Dumping SVI (Spectravideo) disks.

All questions about how to use KryoFlux go here.
Post Reply
Icon
Posts: 11
Joined: Thu Feb 16, 2017 10:59 pm

Dumping SVI (Spectravideo) disks.

Post by Icon » Mon Jul 24, 2017 11:40 am

Hi!
I have search the forum but cant find a topic regarding SVI(Spectravideo) disks.
I have come over a lot of SVI disks both CP/M and, what I understand "regular" SVI-dos disks.
Anyone here ave any knowledge how to dump them correctly?
I have tried to dump them both as MFM and FM without any result.
Best regards
Snoddas /The Preservers

SomeGuy
Posts: 105
Joined: Wed Feb 18, 2015 8:18 pm

Re: Dumping SVI (Spectravideo) disks.

Post by SomeGuy » Mon Jul 24, 2017 2:17 pm

Do you know exactly which Spectravideo system these were from? Off hand, I see that there are several different formats: Spectravideo 318/328 - SSDD 48 tpi 5.25", Spectravideo SV-328 - DSDD 48 tpi 5.25", and it also looks like there was a 3.5" drive.

I believe these use a mixed FM/MFM track format. With the Kryoflux software, that means you will have to use two different dumping profiles, and dump to two separate unstructured image files. Of course, as always, you should create and keep a full preservation stream dump. (You can feed the preservation dump back to the KF software for further decoding and analysis later without wearing out your original disks)

Off hand I'm not sure if there is a commonly used "go-to" image format for this system, that is preferred for archiving or emulators.

Can you post a sample image file?

Icon
Posts: 11
Joined: Thu Feb 16, 2017 10:59 pm

Re: Dumping SVI (Spectravideo) disks.

Post by Icon » Mon Jul 24, 2017 8:25 pm

Thank you for quick answare! The floppys I have is all 5.25" and some 40 tracks DSDD and some 80 tracks DSDD. The 80 tracks is CP/M floppys for SVI. Wonder if they are in another "format" then the "regular" SVI floppys?
I have dumped three floppys that you can take a look at (raw files).
http://the.preservers.se/SVI%20CPM%2040track.rar
http://the.preservers.se/SVI%20CPM%2080track.rar
http://the.preservers.se/SVI%20DSDD%2040track.rar

The emulator "BlueMSX" has support for SVI floppys in different formats and what I have understood that as you have stated, they are mixed MFM and FM. So what did you mean when you say that I need two different profiles?
Thank you in advance for your help.
/Snoddas

SomeGuy
Posts: 105
Joined: Wed Feb 18, 2015 8:18 pm

Re: Dumping SVI (Spectravideo) disks.

Post by SomeGuy » Tue Jul 25, 2017 3:25 am

Ok, these disks use FM encoding on track 0 head 0 with 18 sectors of 128 bytes and an interleave of 2.
Track 0 head 1 and later all use MFM encoding with 17 sectors of 256 bytes and an interleave of 2.

Both your CP/M 40 track and SVI DSDD sample are in this format.

Your "SVI CPM 80track" image is a single sided version with 40 tracks. Not sure where you got "80 tracks" from.

Taking a quick look at that emulator, apparently it does simply use unstructured sectors images. That seems a little strange to me, as you then have to know exactly what system the image was from in order to know the sector geometry to recreate a physical disk. But obviously less trouble to implement in an emulator.

If you look at the kryoflux GUI you will see that it has different "profiles" for a number of different formats. It has one profile for general MFM decoding and another for FM decoding. Unfortunately the Kryoflux software can not auto-detect encoding type or sector size. This means you will need to configure one profile to read the FM part with 128 byte sectors, and another for the MFM part with 256 byte sectors. You can select multiple profiles read everything in one pass. (The DTC command line tool can be used to automate all of that)

That normally will create two unstructured sector files for each of the two parts. Since that emulator just wants a single unstructured file, it looks like just copying the two together should create a file that the emulator can use.

In the case of the double sided disks, the final file size should be 346,112 bytes.

If it were me, personally I would want the images in Imagedisk format as that preserves sector layout information and can be easily written on an IBM PC compatible that happens to support FM encoding.

Icon
Posts: 11
Joined: Thu Feb 16, 2017 10:59 pm

Re: Dumping SVI (Spectravideo) disks.

Post by Icon » Tue Jul 25, 2017 7:06 pm

Again, thank you for your help here...
The disk had "80track CPM version" written on a label on it, so i assume that was the case! ;-)
Regarding profiles I had thought it was what you meant, just had to me sure.
Its a huge pile of floppys so I will start woth just "flux" them to raw and then elaborate and sww what I can come up with. Your info had leed me on the right path. Sadly I dont find any "converter" for ".img" to whatever BlueMSX support.
The work goes on... :-)
Best regards,
Snoddas

Jope
Posts: 7
Joined: Thu Sep 08, 2011 5:08 pm

Re: Dumping SVI (Spectravideo) disks.

Post by Jope » Thu Aug 10, 2017 9:28 am

I think you already got the link from elsewhere, but recording it here too:

My quick svi script that has been beautified without access to a kryoflux + drive (I'm at work)

http://bitbucket.org/vjouppi/kf-svi/

Icon
Posts: 11
Joined: Thu Feb 16, 2017 10:59 pm

Re: Dumping SVI (Spectravideo) disks.

Post by Icon » Fri Aug 11, 2017 10:43 am

I was about to post your script here! :-) Thanx a million! I have now succesfully dumped all the 200 floppys thanks to your script! :-)

Post Reply