formatting 720K disc - UK Vintage Radio Repair and Restoration Discussion Forum

Dave Moll · 10th Mar 2012, 6:21 pm

Having attempted to format a 720K floppy disc for the first time since moving to Windows XP, I find that the FORMAT command no longer accepts the switch "/f:720". It therefore attempts to format it as 1.4M - which, inevitably, it fails to do.

Any ideas how to get round this?

AC/HL · 10th Mar 2012, 6:40 pm

You have to be a bit more specific
http://www.tomshardware.co.uk/forum/...atting-windows

Dave Moll · 10th Mar 2012, 7:22 pm

Thank you. "FORMAT A: /T:80 /N:9" makes sense - 80 tracks 9 sectors per track. Presumably all "/F:720" did was to convert internally to that anyway.

That saves having to fire up my AT (currently rather inaccessible).

Incidentally, I was interested to note that you can apparently fool a 1.4M disc into thinking it's 720K simply by "removing" the second hole. I had always thought that the media were different, but there you are.

emeritus · 11th Mar 2012, 12:34 am

In my experience they are different. I once tried formatting 1.44 disks to 720k in a 720k drive that I had got for my Amstrad PCW. The 1.44 disks have a higher coercivity and take more energy to write. Formatting did work after a fashion, but it took ages as the drive evidently kept having to go back for another go. [Covering the hole made no difference] I subsequently acquired a pile of proper 720K disks that had been sets of upgrade disks for redundant office PCs, so experimented no further. I haven't tried formatting a 1.44 disk to 720k in a 1.44/720k drive.

Dave Moll · 11th Mar 2012, 7:09 pm

Thank you for confirming what I thought. It also confirms that one shouldn't believe everything one reads on the web.

trellis · 27th Mar 2012, 8:28 pm

Well, speaking for myself, I've never had any problems using High Density 3.5" disks in Double Density drives. I've done this a lot with my BBC drives, since DD 3.5" disks became rare, and are now completely unavailable. They seem 100% reliable.

The same is NOT true of 5.25" disks. High Density 5.25" disks do not work at all in Double Density drives in my experience.

DragonForce · 15th Apr 2012, 4:59 am

Depends on several things: HD floppies ARE made from different materials than the older 720K DSDD floppies. Some drives will format an HD disk to 720K, other's won't. You CAN format a 720K floppy to 1.4M but it's pretty hit and miss and they tend to not be reliable, plus the DSDD floppy HAS to be a good quality manufacture.

My Amiga external drive (Proper Commodore slimline type) will accept and use any type of 3.5" floppy to 880K. A drive by a different maker will not and insists upon proper DSDD floppies. The drive I have attached to my Datel +D system (ZX Spectrum) will also happily use an HD type but the recording will fade after about a month unless I've used a DSDD floppy

Filling in the extra hole in an HD floppy simply stops a switch inside the drive from registering what type it is, it makes no difference to the actual floppy itself - the switch just tells the drive what type of media it installed.

mike_newcomb · 29th Apr 2012, 1:31 pm

Hi Dave,

you should not need the FORMAT /f:720 switch.

The absence of the 'extra' square hole tells the pc the floppy is Double Density.
If you are using a HD disk as DD, the 'extra' hole should be blanked with black insulating tape, as the drive's detection method can sometimes 'see' through other types of tape (e.g.clear) on occasion.

If the HD disk has already been used as HD, it may not format to DD. In which case 'break' the disk, by ejecting immediately formatting starts, but before it fails. Then try again. Also use the slowest pc you have.

I use the FORMAT /C switch as this tests bad sectors and if usable, resets them to such.

