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Re: SCP disk images !

Posted: Thu Jan 05, 2017 9:46 am
by flyers80
Thanks for the information
I did not think there were emulators PC / dos with support of protected disk images.
Now I'll try to do testing.


coolhaken wrote:Every dump of the other one doesn't contain the protection tracks, so doesn't work.


It's a shame because it was a rare version with high-resolution EGA support instead of the Tandy mode
you can bypass the protection system with a crack?

Re: SCP disk images !

Posted: Thu Jan 05, 2017 12:15 pm
by coolhaken
flyers80 wrote:It's a shame because it was a rare version with high-resolution EGA support instead of the Tandy mode
you can bypass the protection system with a crack?


Sorry, I can't crack it.

Re: SCP disk images !

Posted: Thu Jan 05, 2017 8:37 pm
by flyers80
hi all
Uploaded to "Incoming SCP/Amiga by flyers80" another 16 Amiga games

Re: SCP disk images !

Posted: Sun Jul 09, 2017 6:51 pm
by ijor
JimDrew wrote:Jitter from an index pulse sensor is expected, but it's only measured in tens of nanoseconds. I use standard off the shelf hall sensors in critical flight control system applications for measuring positions with incredible accuracy. I am sure every type of drive is different for accuracy, but I have not seen any accuracy issues that are remotely close to a bitcell duration.


I finally had a chance to perform some authoritative measurements. I hooked a Logic Analyzer to a floppy drive and captured the index and read signals while reading the track. It was taken at the floppy cable. There is no FDC, controller, FPGA, CPU or whatever involved. This is what the drive outputs. I recorded a special track handcrafted to avoid any write splice issues and to make easy to identify the flux transitions.

These are the captures on two consecutive revolutions:
FlpyIndexJitter-1.jpg

FlpyIndexJitter-2.jpg


As you can see, the distance between the index edge and the short flux transition differ in more than 5 microseconds between both revolutions. And the captures clearly show that in one case the first transition after the index is the short one, in the other is a long one.

This is from a high quality (TEAC) 5.25" drive. If I can I'll measure with a 3.25" drive, that I expect to have a smaller index jitter.

Re: SCP disk images !

Posted: Sun Jul 09, 2017 6:58 pm
by JimDrew
Look at the end of the track (to the next index pulse). You will likely see that the track is just shifted forwards/backwards in reference to the index mark. The bitcell times are still all the same (when taking account for drive speed). Some drives apparently do this, and definitely the ones I have tested don't. This a hall sensor that triggers on a magnet passing. It's not like an optical sensor where the index hole can be slightly off depending on how the disk centers.

Re: SCP disk images !

Posted: Sun Jul 09, 2017 9:13 pm
by ijor
JimDrew wrote:This a hall sensor that triggers on a magnet passing. It's not like an optical sensor where the index hole can be slightly off depending on how the disk centers.


It is an optical sensor. As I noted, it's a 5.25' drive, not a 3.5" one.

Re: SCP disk images !

Posted: Wed Jul 12, 2017 9:11 pm
by JimDrew
Ah... ok, that makes sense then. Yeah, the disk itself can actually "wobble" on the hub as it rotates.

Re: SCP disk images !

Posted: Fri Jul 14, 2017 7:52 am
by ijor
Well, now I measured with a 3.5" drive. Hall sensor or not, the jitter is not much better than the 5.25" drive I measured before. Index edge jitter is still in the order of microseconds. This is not a track shift, I captured multiple consecutive revolutions, and the index pulse relation to the flux transitions changes (slightly) across revolutions.

I used a different logic analyzer that can capture in segmented mode. The beginning of each revolution, just around the active (falling) edge of the index is captured:

Segmented-Annotated.png


The image shows two segments, numbered 6 and 7. They correspond to two consecutive revolutions. Each segment starts just before the index edge. The top waveform signal is the flux transitions on the Read signal. The bottom one is the Index signal. The green dotted bars (one on each revolution) mark a couple of shorter transitions that I recorded to measure the position. If there wouldn't be any Index jitter at all, the distance from the index edge to the bar should be always the same.

Count the transitions between the falling edge of the index and the green dotted bar. The first revolution has three transitions. The second one has four. The fourth transitions before the green bar is marked with a blue oval. In the first revolution is before the index edge, but in the second one is after the edge. This simply means that this particular transitions is omitted if the first revolution is captured edge to edge.

Conclusion:

As I was saying, capturing a single revolution might not get the complete track, one (or more) transitions might be missing. If the track has, so called, data under the index, then simply some data might be missing.

Obviously this doesn't happen always. Not every track has data under the index. In some platforms is very common (typically 8-bit ones), in others not so much. And even then, the jitter is not always that bad that a transition is missed in a revolution as shown in the posted image.

Re: SCP disk images !

Posted: Mon Jul 17, 2017 10:40 pm
by JimDrew
It's always been the case that if there is data under the index pulse that you have to capture 2 revolutions.

What 3.5" drive did you test? I don't see this with Samsung 321 and a few others that I have tested.

Re: SCP disk images !

Posted: Tue Jul 18, 2017 12:50 am
by ijor
JimDrew wrote:What 3.5" drive did you test? I don't see this with Samsung 321 and a few others that I have tested.


TEAC combo (3.5 and 5.25). Can't check the exact model number right now. Note that they are really two piggybacked independent drives. But fitting in a single internal bay, the combo is very convenient. Tested the 3.5 drive only on the combo. The previous capture was on a different 5.25, DD (not HD) drive.

Re: SCP disk images !

Posted: Tue Jul 18, 2017 3:15 am
by Stefan jL
I added an SCP image of Zone Warrior at Atarimania... please check it out :) It claims to have no on-disk copy protection (only password from manual protection).
http://www.atarimania.com/game-atari-st-zone-warrior_10936.html

Re: SCP disk images !

Posted: Sun Jul 23, 2017 3:04 pm
by Stefan jL
That Zone Warrior dump has been confirmed good.
Here are some more SCP dumps, i made som quick testing in Steem with all of them and they worked.
milestones_softgold.7z - This is the Milestone compilation that contains: Spherical (version 2), Hard'n Heavy, Circus Attractions and Grand Monster Slam.

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Re: SCP disk images !

Posted: Sun Jul 23, 2017 4:19 pm
by Maartau
:D Thanks a lot :D

Re: SCP disk images !

Posted: Sat Jul 29, 2017 4:38 pm
by Stefan jL
The Data East release of Robocop... sorry i only have the disks.
Seems to work fine in Steem SSE.

http://arcade.ym2149.com/files/scpro/working/robocop_dataeast_atarist.7z

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Re: SCP disk images !

Posted: Sat Jul 29, 2017 5:36 pm
by Stefan jL
And here is Targhan, the disks are marked "march" and i don't know if there was any later Targhan releases that was not budget or part of compilations?
Disk 2 has my savegame... sorry :)
The SCP's did not work in Steem SSE but i wrote back to ST disks and played on my ST and they worked fine there.

http://arcade.ym2149.com/files/scpro/working/targhan_atarist.7z

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Re: SCP disk images !

Posted: Sun Jul 30, 2017 11:55 pm
by Maartau
Maartau wrote: :D Thanks a lot :D


:cheers: Thanks a lot again [smilie=greencolorz4_pdt_01.gif] :cheers: