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pl85
August 26th, 2006, 02:26 PM
OK... a friend of mine, has an old IBM PS/2 model 25, 8086-based, and it comes with 3.5in 720K DD floppy disk. BTW, the machine doesn't have hard disk...

Now my friend wants to give the PS/2 to me... But I DONT HAVE ANY 3.5 720KB DD DISKS.... I only have the 1.44 MB floppy disks... in my country, nobody has any 720KB disk....What can i do??? Can the 8088 and 8086-based computers work with the 1.44 MB floppy disk???

BTW, anybody has this machine??? what can i do if something goes wrong?? (keyboard, floppy disk)... Is it easy to add a new hard disk/other upgrades????

Thank you fo' the answer...

bbcmicro
August 26th, 2006, 02:55 PM
I think you can tape over the hole in the corner of a 1.44mb disk. Not the write protect tab, but the other one opposite. This will make the drive think it is a 720kb disk.

chuckcmagee
August 26th, 2006, 03:01 PM
Yes indeed. Covering up the opposite hole (from the sliding write protect side) will do it. Try and use something opaque. Some drives use light to detect if hole is present, some use a little pressure sensor (microswitch) so dark tape handles both situations. I used to use those silver write protect tape square from 5 1/4" disks. I had sheets of em at the time.

bbcmicro
August 26th, 2006, 03:22 PM
I have loads of those. I never use em.

dongfeng
August 26th, 2006, 03:47 PM
720kB disks are very cheap on eBay...

mbbrutman
August 26th, 2006, 06:46 PM
I think you can tape over the hole in the corner of a 1.44mb disk. Not the write protect tab, but the other one opposite. This will make the drive think it is a 720kb disk.

Don't do this! This is bad advice!

The media of a double density 720K diskette is different than the media of a 1.44MB high density disk. If you do what you suggested, it may work but you'll get lots of bad sectors and you will lose data.

This has been discussed here many times before ...

chuckcmagee
August 26th, 2006, 08:11 PM
Yep, I forgot about the media being somewhat different. Looks like 720K disks use less power to read and write than a 1440k does. So, guess it's time to pay outrageous shipping on eBay. I spotted some 720K amiga disks with little effort.

Luke
August 27th, 2006, 02:09 AM
You can easily buy DD 3.5 in. disks on auction service.
Try to find Amiga 3.5 in. disks, they are the same, format 'em on PC and you got right media.
Note, that Windows XP won't read or write at such floppies.
I don't know how it's with ME>.

DOS machine with 1.44 floppy will write/read those disks without any problems.

PS/2 as I remember use MCA bus (?), that cards aren't easy to find.
Maybe it have ISA slots?

modem7
August 27th, 2006, 02:28 AM
You can easily buy DD 3.5 in. disks on auction service.
Try to find Amiga 3.5 in. disks, they are the same, format 'em on PC and you got right media.
Note, that Windows XP won't read or write at such floppies.

XP won't read/write 720K diskettes. Are you sure about that?

Terry Yager
August 27th, 2006, 03:48 AM
I've never had any problem reading/writing 720K disks on HD media. I've never had to cover the holes on the disks, just use the /f:720 switch with the 'format' command.

--T

NathanAllan
August 27th, 2006, 03:52 AM
He's right, XP doesn't work with 720k. There is a deep-rooted solution, possibly...

http://www.softwaretipsandtricks.com/forum/windows-xp/12300-win-xp-pro-wont-format-720k-floppy.html

mbbrutman
August 27th, 2006, 06:43 AM
I've never had any problem reading/writing 720K disks on HD media. I've never had to cover the holes on the disks, just use the /f:720 switch with the 'format' command.

--T

That's because you're doing something different.

You can lay a 720K format on a high density (1.44MB) disk. You are just not using all of the capacity of the disk when you do that. A 720K format uses 9 sector per track instead of 18.

But if you take a real double density diskette and tell the hardware (by fooling it with tape) that it is a high density diskette, it'll use the wrong amount of current to write the data onto the media.

The format of the disk is separate from the media - two different issues. The media does influence what formats you can lay on a disk. You can always put less data on a disk than it was designed for, but usually you can't put much more on.

