Gee! I didn't mean to suggest there was any inadequacy in what you've done here, Tim. It just rang a bell with respect to the archival discussion that went on for some weeks a couple of months back, and that suggests thee were numerous people interested enough to follow it. I have a revised sampler that will work in both directions in rework down in my basement, and I've determined it needs more memry, but there isn't much space on that rather small board. Fact is, I need to DRAM to make it fit physically, without rearranging components. Nobody else has to use them. It's just a FREE solution for me and perhaps others. Please see my embedded remarks below. Dick ----- Original Message ----- From: <CLASSICCMP(a)trailing-edge.com> To: <classiccmp(a)classiccmp.org> Sent: Tuesday, July 04, 2000 11:11 AM Subject: Re: Tim's own version of the Catweasel/Compaticard/whatever I've used the same comment myself, Tim, but what I meant by this remark is that, since most of the popular FDC's commonly used to read/write floppies are not to easy to find/implement these days, a single person programming an FDC code set into a programmable single-chipper with enough drive at the pins to dispense with the need for external buffers would be an easy and general solution to the problem of how to build an interface. I didn't intend this to be mixed up with the sampling arrangement, which could, conceivably, work in parallel with ANY FDC, but would, of course, be best with a FDC that could read/write the format in question so that it would provide assurance that a given sample of the bitstream from the FDD was readable. is to method - he/she I was not aware that any form of encryption was involved, though the sampler would, indeed grab the data as-is, and allow its external processing off line, and subsequent regeneration of the by-then-massaged file. I did suggest a completely public approach. The entire core process is achievable with a few common, standard-logic (and therefore already obsolete) IC's and an oscillator at 32x the fastest data rate one will attempt to sample. AFAIK, that would be 16 MHz, BTW. The assumption is that the device will be used with a PC that has EPP parallel port capability as nealy all PC's made after '93 have. The FDC keeps track of the heads and operates the drive mechanism, and the sampler grabs the entire track where the heads sit at that moment by tapping onto the data path, albeit in parallel by means of OC drivers. computer original on make nominal You've clearly missed my point, Tim. The PLL of which I wrote is the one on the system that will attempt to read the regenerated diskette, produced by sampling to a data file at another place and time, subsequently reduced in size, and then re-"inflated" at a resolution compatible with the appropriate write precompensation, since that MUST be used in the regeneration process. The sampler doesn't need a PLL due to the high sample rate. The FDC that later reads the regenerated file will be presented with a diskette, the transitions on which are written with the approriate write precompensation. This will mean the PLL only has to sync once per track, since all the data on a given track is coherently timed, transition-by-transition. So long as the diskette is not subsequently written, the data will always be coherent, thereby requiring no resynchronization. THIS WOULD BE BETTER THAN A BRAND NEW DISKETTE, since it wojuld be clock-coherent. This would only be of benefit to the system attempting to read the regenerated diskette. One additional advantage would be that it would allow anyone, ostensibly with any system at all capable of handling the target drive, and even some that can't, to write a diskette in any sufficiently well-understood modulation (FM, MFM, GCR, RLL, ERLL, etc) and format that's desired without having a capable FDC. A PDP-8, then, could generate a diskette readable by an APPLE-][ even though it hasn't got an Apple controller. Moreover, a PC could write hard-sectored 8" diskettes using an external 8" drive and the sampler, if properly implemented. at took unused. can aren't Modern (or fairly modern) DRAMs are quite simple, and I was thinking in terms of circuit size and cost, counting on the likelihood that most of the participants in this discussion have an old '386/486 or even a video card with 256kx4 drams on board, and therefore availablel for scavenging. 256K bytes are necessary to oversample at 32x, and thats the rate required for write precomp. Hard-sectored MFM diskettes are probably rare, but 8" diskettes in ERLL with hard sectoring would be closer to 250K. If all you do is read, you can do things with much less hardware, and much less software as well. I made no assertion that what I proposed was BETTER than anything at all. 4x oversampling is adequate for reading. That's what you set out to do. However, In the context of the prior discussion regarding archiving of boot diskettes or whatever other diskettes, a device capable of writing physically incompatible diskettes was called for. It's that target I was addressing. The reason I mentioned the SX is that it's capable of functioning as a combined HDC/FDC and possibly addressing more different formats than any of the chips I've used, largely since that's limited only by the capacity of its program store and the imagination of the author of its firmware. That came up only because I've seen more than one plaintive cry that the FDC that someone wanted either wasn't available any more, or that the one they had couldn't do one thing or another. It's a relevant concept from the standpoint that at, say 96 MHz, the SX could present an entirely self-contained solution to both these problems in addition to which it could also handle the sampling. It's possible, but not until the code is written. That, Sir, would be the ideal solution, in my opinion, since everybody could then hook up this single device in whatever way is deemed appropriate for their application, and I like the EPP myself, to handle "foreign" disk formats in any way that's desired. It would take lots of future projects off the "back burner" and let them be realized.