this explanation.  And the tools!

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