durham@cme.nbs.gov (James H. Durham) (08/21/89)
I have read a lot recently about punching/melting a hole in your average 720K disk, then using it as a 1.44 meg disk. Now I have TONS of cheap bulk disks (DS/DD) anc converting them over would save me a LOT of money. How reliable will these converted disks be... and, besides cosmetically, what are the differences between 1.44 and 720K disks? Thanks in advance!!
sac90286@uxa.cso.uiuc.edu (Kubla Khan) (08/21/89)
In article <1516@aws.cme.nbs.gov> durham@cme.nbs.gov (James H. Durham) writes: >I have read a lot recently about punching/melting a hole in your average >720K disk, then using it as a 1.44 meg disk. I confess, it was my fault. :-) >Now I have TONS of cheap bulk >disks (DS/DD) anc converting them over would save me a LOT of money. How >reliable will these converted disks be... I haven't had a whole lot of experience using them so far (having just bought my 1.44Mb drive), but of the few disks I have punched out, about 50% have no bad sectors (at least none show up when formatted with VERIFY ON) and the rest have had around 1 Mb of usable space. How these disks will behave in the long run remains to be seen. I personally wouldn't trust anything important on them... >and, besides cosmetically, what >are the differences between 1.44 and 720K disks? I don't know for sure, but were I to hazard a guess, I'd say the 720s were 1.44s that flunked the factory test procedures. If you're worried about reliability, perhaps you should purchase the Biological Engineering disk puncher (the one designed by the CrackPot Engineer). If you buy their $40 puncher, and ever come across a disk that refuses to format, just send it to them and they promise to replace it with a genuine 1.44Mb diskette with no questions asked. Of course, this is based on the premise that the company won't go broke replacing too many diskettes... :-) Scott Coleman kubla@uiuc.edu
bill@bilver.UUCP (Bill Vermillion) (08/22/89)
In article <1811@garcon.cso.uiuc.edu> kubla@uiuc.edu (Kubla Khan) writes: >In article <1516@aws.cme.nbs.gov> durham@cme.nbs.gov (James H. Durham) writes: >>and, besides cosmetically, what >>are the differences between 1.44 and 720K disks? > >I don't know for sure, but were I to hazard a guess, I'd say the 720s were >1.44s that flunked the factory test procedures. > I wouldn't go around guessing about things like that. I can't find the specs for 3.5"HD disks, but essentially the differences as I understand them are similar to the differences between the standard 5.25" DS/DD diskettes and HD 5.25 diskettes. A standard 5.25" DS/DD has about a 300 oersted rating, and the HD has about 600 oersteds. A 3.5" DD has about 600 oersteds, and the HD (I believe) is higher, but I can't find the specs. The higher coercivity of the higher density disks means that you have to have a higher driving current to saturate the media. Using a low current on a high-coercivity diskette means that you don't record to the fullest and get lots of errors. Recording with a high drive current on a diskette meant for low current, will typically work on the outer tracks where the bit-density is lower, but as you go toward the center of the disk, the bit-density increases. With the low-coercivity diskettes you start getting self-erasure from the high current. This is why you get tracks locked out formating a 720k to 1.4 meg. The problem is that while the formatting is fresh and there is little magnetic decay you may get almost all the way through the disk. But as the disk ages you will be able to read less and less. With 3.5" DD's going for about 60 cents each, using two to get 1.4 meg seems a lot better than taking the chance of losing some important data. My time is worth a lot more than the 60 cents and gambling on lost data. I use REAL HD disks only to backup masters that came on HD, and use DSDD at 720k for archival. But then I think disks are so cheap. My first disks cost $4.50 each (heavily discounted) and we got 88k on them. (That was a few years before IBM made their first successful PC - there were a few tries before that fell flat!). -- Bill Vermillion - UUCP: {uiucuxc,hoptoad,petsd}!peora!tarpit!bilver!bill : bill@bilver.UUCP Please use either of the above in replies. The Reply To: may be bogus!
coleman@lll-lcc.UUCP (Sam Coleman) (08/23/89)
In article <1811@garcon.cso.uiuc.edu>, sac90286@uxa.cso.uiuc.edu (Kubla Khan) writes: > In article <1516@aws.cme.nbs.gov> durham@cme.nbs.gov (James H. Durham) writes: > >I have read a lot recently about punching/melting a hole in your average > >720K disk, then using it as a 1.44 meg disk. > > >Now I have TONS of cheap bulk > >disks (DS/DD) anc converting them over would save me a LOT of money. How > >reliable will these converted disks be... > I've been using 720K disks at 1.44M in a PS/2 with no problems. Haven't even seen any bad spots. I guess I would have a problem reading 'em on a machine that looks at the hole, but I don't plan to try. It seems to me that people will be tempted to cut holes until the prices come down-- I hate to pay $3-4 for a 1.44M disk when a $1.50 720K disk will work just as well (it's particularly aggravating when I can buy 1.2M 5.25" disks that work flawlessly for 50 cents each. Sam Coleman
brianr@phred.UUCP (Brian Reese) (08/23/89)
In article <1516@aws.cme.nbs.gov> durham@cme.nbs.gov (James H. Durham) writes: >I have read a lot recently about punching/melting a hole in your average >720K disk, then using it as a 1.44 meg disk. Now I have TONS of cheap bulk >disks (DS/DD) anc converting them over would save me a LOT of money. How >reliable will these converted disks be... and, besides cosmetically, what >are the differences between 1.44 and 720K disks? > >Thanks in advance!! The difference is the hole! I have a friend who was faced with the same problem. After a little investigation, he discovered that his drive has a little switch that detects the presence of the hole, and reads it as a 1.44M. By shorting out the switch on the drive, it fools the drive into thinking any disk is a 1.44M. This does involve removing the drive and adding a jumper, but it sounds alot easier than drilling/melting holes in hundreds of disks. (To date, he has had no problems reading/writing to both 720K and 1.44M disks.) -- Brian Reese "Tickling the 8088's"