Date: Wed, 4 Apr 2012 23:29:17 +0200 From: cb at kryoflux.com To: cctalk at classiccmp.org Subject: Re: KryoFlux and Commodore Disks Well, about 80% of the games sold for the C64 were in fact written on industrial grade PC drives with Trace machines. Many titles use 80 track mechanics and heads. It in fact works when the drive is well aligned and you make sure the disk is empty, e.g. degaussed, before you do this, otherwise you would risk keeping garbage for disks that were previously formatted in a 40 track drive with wider heads. All games that do stepping tricks with so called fat tracks or half tracks can't be written with 40 track drives at all. You are totally wrong. The drive will happily read the disk, but you need a controller that can make use of GRC coding and the special encoding tricks used by copy protections. As the 1541 is a separate computer, there is much freedom here. Really? Afaik the 80 track drives with 40 track wide heads were custom made for Commodore and don't have a Shugart connector. Indeed. These will cause trouble when read with a 1541 for various reasons. Some protections work by using the index while recording (which the 1541 does not have...), later read a specific track and then step ahead to find some special data when reading a few tracks later. You can't write such protections with a standard 1541 as it lacks the index to aling your data to. Other protections vary bit cell density, which is ok for reading, but can't be written with an unmodified 1541, some make tracks so long and write them in one pass, so you need more ram in a 1541 and some will even trick the sync detection which is not very reliable in the 1541. What makes things worse is that the format used for storing such data, g64, is very badly implemented in most of the emulators out there. To our knowledge all emulators are working with a fixed track size of 7928 bytes per track, which will give trouble for e.g. V-MAX! style disk, at least everything before V3. We are working with Pete Rittwage (author of Nibtools) to find out if we can help enhance e.g. Vice to support properly imaged disks that have demanding protections. Currently some g64s need tampering with, some even need cracking the game, because the format can't properly store the protection (see e.g. Pirates! for fun invloved). See: http://c64preservation.com/dp.php?pg=bangui6 If anyone wants to take a look... we do have V-MAX disk images of Defender Of The Crown that are definitely beyond what emulators will accept at the moment. Let me know... I would agree, at least if writing is important to the person using it. KryoFlux currently does not write g64 files, so it's for reading only (at the moment). We do have a preliminary STREAM to g64 converter, which spits out files that are correct in regard to what's on the disk (leaving out e.g. varying density in a track, which can't be stored by the file format itself), but fail in emulators, because, as written above, all of them work with a fixed track size and so forth. Some protections will fail if the track size is wrong. If you are going for an estimated 85% of things out there, can live with losing index information, don't fear messing with images, having e.g. three to four separate g64s for one game for different emulators, want to start tweaking the drive to alter rotation speed (therefore creating e.g. longer tracks at the cost of slightly wrong recording coercivity), and need a cheap solution, ZoomFloppy with a 1541 and Nibtools will work ok. I also have one for testing, it's very well executed and Jim Brain delivers quality. If you want to go beyond, KryoFlux might come handy. E.g. a 1541 will never show you recording tricks like varied bitcell width, "killer tracks" full of syncs etc. But it's work in progress, and won't be fully ready tomorrow. Modifying a drive to make it read flippy disks in one pass, like at the recording stage, is a pain. Just for the record. Enjoy. Chris