Jules Richardson wrote: I keep wondering if the disk media could be "mounted" like a specimen on a slide. Then a flying head wouldn't be an issue, and multiple passes become possible. Doc

Dave McGuire wrote: No, that wouldn't be much different from the original jacket. I was thinking more like actual slides. A thick rigid base and a very thin, hard cap, with the media immobile between them. The whole assembly would turn in the reader. I don't know whether the media could actually be read through that, but if so, it would cure a world of ills. SS disks could be permanently mounted; DS you'd have to be able to remove and reverse the disk. Doc

On 21 Feb 2008 at 15:40, Jules Richardson wrote: Isn't the Bernoulli drive a non-contact system? IIRC, the media is about the same flexibility as a standard floppy disk. And 4x speed drives were used routinely in duplication equipment, so I don't know what the upper speed limit is, but 1200 RPM should be workable. Floppy recording is done at about 5876 BPI for 360K 5.25" and 17,434 BPI for 1.44MB 3.5". You can get developer in very fine (10 nm) particle size. See, for example: http://www.sigma-hc.co.jp/english/media.html I think they've been available for awhile: http://www.tristantech.com/pdf/SMM-401_v0.2.pdf Serious bucks, though. Cheers, Chuck

On 21 Feb 2008 at 21:43, dwight elvey wrote: Er, GMR? http://en.wikipedia.org/wiki/Giant_magnetoresistance not to be confused with the superlatively exciting Colossal Magnetoresistance. Cheers, Chuck (wonder what's bigger than "Colossal"?)

So I do have some news on the earlier subject. I've received the disks for UniPlus yesterday and was able to image them. I'm wondering if temperature had anything to do with it. They sat outside my house (in the box) for a few hours and were obviously cold when I read them. I disregarded the usual good idea of acclimation and immediately attempted to image them, mostly because I keep an air conditioner on at all times in my computer room (which of course in this weather acts as a fan). So if anything, the difference between the machine and the disks was less than 20F. All of the disks read just fine, with the exception of a single disk, which initially failed to read after about the 1st 10 tracks, but later, after I finished imaging the rest of them, I retried it, and that disk worked. I suspect that either the lower temperature helped, or perhaps that one disk that initially failed had some dust which was loosened and allowed to it read the second time around. I'm loathe to mess with these disks anymore as I need to return them to their owner, and don't want to expose them to any more risk. This isn't a very large test set since I didn't attempt reading them at various temperatures and with different drives/machines. Maybe I'll try just one of the disks to see if it reads at warmer temperatures, but it's an interesting hypothesis anyway. Maybe if I find a set of slightly bad non-critical disks in my collection, I can try this again with those at varying temperatures. So I'm wondering if temperature has any affect on media readability. To wildly jump to a conclusion here, would colder temperatures stiffen the media, making it easier to read? Certainly they would cause the metal in the center of the cookie to contract, but would it have the same effect on the plastic or whatever's under the magnetic coating? (NOTE: I'm not suggesting that if you have fragile unreadable media that you should try this, I'm only asking if this is a possibility. Don't risk it based on this single one-off sample! There's always the danger that the plastic does stiffen and in doing so may cause the magnetic coating to flake off?) (Of course a much simpler explanation is that the disks were originally read with a marginal drive, possibly misaligned or dirty.) There were a few other factors that I'm wondering about. The media was written by a 400K GCR floppy drive in the Lisa. These of course have a larger r/w head. The drives vary the motor speed depending on the track number - there are 4 speeds for these drives. Later versions of the Apple drives known as SuperDrives (not to be confused with the modern DVD "SuperDrives") have smaller heads in order to support HD media (which they do so only in MFM), but they still support physical reading and writing of GCR disks for DS/DD and SS/DD. The SuperDrives however do not vary the motor speed, but rather have a fixed rate spindle motor and vary the shift register read/write rate. I would theorize that the smaller r/w heads might make it harder for data recovery iff the tracks are slightly misaligned or the data is partially damaged, the smaller r/w head wouldn't see the whole width of the written track, and any damage to the area that it would see would prevent it from reading the drive, while an original 400K or even an 800K drive would see the whole width of the track, and average out the missing data with the existing data, possibly making it more readable. Any merit to this idea? Perhaps for the original subject for the floppy reader/writer board, having actual DS/DD drives as well as a DS/HD drives is more ideal? i.e. have both a 720K and a 1.44M 3.5" drive as well as both 5.25" 360K drives and 1.2M drives and switch according to whatever was used to write to the drive? In my case, I was able to read all of the disks with a SuperDrive, and a later model of a SuperDrive at that, so this didn't apply at all. (The TAM is built from notebook components, and was built later than most superdrives.)

Chuck Guzis wrote: I do keep the AC on in my computer room 24/7, although in winter, since it's so cold the condenser almost never kicks in. So I suppose it was at most 60'F. Outside was 30-something so the disks were about 40'F at most. Somehow, in this case, I no longer suppose the temperature was involved. Before sending out the disks, I re-read them again, and every single one read just fine. I expect it was a case of the owner's drive being dirty/misaligned. Wow, I remember Elephant. :-) They were one of the first disks I bought, something insane like $2 @ for 5.25" SS/DS... they were pretty awful when new, I'm not sure I'd put'em in a drive after all these years.