Sega SF-7000 3" drive support

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Omar
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Joined: Fri Dec 31, 2010 4:17 am

Sega SF-7000 3" drive support

Post by Omar » Fri Dec 31, 2010 5:17 am

Hello and happy holidays!

I'm new to KryoFlux. I have purchased a kit yesterday based on various recommendation but otherwise haven't checked in details your software and solution yet.

We have 14 years running community called SMS Power! (http://www.smspower.org) interested in preservation of all things Sega 8-bit. Among our work, we dumped and catalogued thousands of cartridges from all over the world.

Over the years and with the people of many people I assembled 200+ disks for the SF-7000 system (Sega Super Control Station), a very obscure extension to the SC-3000 (Sega Computer 3000). The SC-3000 is a 8-bit Z80 based system with 2KB RAM and running code off cartridge. The SF-7000 adds up 64KB of RAM and provide a 3" floppy disk drive running with a FDC765 controller, which I believe is the same as CPC.

It looks like that: http://www.sc-3000.com/images/stories/a ... F-7000.jpg

Various people originally dumped a few disks using a software solution running on the SF-7000 Basic, reading sectors and transfering to a PC via the serial port. However this solution is very slow and the amount of CRC errors, etc makes it a pain to deal with. I postponed dumping until we had a better solution. I once tried to work with the people making Catweasel but it didn't go anywhere due to a lack of focus on both side and probably also lack of fund.

Finally KryoFlux came to grace us! :)
Questions!
- Can I use KryoFlux to dump those disk safely ?
- Do you guys would have any use of sample disks if there's anything to reverse engineer ?
- Do I need to source a mint 3" disk drive for best result? (and can you help with that?). I know that SF-7000 and CPC drives are interchangeable.
- Do we have to update emulator software to support new formats? (only a handful emulators support SF-7000, MESS and MEKA coming to mind, the later which I wrote)
- Can we use KryoFlux to write back to disks images that could be run on real hardware?
- Any recommendation or anything I should know?

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IFW
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Joined: Mon Nov 08, 2010 2:42 pm

Re: Sega SF-7000 3" drive support

Post by IFW » Fri Dec 31, 2010 6:01 am

Welcome and Happy New Year (soon) :)

Dumping a disk is as safe as is the drive you use.
I'd definitely recommend dumping disks that are home written etc, ie not important for testing a drive in an unknown condition.
e.g. a dirty head can cause serious damage to the disk surface.
It's also a good idea to check that the disk surface is not dirty or damp either.
If it's the same as the CPC and Spectrum+3 drives it's quite difficult to get a drive in good condition, and the belt for the spindle motor will probably need to be replaced.
I am sure our CPC and Spectrum+3 guys would chime in on these matters :)

CPC and Spectrum+3 dumping definitely work, so it should be fine - what the disks contain we'll see I guess.
Disks are not needed since you have a board already, the stream files would be just fine - we'd just read the disk content out into stream files as well.
If the content is something unsupported, then yes, reverse-engineering is required. Again, we'll see...
Check out the CPC related threads.

As for CPC and +3 yes, emulators were updated for supporting IPF, but the games on those systems can be very heavily protected - IPF was designed to hold mastering data (ie disk content and context) to the flux/encoding level so IPF files can hold everything, but if it turns out that the SF system used unprotected disks or ones with simple protections you could possibly do with just using an existing format.
Once we have a few dozen disks dumped we'll find out.

Depending on how advanced the disk controller usage is, emulators may have to be updated anyway, e.g. for Atari ST we have cycle exact FDC emulation (reading flux transitions, timings and emulating all undocumented features of even how the address mark detector modifies data which took several months to re-engineer the exact sequence etc), but CPC and Spectrum+3 uses on-the-fly device emulation that is higher level for running IPF files.
It all depends on how far those games go in taking advantage of the FDC hardware - hopefully what is needed is more along the lines of CPC emulation then Atari ST or Amiga ;)

Yes, writing is work in progress, initially for IPF files though as they definitely have authentic and unmodified content plus every information required for authentic remastering, unlike anything else.
Other formats will follow though, but not ones that need any sort of emulation e.g. emulator detects specific image/protection and emulates it, instead of using the real disk data.
I am sure we could work out something that would be useful for SF games if rewriting them is interesting.

As for everything else, right now I'd recommend reading the manual, the board and asking, really :)

Omar
Posts: 4
Joined: Fri Dec 31, 2010 4:17 am

Re: Sega SF-7000 3" drive support

Post by Omar » Fri Dec 31, 2010 7:01 am

Thanks for your detailed answer. It sounds like it could be rather hassle free here.
Few developments has been done on the SF-7000, probably more than half of it relying on the high-level Basic software and other maybe using the ROM system calls, so I have a gut feeling that very low-level emulation and contrived protection scheme support wouldn't be very necessary. By all means, unless I have some unknown gem somewhere on my disks, its not a system which hardware was really pushed.

I am correct thinking that there is only one way to read the low level stream? By which I mean that once I get low level dumps of everything, we can figure out the format and decide later how low-level the emulation can or not be? Or does a feedback loop of reverse-engineering, tweaking software code or settings, dumping again, can be required?

