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mankeli
Registered: Oct 2010
Posts: 146 |
Spindle and Sparkle demos not launching
Can someone explain why demos using Sparkle or Spindle loaders can't be run from 1541U by selecting the launch file and using "mount & run"?
You got to use "Run Disk" for the whole image. 99.9999% of the C64 demos can be launched with mount & run, and somehow this only seems affect those aforementioned loaders. |
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Martin Piper
Registered: Nov 2007
Posts: 726 |
Quote: Quoting SpartaPlease correct me if I’m mistaken but it seems to me that this is only a problem if you don’t know which track you are on before the first 0.5 track step is taken by the loader. Well seems to me that generally you don't know which track you're on right after a reset/powercycle. =)
And until the disk spins, a GCR sync mark is found, the GCR header is read, decoded, and the track and sector bytes are discovered. :) |
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Sparta
Registered: Feb 2017
Posts: 49 |
Quoting KrillWell seems to me that generally you don't know which track you're on right after a reset/powercycle. =)
Can’t be too far from the one we were on before power cycling. ;p
Anyway, what I mean is that in the case of Sparkle (and Spindle too), the installer loads from track 18. Once the BAM is read after drive reset (via the above mentioned JSR $d00e in the M-E bootstrap code), I know I am still/back on track 18 and I can set the stepper bits accordingly. |
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chatGPZ
Registered: Dec 2001
Posts: 11390 |
Except when some kind of DMA loading for the first file was involved (Like 1541U or TC64 does) - which is what this thread is all about :) |
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Sparta
Registered: Feb 2017
Posts: 49 |
That’s what the read BAM call will remedy:
1. By some means (LOAD, DMA), Sparkle’s installer gets loaded to the c64
2. Drive reset (in case of real HW)
3. RUN
4. M-E bootstrap code gets uploaded and executed in drive’s buffer
5. Bootstrap reads BAM
6. I am on track 18 |
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Sparta
Registered: Feb 2017
Posts: 49 |
Tested so far on U, U2, and U2+, 1541-II, and Oceanic. |
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tlr
Registered: Sep 2003
Posts: 1791 |
Quote: Quoting KrillWell seems to me that generally you don't know which track you're on right after a reset/powercycle. =)
Can’t be too far from the one we were on before power cycling. ;p
Anyway, what I mean is that in the case of Sparkle (and Spindle too), the installer loads from track 18. Once the BAM is read after drive reset (via the above mentioned JSR $d00e in the M-E bootstrap code), I know I am still/back on track 18 and I can set the stepper bits accordingly.
The thing I found is that if anyone changes the step bits skipping the half track step, then the stepper motor may end up in an "invalid state", I guess mechanically. A subsequent normal step after that may not end up on the track you expect. I guess this is one of the reasons for the DOS implementation of "the dance".
This is what I've been using to fix that in my init code:; handle if we are positioned on a half track
lda $1c00
lsr
bcc wce_skp1
jsr head_in
wce_skp1:
; step in (higher track), then out (lower track) to settle head
; This is because some drive mechanisms will feel bad when going
; directly from step 10 -> step 00 (i.e track 18 -> reset routine)
jsr head_in
jsr head_out |
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Krill
Registered: Apr 2002
Posts: 2981 |
Quoting tlrThe thing I found is that if anyone changes the step bits skipping the half track step, then the stepper motor may end up in an "invalid state", I guess mechanically. A subsequent normal step after that may not end up on the track you expect. I guess this is one of the reasons for the DOS implementation of "the dance". Precisely. :)
Here's a hypothetical but quite realistic scenario:
1. File is loaded from directory track T18.
2. Stepper bits are at %10.
3. Drive is reset.
4. Stepper bits are initialised to %00, head remains on T18. Invalid state.
5. File is run.
6. DOS init reads BAM without errors, stepper bits and head position unchanged.
7. Loader steps to another track.
8. Head does not land on the expected destination track. |
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Sparta
Registered: Feb 2017
Posts: 49 |
Quoting tlr; This is because some drive mechanisms will feel bad when going
; directly from step 10 -> step 00 (i.e track 18 -> reset routine)
What does “feel bad” mean? What happens to the drive mechanism when the DOS reset routine does a %10 -> %00 on track 18? |
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tlr
Registered: Sep 2003
Posts: 1791 |
Quote: Quoting tlr; This is because some drive mechanisms will feel bad when going
; directly from step 10 -> step 00 (i.e track 18 -> reset routine)
What does “feel bad” mean? What happens to the drive mechanism when the DOS reset routine does a %10 -> %00 on track 18?
feel bad = to be in an undefined state
See here: https://en.wikipedia.org/wiki/Stepper_motor#/media/File:Stepper..
e.g, if you are physically in state #1 and directly change the magnets to go to state #3 you might move partially, in the wrong direction, or not at all in some cases.
This will correct itself by stepping a few times, but then everything might end up one track off. This then needs to be detected by interpreting the track field in the sector header. |
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chatGPZ
Registered: Dec 2001
Posts: 11390 |
Quote:e.g, if you are physically in state #1 and directly change the magnets to go to state #3 you might move partially, in the wrong direction, or not at all in some cases.
BTW - VICE (and i believe also 1541U) will always step "up" one half track in that situation, as this seems to be what the odd loader (i forgot the name of that demo) expects |
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