Good Luck - Mike

10th Mar 2012, 6:21 pm	#1
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,130	formatting 720K disc Having attempted to format a 720K floppy disc for the first time since moving to Windows XP, I find that the FORMAT command no longer accepts the switch "/f:720". It therefore attempts to format it as 1.4M - which, inevitably, it fails to do. Any ideas how to get round this? __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

10th Mar 2012, 6:40 pm	#2
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,643	Re: formatting 720K disc You have to be a bit more specific http://www.tomshardware.co.uk/forum/...atting-windows

10th Mar 2012, 7:22 pm	#3
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,130	Re: formatting 720K disc Thank you. "FORMAT A: /T:80 /N:9" makes sense - 80 tracks 9 sectors per track. Presumably all "/F:720" did was to convert internally to that anyway. That saves having to fire up my AT (currently rather inaccessible). Incidentally, I was interested to note that you can apparently fool a 1.4M disc into thinking it's 720K simply by "removing" the second hole. I had always thought that the media were different, but there you are. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

11th Mar 2012, 12:34 am	#4
emeritus Dekatron Join Date: Jan 2012 Location: Brentwood, Essex, UK. Posts: 5,349	Re: formatting 720K disc In my experience they are different. I once tried formatting 1.44 disks to 720k in a 720k drive that I had got for my Amstrad PCW. The 1.44 disks have a higher coercivity and take more energy to write. Formatting did work after a fashion, but it took ages as the drive evidently kept having to go back for another go. [Covering the hole made no difference] I subsequently acquired a pile of proper 720K disks that had been sets of upgrade disks for redundant office PCs, so experimented no further. I haven't tried formatting a 1.44 disk to 720k in a 1.44/720k drive. Last edited by emeritus; 11th Mar 2012 at 1:02 am.

11th Mar 2012, 7:09 pm	#5
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,130	Re: formatting 720K disc Thank you for confirming what I thought. It also confirms that one shouldn't believe everything one reads on the web. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

27th Mar 2012, 8:28 pm	#6
trellis Pentode Join Date: Mar 2010 Location: Ipswich, Suffolk, UK. Posts: 136	Re: formatting 720K disc Well, speaking for myself, I've never had any problems using High Density 3.5" disks in Double Density drives. I've done this a lot with my BBC drives, since DD 3.5" disks became rare, and are now completely unavailable. They seem 100% reliable. The same is NOT true of 5.25" disks. High Density 5.25" disks do not work at all in Double Density drives in my experience.

15th Apr 2012, 4:59 am	#7
DragonForce Retired Dormant Member Join Date: Nov 2011 Location: Bristol, UK. Posts: 168	Re: formatting 720K disc Depends on several things: HD floppies ARE made from different materials than the older 720K DSDD floppies. Some drives will format an HD disk to 720K, other's won't. You CAN format a 720K floppy to 1.4M but it's pretty hit and miss and they tend to not be reliable, plus the DSDD floppy HAS to be a good quality manufacture. My Amiga external drive (Proper Commodore slimline type) will accept and use any type of 3.5" floppy to 880K. A drive by a different maker will not and insists upon proper DSDD floppies. The drive I have attached to my Datel +D system (ZX Spectrum) will also happily use an HD type but the recording will fade after about a month unless I've used a DSDD floppy Filling in the extra hole in an HD floppy simply stops a switch inside the drive from registering what type it is, it makes no difference to the actual floppy itself - the switch just tells the drive what type of media it installed.

29th Apr 2012, 1:31 pm	#8
mike_newcomb Rest in Peace Join Date: Apr 2012 Location: West London, UK. Posts: 665	Re: formatting 720K disc Hi Dave, you should not need the FORMAT /f:720 switch. The absence of the 'extra' square hole tells the pc the floppy is Double Density. If you are using a HD disk as DD, the 'extra' hole should be blanked with black insulating tape, as the drive's detection method can sometimes 'see' through other types of tape (e.g.clear) on occasion. If the HD disk has already been used as HD, it may not format to DD. In which case 'break' the disk, by ejecting immediately formatting starts, but before it fails. Then try again. Also use the slowest pc you have. I use the FORMAT /C switch as this tests bad sectors and if usable, resets them to such. Good Luck - Mike