hundt@samadams.princeton.edu (Tom Hundt) (04/03/91)
Here I thought it was just my own fault. My Model 80 at work wouldn't exchange floppies (reliably) with my clone at home... Problems came with 720K disks especially. If I formatted a disk on one machine, there would be problems reading on the other. On other machines at work (all PS2's, mostly 80s) I could work with the diskettes formatted/written on the 80 in my office, no problem. So, I concluded that my clone's 1.44 drive was causing the problem. Sigh. Today, a colleague mentioned that he and others had had major difficulties in this area! Exchanging the 3.5" disks between PS/2s and other machines doesn't always work! So: the question is, "What's the deal?" Is there a fix for this? Are there any set circumstances under which it happens? (Or is this just in our office, which had a bad experience with VGA monitors... IBM came and replaced the whole bunch...) -Tom Hundt
nyet@nntp-server.caltech.edu (n liu) (04/03/91)
hundt@samadams.princeton.edu (Tom Hundt) writes: >Here I thought it was just my own fault. My Model 80 at work >wouldn't exchange floppies (reliably) with my clone at home... >Problems came with 720K disks especially. If I formatted a disk >on one machine, there would be problems reading on the other. On >other machines at work (all PS2's, mostly 80s) I could work with >the diskettes formatted/written on the 80 in my office, no >problem. So, I concluded that my clone's 1.44 drive was causing >the problem. Sigh. >Today, a colleague mentioned that he and others had had major >difficulties in this area! Exchanging the 3.5" disks between >PS/2s and other machines doesn't always work! >So: the question is, "What's the deal?" >Is there a fix for this? Are there any set circumstances under >which it happens? (Or is this just in our office, which had a >bad experience with VGA monitors... IBM came and replaced the >whole bunch...) The deal (i think) is this.. PS/2 1.44 drives don't check for HD holes on disk. This means that 720K disks get formatted to 1.44M on PS/2 drives, so when you try to read them on other systems, they check the hole, find none, and assume its a 720K disk. but guess what? They're not, so you get a disk error. There are several solutions: a) format 720 disks as 720 disks (using some random format option... look it up); buy HD disks ONLY for 1.44. b) punch holes in your 720 disks (not recommended) c) set the jumper on the other systems' 1.44 drives such that they ignore the presence of the hole (like PS/2's do), so you can read 720 disks formatted incorrectly. Also, see numerous discussions in other groups for reasons not to trust 720K disks formatted as HD.. I've had enough problems with this (data dropouts) that i've moved to formatting things as suggested:) As a side note, i've heard that PS/2 drives figure out the format by reading the first two tracks HD.. if they're the same, it assumes its a 720 disk, if different, assume its HD. Formatting will ALWAYS assume its HD. Anybody else have comments on this? I'm still not sure if i got this stuff straight yet.
martyz@ted.cs.uidaho.edu (04/05/91)
In article <1991Apr3.081927.3295@nntp-server.caltech.edu> nyet@nntp-server.caltech.edu (n liu) writes: >hundt@samadams.princeton.edu (Tom Hundt) writes: > > >>Here I thought it was just my own fault. My Model 80 at work >>wouldn't exchange floppies (reliably) with my clone at home... >>Problems came with 720K disks especially. If I formatted a disk > ... >The deal (i think) is this.. PS/2 1.44 drives don't check for HD >holes on disk. This means that 720K disks get formatted to 1.44M It's not just the density problem. I've found that exchanging disks between PS/2's and non-PS/2's is unreliable even if the disks are formatted low density (720K). In fact, in our 80-machine lab, it is common for a disk written on one PS/2 to be unreadable by the machine next to it. If anyone has a solution, I'd like to hear it.