----- Original Message ----- From: "jamesd" <jdickens(a)ameritech.net> To: <cctalk(a)classiccmp.org> Sent: Monday, June 09, 2003 9:20 PM Subject: need 720k 3 1/2" disks with me 2 has and Have you tried using a HD floppy and putting tape over BOTH sides of the hole that marks the disk as HD? I should think that you could then format the floppy as a 720 easily. I haven't tried this myself, but "Logic is the art of going wrong - with confidence". I write enable factory-made read-only 1.44 floppies in this manner, and I use ordinary frosted "scotch" tape with great success. Stuart Johnson

Strangly, every 3.5" drive I've worked on (and I've taken quite a few apart for repairs) have mechanical sensors. Either switches, or mechanincal 'flags' that work with slottted opto-switches. In the latter case, of coursem the light beam goes nowhere near the hole. I don't doubt that drives using optical sensors exist, but I can't think of one at the moment. Yes. The old Sony drives (used in the HP9121, to tie in another thread) have the disk-inserted sensor (which is a flag + slotted optoswitch in this unit) in exactly the same position as the HD hole. These drives will not recognise that an unmodified HD disk has been inserted. -tony

On Mon, 9 Jun 2003, Stuart Johnson wrote: It sucks. We must all do whatever it takes to turn Bill Gates into a millionaire. But,... I HAVE DONE IT. Since I didn't have my copy of the "resource Kit", I didn't know that it wasn't possible (The Wiley E. Coyote principle of software development) If I were to have known that it wasn't possible, then it would have been a lot more difficult. XP dropped support of formatting 720K from the desktop, and from the command line they dropped /F:720, and dropped /F:2. But they did NOT eliminate: FORMAT A: /T:80 /N:9 Note: I did it with a recent model Compaq; it is entirely possible that the BIOS in some machines may pose other, additional problems. And in future service packs, they make fix the "error" of having left in the /T and /N. Hmmmm. Is SETVER still present in XP? If so, then it would be possible to use an older FORMAT without even having to patch it. -- Grumpy Ol' Fred cisin(a)xenosoft.com

Fred Cisin (XenoSoft) wrote: Darn you, Fred! Now I'll have to dig out that "advance" copy of Win2003 they sent me and install it on something, just to see. I had noticed that the /F:720 option was gone, but I have a DOS box that's on a lot more than the Windows box, so I never pursued it. :) Doc

On Mon, 9 Jun 2003, jamesd wrote: No, a "DSDD" can't read a DSHD because it is recorded at a higher density. WHICH IS NOT THE DIRECTION THAT WE HAVE BEEN TALKING ABOUT! The message that you just replied to was addressing the issue of whether the 720K diskette could be formatted in an ordinary PC (specifically XP). EVERY DSHD drive can read "DSDD" diskettes, so long as the disk controller supports the lower (250K) data transfer rate, and the correct software is present. That includes every disk controller that you have ever seen, although Tony and a few others may have some that were originally designed for 8" that do not support the lower rates. NO manufacturer of a 3.5" HD drive has ever made an HD drive that couldn't ALSO handle the lower density. Yes, the media is different. The differences are: different chemical coating to produce a slightly higher coercivity, and an extra hole in the diskette to tell drives which diskette it is. Those are the ONLY differences. NOTE: not all drives include the sensor to notice the disk differences. THEREFORE: as stated previously, the ability to FORMAT 720K in a 1.4M is ONLY an issue of whether the SOFTWARE supports it, and if the harware is "normal".

On Mon, 9 Jun 2003, jamesd wrote: It is not VERY different. YES, it WILL work. It will produce a somewhat unreliable, but working disk. (600 v 750 oersted) The media is different by less than 25% in coercivity. That is close enough that people who are not serious about reliability will claim that it works "just fine". In other words, in an emergency, you are likely to "get away with it". But use the correct diskette if there is any way to do so. In order to play with, or check out, the machine until you get some of the correct diskettes, you CAN play with HD diskettes. Just don't use them for any data that you aren't willing to lose. But your question also prompted discussion of HOW to "make do" with the wrong diskette (tape, etc.) and the issue that XP doesn't make it easy to format 720K (even with the right diskettes). If you are still having problems finding real 720K's let me know; I can certainly dig up a handful. But I intend to hang onto the early shutterless and manual shutter ones.

A _really_ obscure example, relating to 3.5" disks... The original 3.5" drives rotated at 600rpm, and therefore transfered data twice as fast as the corresponding PC drives, which rotate at 300 rpm. Now by an amazing coincidence, this data rate is the same as the HD data rate for a PC drive. So a controller for the original 3.5" drive should be able to handle a PC HD drive (same data rate) with the correct programming (it would be able to fit more sectors on a track than it could with the double-speed DD drive, and would have to not moan because of the longer wait for an index pulse). But this controller couldn't handle a DD disk in a normal PC drive... -tony

That seems a fair conclusion ... although I've been running XP on a machine with a 5.25" drive in it and didn't notice until right now :-) I have other machines with 5.25" drives so I suppose it's no great loss for me. Annoying though. Antonio -- --------------- Antonio Carlini arcarlini(a)iee.org

[DD 3.5" disks] Didn't we go through this last week? The coercivity of the media is different between DD and HD disks (not very different in the case of 3.5" ones, but it's still different). I would think that in the case of 3.5" disks, you could format an HD disk as a DD one, but it will _not_ be reliable. It's the sort of thing you might have to do if DD disks become unobtainable (and then I might consider modifying the DD drive to increase the write current a bit), but while you can still easily get the right media, please use it... -tony