What's your gut feeling on what classifies as good/dangerous drives? I have a few drives that I used successfully on the system but I can't tell how good they are. Is it possible to clean a dirty head, or clean disk surfaces? I have secured some new belts a few years ago. I would buy a good drive if occasion is given.

PS: My schedule is that I'm now in Japan and won't get back to my SF-7000 stuff until a few months, so this thread will probably go idle for a while.

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IFW
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Re: Sega SF-7000 3" drive support

Post by IFW » Fri Dec 31, 2010 2:35 pm

Yes, that's the nice thing about dumping at the flux transition level - you practically record what the drive tells the host system/controller. It can't get any lower on the drive interface, so the reverse-engineering, format definition etc and transformation can happen at any later time using the recorded/dumped files.
Just like with lossy vs lossless compression: you can always create something less detailed depending on need if you have the original samples, but you could never use a high level file to recreate the exact original content.
Actually, there is one level lower possible, if you'd directly sample the drive head data input before the amplifier/filter etc logic, but chances are you'd want to do exactly what the circuit does there anyway... plus you'd need different hardware for each and every drive model, custom modified by hand to do that.

Yes, it's possible to clean a drive head and it is also possible to clean a dirty disk surface or even "transplant" a valuable disk if the coating is damaged or after cleaning the disk surface - but I wouldn't attempt to do that...
Our resident drive/disk cleaning maestros Mr Vince and Interceptor would be more useful on this topic.

I guess there is no rush after 20+ years... although 3'' disks seem to be the least reliable so far in keeping their content, at least according to the dumps we have.

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robcfg
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Joined: Mon Dec 27, 2010 9:55 pm

Re: Sega SF-7000 3" drive support

Post by robcfg » Sat Jan 01, 2011 3:45 pm

Hi,

I think you can use any 3" drive with the SF-7000 disks. If you don't want to make a special cable to attach it to the KryoFlux unit, you can always get an Amstrad FDI-1 unit, which works flawlessly.

Image

Beware that there is an almost identical disk drive, which is the DDI-1 ,that has a 5V line in the data ribbon that could damage the KryoFlux unit, and was used to power the Disc Interface for that drive.

If you want to build the cable here you can see how to do it (in spanish, but should be easy enough to understand).

If you have any doubts or questions, don't hesitate to ask.

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mr.vince
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Joined: Tue Oct 05, 2010 5:48 pm

Re: Sega SF-7000 3" drive support

Post by mr.vince » Sat Jan 01, 2011 7:21 pm

Robcfg, don't operate your KF board on the antistatic bag, it's conductive and might damage (shorten) your board.

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robcfg
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Joined: Mon Dec 27, 2010 9:55 pm

Re: Sega SF-7000 3" drive support

Post by robcfg » Sat Jan 01, 2011 10:40 pm

Woops, thanks for the tip!

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mr.vince
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Joined: Tue Oct 05, 2010 5:48 pm

Sega SF-7000 3" drive support

Post by mr.vince » Sat Jan 01, 2011 11:52 pm

Well... It's highly unlikely but... Better be safe than sorry.

Specfreak
Posts: 17
Joined: Wed Jan 12, 2011 10:18 pm

Re: Sega SF-7000 3" drive support

Post by Specfreak » Wed Jan 12, 2011 11:27 pm

@robcfg,

The FD-1 also has the extra power supplied to the floppy cable, check out fig.5
Image
http://newton.sunderland.ac.uk/~specfre ... se%203.jpg

....on my way out-of-date web page for +3/CPC disk dumping:
http://newton.sunderland.ac.uk/~specfreak/FD1/
I found this out while almost blowing up my old P75 mobo :-o.

The interface inside it, which has been useful for disk dumping over the years is also on the page:
Image
http://newton.sunderland.ac.uk/~specfre ... ce%201.jpg

Just for the sake of it a kind soul made me some 20 adaptors which over time I've sold/loaned to try and encourage people to dump disks for me.
http://newton.sunderland.ac.uk/~specfre ... PsAdaptor/

BTW, I noticed in your picture that you're using the PSU/Molex adaptor for power, does this need to be plugged in, as today when I tested my
FD-1 Unit and Kryoflux I just used the FD-1s built in power (minus of course the power supplied to the floppy cable :-o ).
I wonder what the recommendation is, or whether to use the PSU/Molex anway ?

Anyway, cool beans, gotta grab the script for Speccy/CPC and see what it yields for me. Unless it's too busy at work and I don't get around to messing with it.
I'll try and grab some shots of my Set-up at work (away from the missus you see ;-) ), with my Super-Amiga sitting next to it:
http://newton.sunderland.ac.uk/~specfre ... Amiga.html

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robcfg
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Joined: Mon Dec 27, 2010 9:55 pm

Re: Sega SF-7000 3" drive support

Post by robcfg » Thu Jan 13, 2011 7:23 pm

You don't need the use the molex cable, I simply connected it by pure inertia XD

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