RStallworthy@HIS-PHOENIX-MULTICS.ARPA (05/12/88)
....{from RStallworthy%PCO@BCO-Multics}
RE: Non-IBM 3.5" 1.44 mb Diskette Drives
I have recently acquired from PC-Limited a 3.5" 1.44mb diskette drive
(apparently made by Sanyo). However, the unit checks for a hole at a certain
location on the dikette (near lower right corner) and if the hole is not found
then the drive will not read, write or format in high density (1.44mb) mode. I
was told by PC-Limited that this is standard. On a PS2 model 80, there is no
check for this hole, and it is possible to format and write on diskettes
without this hole. Although the diskettes without the hole are almost four
times cheaper, I have a friend who has formatted many of these diskettes on
his PS2 model 80 all at 1.44mb and all with no bad tracks, and has encountered
no problems using these diskettes.
Aside from the fact that this looks like a major rip-off my drive appears to
be seriously non-IBM-compatible, since I will not be able to read any diskette
written on an IBM PS2 (without the hole -- who is going to pay four times the
cost to have a hole when they don't need one). I am surprised that I have not
heard of this before. Has no one else made this observation?ward@cfa.harvard.EDU (Steve Ward) (05/12/88)
In article <880511234502.687547@HIS-PHOENIX-MULTICS.ARPA>, RStallworthy@HIS-PHOENIX-MULTICS.ARPA writes: > ....{from RStallworthy%PCO@BCO-Multics} > > RE: Non-IBM 3.5" 1.44 mb Diskette Drives > > I have recently acquired from PC-Limited a 3.5" 1.44mb diskette drive > (apparently made by Sanyo). However, the unit checks for a hole at a certain > location on the dikette (near lower right corner) and if the hole is not found > then the drive will not read, write or format in high density (1.44mb) mode. I > was told by PC-Limited that this is standard. On a PS2 model 80, there is no > check for this hole, and it is possible to format and write on diskettes > without this hole. Although the diskettes without the hole are almost four > times cheaper, I have a friend who has formatted many of these diskettes on > his PS2 model 80 all at 1.44mb and all with no bad tracks, and has encountered > no problems using these diskettes. > There is a much greater difference than the presence or absence of a "hole" in one corner of the micro disk between those micro disks with and without the holes. The hole is present on high density micro disks designed and manufactured to format and read/write the 1.44MB (formatted capacity) bit density. The "holeless" disk is made for 720K capacity and a lower bit density (1/2 the high density). The media are electrically different. (primarily in the specified magnetic reluctance). You may find that though writing in high density to a low density disk works okay now, sometime in the future when you take the disk off the shelf and try to read it errors will pop up and the data will be "fading" from the disk. The hole or lack thereof is a marker to allow the drive to autodetect the media type because there is a difference and you should conform to the specified bit density if you want reliable data storage. It makes more sense for the drive to detect the hole and behave accordingly (its intended use) than to ignore the hole. Your friend with the PS2 is gambling with his data. The 4/1 cost difference is deplorable, but when more people use the high density micro diskettes they will come down in cost. The price difference between high density (1.2MB formatted) 5 inch disks and standard density 5 inch disks varies between about 25% - 100% (less than 2/1) and I suspect that eventually the high density 3 inch micro density disks will attain a similar price ratio to the low density 3 inch micro disks.