BBC 5.25 floppies. - UK Vintage Radio Repair and Restoration Discussion Forum

Denwynne · 27th Jun 2008, 11:19 pm

I have been given loads of used 5.25 floppies,most are ex PC stuff,i am having problems formatting them with a BBC computer for use on the Beeb, have tried in 40 and 80 track settings, can you re-format ex PC floppies for use in a BBC drive.

Courtney Louise · 28th Jun 2008, 6:45 am

Depends if they are HD or not. You can refomat the 360k pc disks without any problem if they are in good condition but the 1.2Mb ones wont work.

Andi

julie_m · 1st Jul 2008, 5:12 pm

You should be able to, BBCs used the same "soft-sector" disks (i.e., only one index hole per revolution) as the IBM PC (and I even remember wiring up a 5.25 drive out of an IBM to a Beeb!)

However, disks that have been used with one format layout may need to be bulk-erased before using them with a different format layout, especially if you are using an 80-track drive. The smaller read/write head may not be packing enough oomph.

You might have problems with disks that were originally used on a Commodore, Apple or Atari, as these machines could handle "hard-sectored" disks (with several index holes per revolution. You can easily tell which is which, just rotate the disk inside its sleeve.) This was because these machines used software techniques rather than hardware to discern the beginning of a track.

Autochanger · 1st Jul 2008, 11:03 pm

As Andi says, HD 1.2mb disks won't format in a 360k 40 track or a 720k 80 track drive, their magnetic surface has different properties (something to do with magnetic coefficients and oersteds). If the packets/boxes aren't labelled, you can tell which disks are which because high density 1.2mb disks don't have a hub ring, but the double density 40T/80T disks do. The hub ring is a stiffened ring around the centre hole, which was meant to help centre the disk in the drive as it was being clamped.

Roy

Dave Moll · 2nd Jul 2008, 11:05 am

Quote:

Originally Posted by Autochanger

high density 1.2mb disks don't have a hub ring, but the double density 40T/80T disks do.

What a useful tidbit of information. I learn something new every day.

Autochanger · 2nd Jul 2008, 4:51 pm

I'm not saying the hub ring rule is a 100% certainty, there just may have been some exceptions to the rule. I worked in IT for over 35 years (mainframes through minis to micros/desktop PCs) and I never saw a soft sector DD disk with a hub ring or vice/versa. Another give away was that DD disk surfaces tended to be a paler brown and most 1.2Mb HD disk surfaces looked much darker, almost black (presumably because of the different oxide coatings)

Roy

BGmidsUK · 2nd Jul 2008, 7:35 pm

The problems associated with using 40-track disks on 80-track drives is that, although the 80-track drive will usually work fine, due to the narrower heads they will only erase and write a track half the width of those written by drives fitted with heads only for 40-track, if you are sticking to the same capacity. This means the data in the resulting half-track "gaps" is still there and will confuse a 40-track head trying to read it!

I've not experienced problems myself using an 80-track drive to format and/or write to DD (40-track) disks though the ones subsequently used in a DD drive have been new ones, freshly formatted. These read fine

BG

Denwynne · 2nd Jul 2008, 8:08 pm

Thanks for all the help,you do tend to learn a lot by just asking,being a novice i appreciate all the answers

27th Jun 2008, 11:19 pm	#1
Denwynne Retired Dormant Member Join Date: Jun 2008 Location: Taunton UK Posts: 10	BBC 5.25 floppies. I have been given loads of used 5.25 floppies,most are ex PC stuff,i am having problems formatting them with a BBC computer for use on the Beeb, have tried in 40 and 80 track settings, can you re-format ex PC floppies for use in a BBC drive.

28th Jun 2008, 6:45 am	#2
Courtney Louise Octode Join Date: Sep 2005 Location: Welshpool, Powys, Wales Posts: 1,327	Re: BBC 5.25 floppies. Depends if they are HD or not. You can refomat the 360k pc disks without any problem if they are in good condition but the 1.2Mb ones wont work. Andi __________________ *33, 45, 78, around and around they go...*

1st Jul 2008, 5:12 pm	#3
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: BBC 5.25 floppies. You should be able to, BBCs used the same "soft-sector" disks (i.e., only one index hole per revolution) as the IBM PC (and I even remember wiring up a 5.25 drive out of an IBM to a Beeb!) However, disks that have been used with one format layout may need to be bulk-erased before using them with a different format layout, especially if you are using an 80-track drive. The smaller read/write head may not be packing enough oomph. You might have problems with disks that were originally used on a Commodore, Apple or Atari, as these machines could handle "hard-sectored" disks (with several index holes per revolution. You can easily tell which is which, just rotate the disk inside its sleeve.) This was because these machines used software techniques rather than hardware to discern the beginning of a track. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

1st Jul 2008, 11:03 pm	#4
Autochanger Retired Dormant Member Join Date: Mar 2008 Location: Leicestershire Posts: 42	Re: BBC 5.25 floppies. As Andi says, HD 1.2mb disks won't format in a 360k 40 track or a 720k 80 track drive, their magnetic surface has different properties (something to do with magnetic coefficients and oersteds). If the packets/boxes aren't labelled, you can tell which disks are which because high density 1.2mb disks don't have a hub ring, but the double density 40T/80T disks do. The hub ring is a stiffened ring around the centre hole, which was meant to help centre the disk in the drive as it was being clamped. Roy

2nd Jul 2008, 4:51 pm	#6
Autochanger Retired Dormant Member Join Date: Mar 2008 Location: Leicestershire Posts: 42	Re: BBC 5.25 floppies. I'm not saying the hub ring rule is a 100% certainty, there just may have been some exceptions to the rule. I worked in IT for over 35 years (mainframes through minis to micros/desktop PCs) and I never saw a soft sector DD disk with a hub ring or vice/versa. Another give away was that DD disk surfaces tended to be a paler brown and most 1.2Mb HD disk surfaces looked much darker, almost black (presumably because of the different oxide coatings) Roy

2nd Jul 2008, 7:35 pm	#7
BGmidsUK Retired Dormant Member Join Date: Oct 2007 Location: Leicester, UK. Posts: 809	Re: BBC 5.25 floppies. The problems associated with using 40-track disks on 80-track drives is that, although the 80-track drive will usually work fine, due to the narrower heads they will only erase and write a track half the width of those written by drives fitted with heads only for 40-track, if you are sticking to the same capacity. This means the data in the resulting half-track "gaps" is still there and will confuse a 40-track head trying to read it! I've not experienced problems myself using an 80-track drive to format and/or write to DD (40-track) disks though the ones subsequently used in a DD drive have been new ones, freshly formatted. These read fine BG

2nd Jul 2008, 8:08 pm	#8
Denwynne Retired Dormant Member Join Date: Jun 2008 Location: Taunton UK Posts: 10	Re: BBC 5.25 floppies. Thanks for all the help,you do tend to learn a lot by just asking,being a novice i appreciate all the answers