There are tricks such as squeezing a few extra sectors in, but you just can't say 'I want 18 sectors on this physical media which was designed for 8 or 8.'

carlsson
August 27th, 2006, 12:04 PM
But if you take a real double density diskette and tell the hardware (by fooling it with tape) that it is a high density diskette, it'll use the wrong amount of current to write the data onto the media.
Actually, the suggestion was the other way around. To "convert" a HD floppy to a DD, put a piece of tape. It may give bad results, in particular if the destination drive doesn't know what a HD floppy is.

To "convert" a DD floppy to HD by drilling a hole into the plastic is even worse. I know some people did this in the early 90's, but it was doomed to fail.

The question is if you manage to format 720K out of a HD floppy, will the PS/2 be able to read it? If you get genuine DD floppies, they should be possible to write on a "modern" mechanism and read back on the PS/2.

mbbrutman
August 27th, 2006, 01:41 PM
Actually, the suggestion was the other way around. To "convert" a HD floppy to a DD, put a piece of tape. It may give bad results, in particular if the destination drive doesn't know what a HD floppy is.


I don't think the distinction matters for this conversation. It's just a bad idea.

Either way, if you trick the drive into writing incorrectly on the media, you are going to get bad results. Double density is not the same as high density, and it doesn't matter if you are making holes or using tape - the problem is going to be the same.

compu_85
August 27th, 2006, 04:51 PM
I had no idea this was a problem. I've used modern 1.44 disks formatted to 400k in my Lisa without problems... yes it is picky sometimes and it doesn't like 'worn' media. But I can tell you that I loaded both the Office System and the Pascal workshop onto it with 1.44 disks with tape over the corner.

With how easy it is to get 1.44 disks (I've had boxes and boxes given to me), why not just try several? What's the worst that'll happen? It doesn't work? Just format it back to 1.44 (or throw it away) and try another disk ;-) Unless they use a different type of surface on the disk (which they must not as 1.44 drives read 720k disks) you won't damage anything... at worst it just won't work.

-Jason

mbbrutman
August 27th, 2006, 06:08 PM
The worst is that you will lose your data, and that is highly probable too.

If it's important enough to write to disk, why not just find real double density 1.0MB (raw) diskettes to use?

modem7
August 28th, 2006, 04:55 AM
He's right, XP doesn't work with 720k. There is a deep-rooted solution, possibly...
My machine runs XP and has a 1.44MB diskette drive (set in the BIOS as 1.44MB).
It reads/writes 720K diskettes (real ones: blue DS/DD) no problems at all.
To format them, I bring up a CMD prompt and run FORMAT as follows:

C:\>format a: /fs:fat
Insert new disk for drive A:
and press ENTER when ready...
The type of the file system is FAT.
Verifying 720K
Initializing the File Allocation Table (FAT)...
Volume label (11 characters, ENTER for none)?
Format complete.

730,112 bytes total disk space.
1,024 bytes in bad sectors.
729,088 bytes available on disk.

1,024 bytes in each allocation unit.
712 allocation units available on disk.

12 bits in each FAT entry.

Volume Serial Number is 94E7-372B

Format another (Y/N)? n

Vlad
September 6th, 2006, 03:22 PM
I've gotten XP to read and write 360k 5.25 floppies and the 5.25 drive. It should have no problem working with any floppy.

-VK

pl85
September 6th, 2006, 03:25 PM
People! i got a question... Does the XT and 8088-based computers support the 3.5in 1.44 MB floppy disk?? Is it possible to upgrade an XT adding this kind of floppy disk??? Does anybody has any XT with 3.5in 1.44 MB FD????

The fact is that a friend of mine wants to give me his XT with 1x5.25in 360Kb. But it doesn't have many software installed, so i'd want to install some stuff on it. What can i do??? Bye! :D

carlsson
September 6th, 2006, 03:26 PM
Probably it depends on the chipset. It makes me wonder, how many years ago was it that the last floppy controller on an expansion card - supposedly PCI - was manufactured? Or can they still be bought? I know IDE, SATA and SCSI controllers are widely available, but in case one wants several floppies... oh well, perhaps a CatWeasel controller card can be used with a PC floppy for writing PC formats as well as more exotic ones.

Terry Yager
September 9th, 2006, 04:06 PM
The worst is that you will lose your data, and that is highly probable too.

If it's important enough to write to disk, why not just find real double density 1.0MB (raw) diskettes to use?

Agreed! Best to use the 'correct' media when possible, but in a pinch...

--T